  The Linux Cipe+Masquerading mini-HOWTO
  Anthony Ciaravalo, acj@home.com
  v1.2, 21 April 1999

  How to setup a VPN using Cipe on a linux masquerading firewall.
  ______________________________________________________________________

  Table of Contents


  1. Introduction

     1.1 Copyright statement
     1.2 Disclaimer
     1.3 Feedback
     1.4 Getting the files

  2. Firewall Configuration

     2.1 VPN Network Diagram
     2.2 A little reference
     2.3 Additional notes about scripts and the VPN

  3. Machine A Specific Configuration

     3.1 /etc/cipe/options.machineB
     3.2 /etc/cipe/options.machineC
     3.3 /etc/rc.d/rc.cipe
     3.4 Gateway

  4. Machine B Specific Configuration

     4.1 /etc/cipe/options.machineA
     4.2 /etc/rc.d/rc.cipe
     4.3 Gateway

  5. Machine C Specific Configuration

     5.1 /etc/cipe/options.machineA
     5.2 /etc/rc.d/rc.cipe
     5.3 Gateway

  6. Common Machine Configuration

     6.1 /etc/cipe/ip-up
        6.1.1 Kernel 2.0, ipfwadm, cipe 1.0.x
        6.1.2 Kernel 2.1/2.2, ipchains, cipe 1.2.x
     6.2 /etc/cipe/ip-down
        6.2.1 Kernel 2.0, ipfwadm, cipe 1.0.x
        6.2.2 Kernel 2.1/2.2, ipchains, cipe 1.2.x

  7. Example masquerading firewall scripts

     7.1 Kernel 2.0, ipfwadm
     7.2 Kernel 2.1/2.2, ipchains

  8. Putting it all together

  9. Connecting to the WAN

  10. References

     10.1 Web Sites
     10.2 Documentation


  ______________________________________________________________________

  1.  Introduction

  This is the Linux Cipe+Masquerading mini-HOWTO.  It shows how to setup
  a Virtual Private Network between your LAN and other LAN's using Cipe
  on linux masquerading firewall machines.  It also shows an example
  masquerading firewall configuration.


  1.1.  Copyright statement

  C)opyright 1998, 1999 Anthony Ciaravalo, acj@home.com

  Unless otherwise stated, Linux HOWTO documents are copyrighted by
  their respective authors. Linux HOWTO documents may be reproduced and
  distributed in whole or in part, in any medium physical or electronic,
  as long as this copyright notice is retained on all copies. Commercial
  redistribution is allowed and encouraged; however, the author would
  like to be notified of any such distributions.

  All translations, derivative works, or aggregate works incorporating
  any Linux HOWTO documents must be covered under this copyright notice.
  That is, you may not produce a derivative work from a HOWTO and impose
  additional restrictions on its distribution. Exceptions to these rules
  may be granted under certain conditions; please contact the Linux
  HOWTO coordinator at the address given below.

  If you have questions, please contact Tim Bynum, the Linux HOWTO
  coordinator, at tjbynum@wallybox.cei.net or linux-
  howto@metalab.unc.edu


  1.2.  Disclaimer

  Use of the information and examples in this document is at your own
  risk.  There are many security issues involved when connecting
  networks across the internet.  Even though information is encrypted,
  an improperly configured firewall may result in a security breach.
  Precautions can be taken to protect your cipe connections, but it does
  not guarantee 100% security.  The author does not guarantee the
  information provided in this document will provide a secure networking
  environment.  Even though I have tried to be as accurate as possible
  creating this document, I am not responsible for any problems or
  damages incurred due to actions taken based on the information in this
  document.


  1.3.  Feedback

  Send questions, comments, suggestions, or corrections to acj@home.com.


  1.4.  Getting the files

  This howto was written based on Cipe versions 1.0.1 and 1.2.0.  See
  reference section for link to Cipe home page.

  2.  Firewall Configuration

  This howto assumes you already configured your kernel to support IP
  masquerade.  See references below for information on configuring your
  kernel for a linux firewall.

  2.1.  VPN Network Diagram

  This setup uses a star/hub configuration.  It will set up a cipe
  connection from Machine A to Machine B and another from Machine A to
  Machine C.

       ______________________________________________________________________

                          Machine A
                       eth0: 192.168.1.1
                       eth1: real ip 1
                      /               \
                     /                 \
            Machine B                  Machine C
          eth0: 192.168.2.1           eth0:192.168.3.1
          eth1: real ip 2             eth1: real ip 3
       ______________________________________________________________________

  2.2.  A little reference

       ______________________________________________________________________

       eth0 is the local network (fake address)
       eth1 is the internet address (real address)

       Port A is any valid port you would like to choose
       Port B is any other valid port you would like to choose

       Key A is any valid key you would like to choose  (read cipe doc for info)
       Key B is any valid key you would like to choose
       ______________________________________________________________________

  2.3.  Additional notes about scripts and the VPN

  The ip-up scripts currently only allow class c traffic through the
  cipe interface.  If you wish for machine B to communicate with Machine
  C then you will need to change the appropriate ip-up and ip-down
  scripts.  Specifically, you need to change the ptpaddr and myaddr
  netmasks.  There are two ip-up scripts, one for ipchains and one for
  ipfwadm.  Same with the ip-down scripts.  Change the appropriate
  incoming, outgoing, and forwarding cipe interface firewall rules
  netmask from /24 to /16. Any cipe firewall rule changes you make in
  ip-up for ipfwadm, make sure the ip-down script reflects the change so
  it will be properly removed from the list when the interface goes
  down.  For the ipchains file, anything added in a chain does not need
  ip-down reflection since ip-down will flush all the rules in the user
  defined chain.

  You will also need to uncomment the network route in the rc.cipe for
  Machine B and C that adds each others network to their route table.

  3.  Machine A Specific Configuration

  3.1.  /etc/cipe/options.machineB

       ______________________________________________________________________

       #uncomment 1 below
       #name for cipe 1.0.x
       #device          cip3b0
       #name for cipe 1.2.x
       device          cipcb0

       # remote internal (fake) ip address
       ptpaddr         192.168.2.1
       # my cipe (fake) ip address
       ipaddr          192.168.1.1
       # my real ip address and cipe port
       me              (real ip 1):(port A)
       # remote real ip address and cipe port
       peer            (real ip 2):(port A)
       #unique 128 bit key
       key             (Key A)
       ______________________________________________________________________

  3.2.  /etc/cipe/options.machineC

       ______________________________________________________________________

       #uncomment 1 below
       #name for cipe 1.0.x
       #device          cip3b1
       #name for cipe 1.2.x
       device          cipcb1

       # remote internal (fake) ip address
       ptpaddr         192.168.3.1
       # my cipe (fake) ip address
       ipaddr          192.168.1.1
       # my real ip address and cipe port
       me              (real ip 1):(port B)
       # remote real ip address and cipe port
       peer            (real ip 3):(port B)
       #unique 128 bit key
       key             (Key B)
       ______________________________________________________________________

  3.3.  /etc/rc.d/rc.cipe

  ______________________________________________________________________

  !#/bin/bash
  #rc.cipe  3/29/1999
  #Send questions or comments to acj@home.com.

  #Setup script path
  PATH="/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin"

  #Options filenames in cipe directory for cipe interfaces
  options="options.machineB options.machineC"

  #Automatically obtain options filenames from cipe directory
  #options=`/bin/ls /etc/cipe/options.*`

  #Uncomment 1 below for the cipe module name
  #cipemod="cip3b"        #for cipe 1.0
  cipemod="cipcb"        #for cipe 1.2

  #Check for cipe module and load if not already loaded
  grep $cipemod /proc/modules >/dev/null
  if [ "$?" = "1" ]; then
          echo Loading cipe module.
          modprobe $cipemod
          if [ "$?" = "1" ]; then
                  echo Error loading cipe module...exiting.
                  exit
          fi
  else
          echo Cipe module already loaded.
  fi

  #Remove any existing cipe interfaces
  cipeif=`cat /proc/net/dev | cut -f1 -d: | grep $cipemod`

  if [ "$cipeif" != "" ]; then
          echo Removing existing cipe interface(s).
          for i in $cipeif; do
                  ifconfig $i down
          done
  fi

  #Setup cipe interfaces
  echo -n "Setting up cipe interface(s): "
  for config in $options; do
          echo -n $config" "
          ciped -o $config
  done
  echo
  echo

  #Add routes for other remote networks via cipe interface(s)
  #route add -net x.x.x.x netmask x.x.x.x gw x.x.x.x

  ______________________________________________________________________

  3.4.  Gateway

  All machines on network 192.168.1.0 must have 192.168.1.1 as gateway.
  If you don't it will not work.


  4.  Machine B Specific Configuration

  4.1.  /etc/cipe/options.machineA

       ______________________________________________________________________

       #uncomment 1 below
       #name for cipe 1.0.x
       #device          cip3b0
       #name for cipe 1.2.x
       device          cipcb0

       #remote internal (fake) ip address
       ptpaddr         192.168.1.1
       # my cipe (fake) ip address
       ipaddr          192.168.2.1
       # my real ip address and cipe port
       me              (real ip 1):(port A)
       # remote real ip address and cipe port
       peer            (real ip 2):(port A)
       #unique 128 bit key
       key             (Key A)
       ______________________________________________________________________

  4.2.  /etc/rc.d/rc.cipe

  ______________________________________________________________________

  !#/bin/bash
  #rc.cipe  3/29/1999
  #Send questions or comments to acj@home.com.

  #Setup script path
  PATH="/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin"

  #Options filenames in cipe directory for cipe interfaces
  options="options.machineA"

  #Automatically obtain options filenames from cipe directory
  #options=`/bin/ls /etc/cipe/options.*`

  #Uncomment 1 below for the cipe module name
  #cipemod="cip3b"        #for cipe 1.0
  cipemod="cipcb"        #for cipe 1.2

  #Check for cipe module and load if not already loaded
  grep $cipemod /proc/modules >/dev/null
  if [ "$?" = "1" ]; then
          echo Loading cipe module.
          modprobe $cipemod
          if [ "$?" = "1" ]; then
                  echo Error loading cipe module...exiting.
                  exit
          fi
  else
          echo Cipe module already loaded.
  fi

  #Remove any existing cipe interfaces
  cipeif=`cat /proc/net/dev | cut -f1 -d: | grep $cipemod`

  if [ "$cipeif" != "" ]; then
          echo Removing existing cipe interface(s).
          for i in $cipeif; do
                  ifconfig $i down
          done
  fi

  #Setup cipe interfaces
  echo -n "Setting up cipe interface(s): "
  for config in $options; do
          echo -n $config" "
          ciped -o $config
  done
  echo
  echo

  #Add routes for other remote networks via cipe interface(s)
  #route add -net x.x.x.x netmask x.x.x.x gw x.x.x.x
  #route to machine C network
  #route add -net 192.168.3.0 netmask 255.255.255.0 gw 192.168.3.1
  ______________________________________________________________________

  4.3.  Gateway

  All machines on network 192.168.2.0 must have 192.168.2.1 as gateway.
  If you don't it will not work.

  5.  Machine C Specific Configuration

  5.1.  /etc/cipe/options.machineA

       ______________________________________________________________________

       #uncomment 1 below
       #name for cipe 1.0.x
       #device          cip3b0
       #name for cipe 1.2.x
       device          cipcb0

       #remote internal (fake) ip address
       ptpaddr         192.168.1.1
       # my cipe (fake) ip address
       ipaddr          192.168.3.1
       # my real ip address and cipe port
       me              (real ip 3):(port B)
       #remote real ip address and cipe port
       peer            (real ip 1):(port B)
       #unique 128 bit key
       key             (Key B)
       ______________________________________________________________________

  5.2.  /etc/rc.d/rc.cipe

  ______________________________________________________________________

  !#/bin/bash
  #rc.cipe  3/29/1999
  #Send questions or comments to acj@home.com.

  #Setup script path
  PATH="/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin"

  #Options filenames in cipe directory for cipe interfaces
  options="options.machineA"

  #Automatically obtain options filenames from cipe directory
  #options=`/bin/ls /etc/cipe/options.*`

  #Uncomment 1 below for the cipe module name
  #cipemod="cip3b"        #for cipe 1.0
  cipemod="cipcb"        #for cipe 1.2

  #Check for cipe module and load if not already loaded
  grep $cipemod /proc/modules >/dev/null
  if [ "$?" = "1" ]; then
          echo Loading cipe module.
          modprobe $cipemod
          if [ "$?" = "1" ]; then
                  echo Error loading cipe module...exiting.
                  exit
          fi
  else
          echo Cipe module already loaded.
  fi

  #Remove any existing cipe interfaces
  cipeif=`cat /proc/net/dev | cut -f1 -d: | grep $cipemod`

  if [ "$cipeif" != "" ]; then
          echo Removing existing cipe interface(s).
          for i in $cipeif; do
                  ifconfig $i down
          done
  fi

  #Setup cipe interfaces
  echo -n "Setting up cipe interface(s): "
  for config in $options; do
          echo -n $config" "
          ciped -o $config
  done
  echo
  echo

  #Add routes for other remote networks via cipe interface(s)
  #route add -net x.x.x.x netmask x.x.x.x gw x.x.x.x
  #route to machine B network
  #route add -net 192.168.2.0 netmask 255.255.255.0 gw 192.168.2.1
  ______________________________________________________________________

  5.3.  Gateway

  All machines on network 192.168.2.0 must have 192.168.2.1 as gateway.
  If you don't it will not work.

  6.  Common Machine Configuration

  6.1.  /etc/cipe/ip-up

  6.1.1.  Kernel 2.0, ipfwadm, cipe 1.0.x

  ______________________________________________________________________

  #!/bin/bash
  # ip-up <interface> <myaddr> <daemon-pid> <local> <remote> <arg>
  #3/29/1999
  #An example ip-up script for the older 1.x 2.x kernels using ipfwadm that
  #will setup routes and firewall rules to connect your local class c network
  #to a remote class c network.

  #The rules are configured to prevent spoofing and stuffed routing between
  #the networks.  There are also additional security enhancements commented
  #out towards the bottom of the script.
  #Send questions or comments to acj@home.com.

  #--------------------------------------------------------------------------
  #Set some script variables
  device=$1               # the CIPE interface
  me=$2                   # our UDP address
  pid=$3                  # the daemon's process ID
  ipaddr=$4               # IP address of our CIPE device
  vptpaddr=$5              # IP address of the remote CIPE device
  option=$6               # argument supplied via options

  PATH="/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin"

  #comment/uncomment to enable/disbale kernel logging for all unauthorized
  #access attempts. Must be same as ip-down script in order to remove rules.
  log="-o"

  #--------------------------------------------------------------------------
  umask 022

  # just a logging example
  #echo "UP   $*" >> /var/adm/cipe.log

  # many systems like these pid files
  #echo $3 > /var/run/$device.pid

  #--------------------------------------------------------------------------

  #add route entry for remote cipe network
  network=`expr $ptpaddr : '\([0-9]*\.[0-9]*\.[0-9]*\.\)'`0
  route add -net $network netmask 255.255.255.0 dev $device

  #need to add route entry for host in 2.0 kernels
  route add -host $ptpaddr dev $device

  #--------------------------------------------------------------------------
  #cipe interface incoming firewall rules
  #must be inserted into list in reverse order

  #deny all other incoming packets to cipe interface
  ipfwadm -I -i deny -W $device -S 0/0 -D 0/0 $log

  #accept incoming packets from remotenet to localnet on cipe interface
  ipfwadm -I -i accept -W $device -S $ptpaddr/24 -D $ipaddr/24

  #accept incoming packets from localnet to remotenet on cipe interface
  ipfwadm -I -i accept -W $device -S $ipaddr/24 -D $ptpaddr/24

  #deny incoming packets, cipe interface, claiming to be from localnet; log
  ipfwadm -I -i deny -W $device -S $ipaddr/24 -D $ipaddr/24 $log

  #--------------------------------------------------------------------------
  #cipe interface outgoing firewall rules
  #must be inserted into list in reverse order
  #deny all other outgoing packets from cipe interface
  ipfwadm -O -i deny -W $device -S 0/0 -D 0/0 $log

  #accept outgoing from remotenet to localnet on cipe interface
  ipfwadm -O -i accept -W $device -S $ptpaddr/24 -D $ipaddr/24

  #accept outgoing from localnet to remotenet on cipe interface
  ipfwadm -O -i accept -W $device -S $ipaddr/24 -D $ptpaddr/24

  #deny outgoing to localnet from localnet, cipe interface, deny; log
  ipfwadm -O -i deny -W $device -S $ipaddr/24 -D $ipaddr/24 $log

  #--------------------------------------------------------------------------
  #The forwarding is configured so machines on your local network do not get
  #masqueraded to the remote network.  This provides better access control
  #between networks.  Must be inserted into list in reverse order

  #deny all other forwarding through cipe interface; log
  ipfwadm -F -i deny -W $device -S 0/0 -D 0/0 $log

  #accept forwarding from remotenet to localnet on cipe interfaces
  ipfwadm -F -i accept -W $device -S $ptpaddr/24 -D $ipaddr/24

  #accept forwarding from localnet to remotenet on cipe interfaces
  ipfwadm -F -i accept -W $device -S $ipaddr/24 -D $ptpaddr/24

  #--------------------------------------------------------------------------
  #Make sure forwarding is enabled in the kernel. The kernel by default may
  #have forwarding disabled.
  /bin/echo 1 > /proc/sys/net/ipv4/ip_forward

  #--------------------------------------------------------------------------
  #Optional security enhancement - set default forward policy to
  #DENY or REJECT.  If your forwarding default policy is DENY/REJECT
  #you will need to add the following rules to your main forward chain.  It
  #is a good idea to have all default policies set for DENY or
  #REJECT.

  #define machine interfaces
  #localif="eth0"
  #staticif="eth1"                ;cable modem users
  #staticif="ppp0"                ;dialup users

  #a real sloppy way to get the peer ip address from the options file - a new
  #argument with peer ip:port passed to script would be nice.
  #both lines need to be uncommented
  #peerfile=`grep $device /etc/cipe/options.* | cut -f1 -d:`
  #peer=`grep peer $peerfile | cut -f1 -d: | awk '{print $2}'`

  #must log peer ip address for ip-down script
  #echo $peer > /var/run/$device.peerip

  #accept forwarding from localnet to remotenet on internal network interface
  #ipfwadm -F -i accept -W $localif -S $ipaddr/24 -D $ptpaddr/24
  #accept forwarding from remotenet to localnet on internal network interface
  #ipfwadm -F -i accept -W $localif -S $ptpaddr/24 -D $ipaddr/24
  #accept forwarding on staticif from me to peer
  #myaddr=`echo $me | cut -f1 -d:`
  #ipfwadm -F -i accept -W $staticif -S $myaddr -D $peer
  #--------------------------------------------------------------------------
  #Other optional security enhancement
  #block all incoming requests from everywhere to our cipe udp port
  #except our peer's udp port

  #need to determine udp ports for the cipe interfaces
  #get our udp port
  #if [ "$option" = "" ]; then
  #       myport=`echo $me | cut -f2 -d:`
  #else
  #       myport=$option
  #fi

  #get remote udp port -- peerfile variable must be set above
  #peerport=`grep peer $peerfile | cut -f2 -d:`

  #must log peer udp port for ip-down script
  #echo $peerport > /var/run/$device.peerport

  #get our ip address
  #myaddr=`echo $me | cut -f1 -d:`

  #deny and log all requests to cipe udp port must be inserted first
  #ipfwadm -I -i deny -P udp -W $staticif -S 0/0 -D $myaddr $myport $log
  #accept udp packets from peer at udp cipe port to my udp cipe port
  #ipfwadm -I -i accept -P udp -W $staticif -S $peer $peerport \
  #-D $myaddr $myport

  exit 0
  ______________________________________________________________________

  6.1.2.  Kernel 2.1/2.2, ipchains, cipe 1.2.x

  ______________________________________________________________________

  #!/bin/bash
  # ip-up <interface> <myaddr> <daemon-pid> <local> <remote> <arg>
  #3/29/1999
  #An example ip-up script for the newer 2.1/2.2 kernels using ipchains that
  #will setup routes and firewall rules to connect your local class c network
  #to a remote class c network.  This script creates 3 user defined chains
  #-input, output, and forward - for each cipe interface, based on the
  #interface name. It will then insert a rule into each of the built-in
  #input, output, and forward chains to use the user defined chains. The
  #rules are configured to prevent spoofing and stuffed routing between the
  #networks. There are also additional security enhancements commented out
  #towards the bottom of the script.
  #Send questions or comments to acj@home.com.

  #--------------------------------------------------------------------------

  #Set some script variables
  device=$1               # the CIPE interface
  me=$2                   # our UDP address
  pid=$3                  # the daemon's process ID
  ipaddr=$4               # IP address of our CIPE device
  ptpaddr=$5              # IP address of the remote CIPE device
  option=$6               # argument supplied via options

  PATH="/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin"

  #comment/uncomment to enable/disbale kernel logging for all unauthorized
  #access attempts. Must be same as ip-down script in order to remove rules.
  log="-l"

  #--------------------------------------------------------------------------
  umask 022
  # just a logging example
  #echo "UP   $*" >> /var/adm/cipe.log

  # many systems like these pid files
  #echo $3 > /var/run/$device.pid

  #--------------------------------------------------------------------------
  #add route entry for remote cipe network
  network=`expr $ptpaddr : '\([0-9]*\.[0-9]*\.[0-9]*\.\)'`0
  route add -net $network netmask 255.255.255.0 dev $device

  #--------------------------------------------------------------------------
  #create new ipchain for cipe interface input rules
  ipchains -N $device"i"
  #flush all rules in chain (sanity flush)
  ipchains -F $device"i"
  #deny incoming packets, cipe interface, claiming to be from localnet; log
  ipchains -A $device"i" -j DENY -i $device -s $ipaddr/24 -d $ipaddr/24 $log
  #accept incoming packets from localnet to remotenet on cipe interface
  ipchains -A $device"i" -j ACCEPT -i $device -s $ipaddr/24 -d $ptpaddr/24
  #accept incoming packets from remotenet to localnet on cipe interface
  ipchains -A $device"i" -j ACCEPT -i $device -s $ptpaddr/24 -d $ipaddr/24
  #deny all other incoming packets
  ipchains -A $device"i" -j DENY -s 0/0 -d 0/0 $log

  #--------------------------------------------------------------------------
  #create new ipchain for cipe interface output rules
  ipchains -N $device"o"
  #flush all rules in chain (sanity flush)
  ipchains -F $device"o"
  #deny outgoing to localnet from localnet, cipe interface, deny; log
  ipchains -A $device"o" -j DENY -i $device -s $ipaddr/24 -d $ipaddr/24 $log
  #accept outgoing from localnet to remotenet on cipe interface
  ipchains -A $device"o" -j ACCEPT -i $device -s $ipaddr/24 -d $ptpaddr/24
  #accept outgoing from remotenet to localnet on cipe interface
  ipchains -A $device"o" -j ACCEPT -i $device -s $ptpaddr/24 -d $ipaddr/24
  #deny all other outgoing packets
  ipchains -A $device"o" -j DENY -s 0/0 -d 0/0 $log

  #--------------------------------------------------------------------------
  #The forward chain is configured so machines on your local network do not
  #get masqueraded to the remote network.  This provides better access
  #control between networks.

  #create new ipchain for cipe interface forward rules
  ipchains -N $device"f"
  #flush all rules in chain (sanity flush)
  ipchains -F $device"f"
  #accept forwarding from localnet to remotenet on cipe interfaces
  ipchains -A $device"f" -j ACCEPT -i $device -s $ipaddr/24 -d $ptpaddr/24
  #accept forwarding from remotenet to localnet on cipe interfaces
  ipchains -A $device"f" -j ACCEPT -i $device -s $ptpaddr/24 -d $ipaddr/24
  #deny all other forwarding; log
  ipchains -A $device"f" -j DENY -s 0/0 -d 0/0 $log

  #--------------------------------------------------------------------------
  #Make sure forwarding is enabled in the kernel. New kernels by default have
  #forwarding disabled.
  /bin/echo 1 > /proc/sys/net/ipv4/ip_forward

  #--------------------------------------------------------------------------
  #insert rules to main input, output, and forward chains to enable new rules
  #for the cipe interface
  ipchains -I input -i $device -j $device"i"
  ipchains -I output -i $device -j $device"o"
  ipchains -I forward -i $device -j $device"f"

  #--------------------------------------------------------------------------
  #Optional security enhancement - set built-in forward chain policy to
  #DENY or REJECT.  If your main forward chain default policy is DENY/REJECT
  #you will need to add the following rules to your main forward chain.  It
  #is a good idea to have all built-in chain default policies set for DENY or
  #REJECT.

  #define machine interfaces
  #localif="eth0"
  #staticif="eth1"                ;cable modem users
  #staticif="ppp0"                ;dialup users

  #a real sloppy way to get the peer ip address from the options file - a new
  #argument with peer ip:port passed to script would be nice.
  #both lines need to be uncommented
  #peerfile=`grep $device /etc/cipe/options.* | cut -f1 -d:`
  #peer=`grep peer $peerfile | cut -f1 -d: | awk '{print $2}'`

  #must log peer ip address for ip-down script
  #echo $peer > /var/run/$device.peerip

  #accept forwarding from localnet to remotenet on internal network interface
  #ipchains -I forward -j ACCEPT -i $localif -s $ipaddr/24 -d $ptpaddr/24
  #accept forwarding from remotenet to localnet on internal network interface
  #ipchains -I forward -j ACCEPT -i $localif -s $ptpaddr/24 -d $ipaddr/24
  #accept forwarding on staticif from me to peer
  #myaddr=`echo $me | cut -f1 -d:`
  #ipchains -I forward -j ACCEPT -i $staticif -s $myaddr -d $peer
  #--------------------------------------------------------------------------
  #Other optional security enhancement
  #block all incoming requests from everywhere to our cipe udp port
  #except our peer's udp port

  #need to determine udp ports for the cipe interfaces
  #get our udp port
  #if [ "$option" = "" ]; then
  #       myport=`echo $me | cut -f2 -d:`
  #else
  #       myport=$option
  #fi

  #get remote udp port -- peerfile variable must be set above
  #peerport=`grep peer $peerfile | cut -f2 -d:`

  #must log peer udp port for ip-down script
  #echo $peerport > /var/run/$device.peerport

  #get our ip address
  #myaddr=`echo $me | cut -f1 -d:`

  #deny and log all requests to cipe udp port must be inserted first
  #ipchains -I input -j DENY -p udp -i $staticif -s 0/0 \
  #-d $myaddr $myport $log
  #accept udp packets from peer at udp cipe port to my udp cipe port
  #ipchains -I input -j ACCEPT -p udp -i $staticif -s $peer $peerport \
  # -d $myaddr $myport

  #--------------------------------------------------------------------------
  # Set up spoofing protection in kernel as an additional security measure
  #--------------------------------------------------------------------------
  #Why do I have spoofing protection in the firewall rules in addition to
  #this script that sets up spoof protection for each interface in the
  #kernel? Guess I'm paranoid.

  if [ -e /proc/sys/net/ipv4/conf/all/rp_filter ]; then
          echo -n "Setting up IP spoofing protection..."
          iface="/proc/sys/net/ipv4/conf/$device/rp_filter"
          echo 1 > $iface
          echo "done."
  else
          echo "Cannot setup spoof protection in kernel for $device" \
                  | mail -s"Security Warning: $device" root
          exit 1
  fi

  exit 0
  ______________________________________________________________________

  6.2.  /etc/cipe/ip-down

  6.2.1.  Kernel 2.0, ipfwadm, cipe 1.0.x

  ______________________________________________________________________

  #!/bin/bash

  # ip-down <interface> <myaddr> <daemon-pid> <local> <remote> <arg>
  #3/29/1999
  #An example ip-down script for the older 1.x 2.x kernels using ipfwadm that
  #will remove firewall rules that were setup to connect your local class c
  #network to a remote class c network.

  #--------------------------------------------------------------------------
  #Set some script variables
  device=$1               # the CIPE interface
  me=$2                   # our UDP address
  pid=$3                  # the daemon's process ID
  ipaddr=$4               # IP address of our CIPE device
  ptpaddr=$5              # IP address of the remote CIPE device
  option=$6               # argument supplied via options

  PATH="/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin"

  #comment/uncomment to enable/disbale kernel logging for all unauthorized
  #access attempts. Must be same as ip-down script in order to remove rules.
  log="-o"

  #--------------------------------------------------------------------------
  umask 022

  # just a logging example
  #echo "DOWN   $*" >> /var/adm/cipe.log

  # many systems like these pid files
  #rm -f /var/run/$device.pid

  #--------------------------------------------------------------------------
  #cipe interface incoming firewall rules

  #delete (deny all other incoming packets to cipe interface)
  ipfwadm -I -d deny -W $device -S 0/0 -D 0/0 $log

  #delete (accept incoming packets from remotenet to localnet on cipe
  #interface)
  ipfwadm -I -d accept -W $device -S $ptpaddr/24 -D $ipaddr/24

  #delete (accept incoming packets from localnet to remotenet on cipe
  #interface)
  ipfwadm -I -d accept -W $device -S $ipaddr/24 -D $ptpaddr/24

  #delete (deny incoming packets, cipe interface, claiming to be from
  #localnet and log)
  ipfwadm -I -d deny -W $device -S $ipaddr/24 -D $ipaddr/24 $log

  #--------------------------------------------------------------------------
  #cipe interface incoming firewall rules

  #delete (deny all other outgoing packets from cipe interface)
  ipfwadm -O -d deny -W $device -S 0/0 -D 0/0 $log

  #delete (accept outgoing from remotenet to localnet on cipe interface)
  ipfwadm -O -d accept -W $device -S $ptpaddr/24 -D $ipaddr/24

  #delete (accept outgoing from localnet to remotenet on cipe interface)
  ipfwadm -O -d accept -W $device -S $ipaddr/24 -D $ptpaddr/24

  #delete (deny outgoing to localnet from localnet, cipe interface, deny
  #and log)
  ipfwadm -O -d deny -W $device -S $ipaddr/24 -D $ipaddr/24 $log

  #--------------------------------------------------------------------------
  #cipe interface forwarding firewall rules

  #delete (deny all other forwarding through cipe interface; log)
  ipfwadm -F -d deny -W $device -S 0/0 -D 0/0 $log

  #delete (accept forwarding from remotenet to localnet on cipe interfaces)
  ipfwadm -F -d accept -W $device -S $ptpaddr/24 -D $ipaddr/24

  #delete (accept forwarding from localnet to remotenet on cipe interfaces)
  ipfwadm -F -d accept -W $device -S $ipaddr/24 -D $ptpaddr/24

  #--------------------------------------------------------------------------
  #Optional security enhancement - set default forward policy to
  #DENY or REJECT.  If your forwarding default policy is DENY/REJECT
  #you will need to add the following rules to your main forward chain.  It
  #is a good idea to have all default policies set for DENY or
  #REJECT.

  #define machine interfaces
  #localif="eth0"
  #staticif="eth1"                ;cable modem users
  #staticif="ppp0"                ;dialup users

  #a real sloppy way to get the peer ip address from the options file - a new
  #argument with peer ip:port passed to script would be nice.
  #both lines need to be uncommented
  #peerfile=`grep $device /etc/cipe/options.* | cut -f1 -d:`
  #peer=`grep peer $peerfile | cut -f1 -d: | awk '{print $2}'`

  #must log peer ip address for ip-down script
  #echo $peer > /var/run/$device.peerip

  #delete (accept forwarding from localnet to remotenet on internal network
  interface)
  #ipfwadm -F -d accept -W $localif -S $ipaddr/24 -D $ptpaddr/24
  #delete (accept forwarding from remotenet to localnet on internal network
  interface)
  #ipfwadm -F -d accept -W $localif -S $ptpaddr/24 -D $ipaddr/24
  #delete (accept forwarding on staticif from me to peer)
  #myaddr=`echo $me | cut -f1 -d:`
  #ipfwadm -F -d accept -W $staticif -S $myaddr -D $peer
  #--------------------------------------------------------------------------
  #Other optional security enhancement
  #block all incoming requests from everywhere to our cipe udp port
  #except our peer's udp port

  #need to determine udp ports for the cipe interfaces
  #get our udp port
  #if [ "$option" = "" ]; then
  #       myport=`echo $me | cut -f2 -d:`
  #else
  #       myport=$option
  #fi

  #get remote udp port -- peerfile variable must be set above
  #peerport=`grep peer $peerfile | cut -f2 -d:`

  #must log peer udp port for ip-down script
  #echo $peerport > /var/run/$device.peerport

  #get our ip address
  #myaddr=`echo $me | cut -f1 -d:`

  #delete (deny and log all requests to cipe udp port must be inserted first)
  #ipfwadm -I -d deny -P udp -W $staticif -S 0/0 -D $myaddr $myport $log
  #delete (accept udp packets from peer at udp cipe port to my udp cipe port)
  #ipfwadm -I -d accept -P udp -W $staticif -S $peer $peerport \
  #-D $myaddr $myport

  exit 0
  ______________________________________________________________________

  6.2.2.  Kernel 2.1/2.2, ipchains, cipe 1.2.x

  ______________________________________________________________________

  #!/bin/sh
  # ip-down <interface> <myaddr> <daemon-pid> <local> <remote> <arg>
  #3/29/1999
  #An example ip-down script for the newer 2.1/2.2 kernels using ipchains
  #that will remove firewall rules that were setup to connect your local
  #class c network to a remote class c network.  Optional security
  #enhancement rules removal is also added and commented towards end of
  #script.
  #Send questions or comments to acj@home.com.

  #--------------------------------------------------------------------------
  #Set some script variables
  device=$1               # the CIPE interface
  me=$2                   # our UDP address
  pid=$3                  # the daemon's process ID
  ipaddr=$4               # IP address of our CIPE device
  ptpaddr=$5              # IP address of the remote CIPE device
  option=$6               # argument supplied via options
  PATH="/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin"

  #comment/uncomment to enable/disbale kernel logging for all unauthorized
  #access attempts
  #must be same as ip-up script in order to remove rules
  log="-l"

  #--------------------------------------------------------------------------
  umask 022

  # Logging example
  #echo "DOWN $*" >> /var/adm/cipe.log

  # remove the daemon pid file
  #rm -f /var/run/$device.pid

  #--------------------------------------------------------------------------
  #remove rules from main input, output, and forward chains for cipe
  #interface
  ipchains -D input -i $device -j $device"i"
  ipchains -D output -i $device -j $device"o"
  ipchains -D forward -i $device -j $device"f"

  #--------------------------------------------------------------------------
  #flush all rules in cipe interface input chain
  ipchains -F $device"i"
  #remove cipe interface input chain
  ipchains -X $device"i"

  #--------------------------------------------------------------------------
  #flush all rules in cipe interface output chain
  ipchains -F $device"o"
  #remove cipe interface output chain
  ipchains -X $device"o"

  #--------------------------------------------------------------------------
  #flush all rules in cipe interface forward chain
  ipchains -F $device"f"
  #remove cipe interface forward chain
  ipchains -X $device"f"

  #--------------------------------------------------------------------------
  #Remove optional security enhancement rules

  #get peer ip address
  #peer=`cat /var/run/$device.peerip`
  #define machine interfaces
  #localif="eth0"
  #staticif="eth1"                ;cable modem users
  #staticif="ppp0"                ;dialup users

  #get our ip address
  #myaddr=`echo $me |cut -f1 -d:`

  #delete (accept forwarding from localnet to remotenet on internal network
  #interface)
  #ipchains -D forward -j ACCEPT -i $localif -s $ipaddr/24 -d $ptpaddr/24
  #delete (accept forwarding from remotenet to localnet on internal network
  #interface)
  #ipchains -D forward -j ACCEPT -i $localif -s $ptpaddr/24 -d $ipaddr/24
  #delete (accept forwarding on staticif from me to peer)
  #ipchains -D forward -j ACCEPT -i $staticif -s $myaddr -d $peer

  #remove peer ip file
  #rm /var/run/$device.peerip

  #--------------------------------------------------------------------------
  #Remove other optional security enhancement rules

  #get peer udp port
  #peerport=`cat /var/run/$device.peerport`

  #get our udp port
  #if [ "$option" = "" ]; then
  #        myport=`echo $me | cut -f2 -d:`
  #else
  #        myport=$option
  #fi

  #delete (deny and log all requests to cipe udp port must be inserted first)
  #ipchains -D input -j DENY -p udp -i $staticif -s 0/0 \
  #-d $myaddr $myport $log
  #delete (accept udp packets from peer at udp cipe port to my udp cipe port)
  #ipchains -D input -j ACCEPT -p udp -i $staticif -s $peer $peerport \
  #-d $myaddr $myport

  #remove peer port file
  #rm /var/run/$device.peerport

  #--------------------------------------------------------------------------

  exit 0
  ______________________________________________________________________

  7.  Example masquerading firewall scripts

  7.1.  Kernel 2.0, ipfwadm

  ______________________________________________________________________

  #!/bin/sh
  #04/04/1999
  #example rc.firewall script for the 2.0 kernels using ipfwadm
  #I cant take full credit for this script.  I had found it a few
  #years ago and made slight modifications.
  #Send questions or comments to acj@home.com.

  #---------------------------------------------------------------------
  #Variables
  #---------------------------------------------------------------------

  #local ethernet interface
  localip=
  localif=eth0

  #static ethernet interface
  staticip=
  staticif=eth1

  PATH="/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin"

  #---------------------------------------------------------------------
  #Incoming Firewall Policies
  #---------------------------------------------------------------------
  #flush incoming firewall policies
  /sbin/ipfwadm -I -f

  #set incoming firewall policy default to deny
  /sbin/ipfwadm -I -p deny

  #---------------------------------------------------------------------

  #local interface, local machines, going anywhere is valid
  /sbin/ipfwadm -I -a accept -V $localip -S $localip/24 -D 0.0.0.0/0
  #remote interface, claiming to be local machines (IP spoofing) deny and log
  /sbin/ipfwadm -I -a deny -V $staticip -S $localip/24 -D 0.0.0.0/0 -o
  #remote interface, any source, going to staticip address is valid
  /sbin/ipfwadm -I -a accept -V $staticip -S 0.0.0.0/0 -D $staticip/32
  #loopback interface is valid
  /sbin/ipfwadm -I -a accept -V 127.0.0.1 -S 0.0.0.0/0 -D 0.0.0.0/0
  #all other incoming is denied and logged
  /sbin/ipfwadm -I -a deny -S 0.0.0.0/0 -D 0.0.0.0/0 -o

  #---------------------------------------------------------------------
  #Outgoing Firewall Policies
  #---------------------------------------------------------------------

  #flush outgoing firewall policies
  /sbin/ipfwadm -O -f

  #set outgoing firewall policy default to deny
  /sbin/ipfwadm -O -p deny

  #---------------------------------------------------------------------

  #local interface, any source going to local net is valid
  /sbin/ipfwadm -O -a accept -V $localip -S 0.0.0.0/0 -D $localip/24
  #outgoing to localnet on static interface, stuffed routing, deny
  /sbin/ipfwadm -O -a deny -V $staticip -S 0.0.0.0/0 -D $localip/24 -o
  #outgoing from localnet on static interface, stuffed masquerading, deny
  /sbin/ipfwadm -O -a deny -V $staticip -S $localip/24 -D 0.0.0.0/0 -o
  #outgoing to localnet on static interface, stuffed masquerading, deny
  /sbin/ipfwadm -O -a deny -V $staticip -S 0.0.0.0/0 -D $localip/24 -o
  #anything else outgoing on remote interface is valid
  /sbin/ipfwadm -O -a accept -V $staticip -S $staticip/32 -D 0.0.0.0/0
  #loopback interface is valid
  /sbin/ipfwadm -O -a accept -V 127.0.0.1 -S 0.0.0.0/0 -D 0.0.0.0/0
  #all other outgoing is denied and logged
  /sbin/ipfwadm -O -a deny -S 0.0.0.0/0 -D 0.0.0.0/0 -o

  #--------------------------------------------------------------------------
  #Forwarding firewall policies
  #--------------------------------------------------------------------------

  #flush forwarding policies
  /sbin/ipfwadm -F -f

  #set forwarding policy default to deny
  /sbin/ipfwadm -F -p deny

  #masquerade from localnet on local interface to anywhere
  /sbin/ipfwadm -F -a masquerade -W $staticif -S $localip/24 -D 0.0.0.0/0
  #all other forwarding is denied
  /sbin/ipfwadm -F -a deny -S 0.0.0.0/0 -D 0.0.0.0/0

  exit 0
  ______________________________________________________________________

  7.2.  Kernel 2.1/2.2, ipchains

  ______________________________________________________________________

  #!/bin/sh
  #04/04/1999
  #example rc.firewall script for the newer 2.1/2.2 kernels using ipchains
  #that creates user defined chains for each interface.  There are firewall
  #rules for spoofing protection which may be unnecessary since the newer
  #kernels can have kernel spoofing protection enabled.  You might say it's
  #super paranoid checking.
  #Send questions or comments to acj@home.com.

  #---------------------------------------------------------------------
  #Variables
  #---------------------------------------------------------------------

  #local ethernet interface
  localip=
  localif=eth0

  #static ethernet interface
  staticip=
  staticif=eth1

  #loopback interface
  loopback=lo

  PATH="/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin"

  #---------------------------------------------------------------------
  #Flush built-in input, output, and forward ipchains; set default policy
  #Good policy to deny all packets especially while setting up chains
  #---------------------------------------------------------------------

  #set incoming firewall policy default to deny
  ipchains -P input DENY

  #flush incoming firewall policies
  ipchains -F input

  #---------------------------------------------------------------------

  #set outgoing firewall policy default to deny
  ipchains -P output DENY

  #flush outgoing firewall policies
  ipchains -F output

  #---------------------------------------------------------------------

  #set forwarding firewall policy default to deny
  ipchains -P forward DENY

  #flush forwarding firewall policies
  ipchains -F forward

  #---------------------------------------------------------------------
  #flush all policies  -redundant for main policies, but also flushes user
  #defined policies
  #ipchains -F

  #remove all user defined policies - you may or may not want to enable this
  #ipchains -X

  #---------------------------------------------------------------------
  #Incoming Firewall Policies
  #---------------------------------------------------------------------
  #create new input chain for static ethernet interface
  ipchains -N $staticif"-i"

  #flush all rules in chain (sanity flush)
  ipchains -F $staticif"-i"

  #block incoming tcp SYN packets to all ports on staticif and log
  #this may be a little harsh but its a nice feature
  #ipchains -A $staticif"-i" -j DENY -p tcp -y -i $staticif -s 0/0 \
  #-d $staticip : -l

  #remote interface, claiming to be local machines (IP spoofing) deny and log
  ipchains -A $staticif"-i" -j DENY -i $staticif -s $localip/16 -d 0/0 -l

  #remote interface, any source, going to staticip address is valid
  ipchains -A $staticif"-i" -j ACCEPT -i $staticif -s 0/0 -d $staticip/32

  #all other incoming is denied and logged
  ipchains -A $staticif"-i" -j DENY -s 0/0 -d 0/0 -l

  #---------------------------------------------------------------------

  #create new input chain for local ethernet interface
  ipchains -N $localif"-i"

  #flush all rules in chain (sanity flush)
  ipchains -F $localif"-i"

  #local interface, local machines, going anywhere is valid
  ipchains -A $localif"-i" -j ACCEPT -i $localif -s $localip/24 -d 0/0

  #all other incoming is denied and logged
  ipchains -A $localif"-i" -j DENY -s 0/0 -d 0/0 -l

  #---------------------------------------------------------------------

  #create new input chain for loopback interface
  ipchains -N $loopback"-i"

  #flush all rules in chain (sanity flush)
  ipchains -F $loopback"-i"

  #loopback interface is valid
  ipchains -A $loopback"-i" -j ACCEPT -i $loopback -s 0/0 -d 0/0

  #all other incoming is denied and logged
  ipchains -A $loopback"-i" -j DENY -s 0/0 -d 0/0 -l

  #--------------------------------------------------------------------------
  #Forwarding firewall policies
  #--------------------------------------------------------------------------

  #create new forward chain for static ethernet interface
  ipchains -N $staticif"-f"

  #flush all rules in chain (sanity flush)
  ipchains -F $staticif"-f"

  #masquerade from localnet on static interface to anywhere
  ipchains -A $staticif"-f" -j MASQ -i $staticif -s $localip/24 -d 0/0

  #all other forwarding is denied and logged
  ipchains -A $staticif"-f" -j DENY -s 0/0 -d 0/0 -l

  #---------------------------------------------------------------------

  #create new forward chain for local ethernet interface
  ipchains -N $localif"-f"

  #flush all rules in chain (sanity flush)
  ipchains -F $localif"-f"

  #all other forwarding is denied and logged
  ipchains -A $localif"-f" -j DENY -s 0/0 -d 0/0 -l

  #---------------------------------------------------------------------

  #create new forward chain for loopback interface
  ipchains -N $loopback"-f"

  #flush all rules in chain (sanity flush)
  ipchains -F $loopback"-f"

  #all other forwarding is denied and logged
  ipchains -A $loopback"-f" -j DENY -s 0/0 -d 0/0 -l


  #---------------------------------------------------------------------
  #Outgoing Firewall Policies
  #---------------------------------------------------------------------

  #create new output chain for static ethernet interface
  ipchains -N $staticif"-o"

  #flush all rules in chain (sanity flush)
  ipchains -F $staticif"-o"

  #outgoing to localnet on remote interface(stuffed routing) deny & log
  ipchains -A $staticif"-o" -j DENY -i $staticif -s 0/0 -d $localip/24 -l

  #outgoing from local net on remote interface, stuffed masquerading, deny
  ipchains -A $staticif"-o" -j DENY -i $staticif -s $localip/24 -d 0/0 -l

  #anything else outgoing on remote interface is valid
  ipchains -A $staticif"-o" -j ACCEPT -i $staticif -s $staticip/32 -d 0/0

  #all other outgoing is denied and logged
  ipchains -A $staticif"-o" -j DENY -s 0/0 -d 0/0 -l

  #---------------------------------------------------------------------

  #create new output chain for local ethernet interface
  ipchains -N $localif"-o"

  #flush all rules in chain (sanity flush)
  ipchains -F $localif"-o"

  #local interface, any source going to local net is valid
  ipchains -A $localif"-o" -j ACCEPT -i $localif -s 0/0 -d $localip/24

  #all other outgoing is denied and logged
  ipchains -A $localif"-o" -j DENY -s 0/0 -d 0/0 -l

  #---------------------------------------------------------------------

  #create new output chain for loopback interface
  ipchains -N $loopback"-o"

  #flush all rules in chain (sanity flush)
  ipchains -F $loopback"-o"

  #loopback interface is valid
  ipchains -A $loopback"-o" -j ACCEPT -i $loopback -s 0/0 -d 0/0
  #all other outgoing is denied and logged
  ipchains -A $loopback"-o" -j DENY -s 0/0 -d 0/0 -l

  #--------------------------------------------------------------------------
  #make sure forwarding is enabled in the kernel
  #--------------------------------------------------------------------------

  /bin/echo 1 > /proc/sys/net/ipv4/ip_forward

  #--------------------------------------------------------------------------
  #Add pointers to built-in chains to enable user defined chains
  #change the order in each chain to optimize filtering for an interface
  #--------------------------------------------------------------------------

  #add local interface input chain
  ipchains -A input -i $localif -j $localif"-i"

  #add static interface input chain
  ipchains -A input -i $staticif -j $staticif"-i"

  #add loopback interface input chain
  ipchains -A input -i $loopback -j $loopback"-i"

  #-------------------------------------------------------------------------

  #add local interface output chain
  ipchains -A output -i $localif -j $localif"-o"

  #add static interface output chain
  ipchains -A output -i $staticif -j $staticif"-o"

  #add loopback interface output chain
  ipchains -A output -i $loopback -j $loopback"-o"

  #-------------------------------------------------------------------------

  #add local interface forward chain
  ipchains -A forward -i $localif -j $localif"-f"

  #add static interface forward chain
  ipchains -A forward -i $staticif -j $staticif"-f"

  #add loopback interface forward chain
  ipchains -A forward -i $loopback -j $loopback"-f"

  #---------------------------------------------------------------------
  #Super Paranoid check --- even though default policy is set for deny,
  #block all packets on any interface
  #---------------------------------------------------------------------

  #all other incoming is denied and logged
  ipchains -A input -j DENY -s 0/0 -d 0/0 -l

  #all other output is denied and logged
  ipchains -A output -j DENY -s 0/0 -d 0/0 -l

  #all other forwarding is denied and logged
  ipchains -A forward -j DENY -s 0/0 -d 0/0 -l

  exit 0
  ______________________________________________________________________

  8.  Putting it all together

  This is an example rc.local script to start everything when your
  system boots.  It will add spoofing protection in the kernel if you
  are using a 2.2 kernel, setup the masquerading firewall policies, and
  start the cipe interface(s).

       ______________________________________________________________________

       #!/bin/bash
       #4/4/99
       #an example rc.local script
       #Send questions or comments to acj@home.com

       echo

       #Set up spoof protection in kernel -- from IPChains HOWTO by Paul Russell

       #this is only for the newer 2.1/2.2 kernels

       #if [ -e /proc/sys/net/ipv4/conf/all/rp_filter ]; then
       #   echo -n "Setting up IP spoofing protection..."
       #   for f in /proc/sys/net/ipv4/conf/*/rp_filter; do
       #       echo 1 > $f
       #   done
       #   echo "done."
       #else
       #   echo PROBLEMS SETTING UP IP SPOOFING PROTECTION.  BE WORRIED.
       #   echo "CONTROL-D will exit from this shell and continue system startup."
       #   echo
       #   # Start a single user shell on the console
       #   /sbin/sulogin $CONSOLE
       #fi

       echo

       #Setup firewall policies
       if [ -x /etc/rc.d/rc.firewall ]; then
               echo Setting up firewall packet filtering policies.
               echo
               . /etc/rc.d/rc.firewall
       fi

       #Start cipe interfaces
       if [ -x /etc/rc.d/rc.cipe ]; then
               echo Starting VPN interfaces.
               . /etc/rc.d/rc.cipe
       fi

       exit 0
       ______________________________________________________________________

  9.  Connecting to the WAN

  At this point your cipe interface should be up and running.  Try
  pinging machines on the other network(s).  If you cannot ping check
  the following on the firewall machine:


  ·  Check that forwarding is enabled in the kernel.

  ·  Do an ifconfig to check if the cipe interface is up.

       cipcb0  Link encap:IPIP Tunnel  HWaddr
               inet addr:192.168.1.1  P-t-P:192.168.2.1  Mask:255.255.255.255
               UP POINTOPOINT NOTRAILERS RUNNING NOARP  MTU:1442  Metric:1
               RX packets:28163 errors:6 dropped:0 overruns:0 frame:6
               TX packets:29325 errors:0 dropped:0 overruns:0 carrier:0
               collisions:0 txqueuelen:100

  ·  Check the route table for a host entry for the other cipe host on
     the cipe interface.

       192.168.2.1    *      255.255.255.255 UH    0   0        0 cipcb0

  ·  Check the route table for a network entry to the other network(s)
     on the cipe interface.

       192.168.2.0    *      255.255.255.0   U     0   0        0  cipcb0

  ·  Check the log files for any error messages.

  If your other machines behind your firewall cannot access machines
  behind the other firewall check that the gateway is properly setup on
  both ends.

  Once you are able to ping, ftp, telnet, etc. to machines on the other
  network, the next step is to get your networks to see each other and
  access each other using SAMBA browsing.  A few hints: lmhosts or wins
  server is required, trusted domains for NT.  I have set these up, but
  that is not the purpose of this document (at least not for now).

  If you used the example firewall masquerading script, then all of your
  machines should also be able to connect to the internet.  If you
  cannot, then you might want to check the log files.  You may also want
  to try using tcpdump to see what is happening with the packets.

  10.  References

  10.1.  Web Sites

  Cipe Home Page <http://sites.inka.de/~bigred/devel/cipe.html>

  Masq Home Page <http://ipmasq.cjb.net>

  Samba Home Page <http://samba.anu.edu.au>

  Linux HQ <http://www.linuxhq.com>  ---great site for lots of linux
  info

  10.2.  Documentation

  cipe.info: info file included with cipe distribution

  Firewall HOWTO, by Mark Grennan, markg@netplus.net

  IP Masquerade mini-HOWTO,by  Ambrose Au, ambrose@writeme.com

  IPChains-Howto, by Paul Russell, Paul.Russell@rustcorp.com.au

