Using PPP and Proxy arp


DESCRIPTION:  How do you set up proxy arp for PPP.


Using Proxy ARP with a PPP Connection


When a user dials into a network, it is sometimes usefull to have the user
become a part of the local subnet. This can be accomplished with a proxy
arp, and by setting up the local address of the PPP server at the same
address of the network interface. For example:

   * System One has a token ring address of
   * The Subnet for the system is
   * The hardware address for System One is: 10.0.5a.a8.84.9d
   * The Desired remote (dial in) system address is


For more detail on creating a server, see the PPP cookbook.

  1. Add the PPP Link for the server.
        o smit ppp
        o Link Control Configuration
        o Add a Link Configuration
        o Fill at least the following fields:
             + PPP subsystem name: Unique name up to 25 chars
             + max server connections: At least 1.
             + max client connections: 0 for server, unless also a client.
             + max ip interfaces: At least 1, (Server + client)
             + max async hdlc attachments: At least 1, Number of active
        o Hit enter to add Link
  2. Add the PPP IP server address.
        o smit ppp
        o PPP IP Interfaces
        o Add a Server Interface
        o FIll in the following fields:
             + Local IP address: Make this the same as your token ring
             + Staring Remote IP address: Desired remote address.
             + Number of addresses: At least one, For example use 1.
             + Netmask: Use netmask of local subnet
        o Hit enter ot add the IP Server Interface.
  3. Add an entry in the /etc/hosts file for the remote system(s)
     Example: myppp
  4. Find the hardware address of the local adapter with netstat -i

     Name  Mtu   Network     Address            Ipkts Ierrs    Opkts Oerrs  Coll
     lo0   16896                              3000580     0  3000580     0     0
     lo0   16896 127         localhost        3000580     0  3000580     0     0
     tr0   1492        10.0.5a.a8.84.9d      65426841     0  2019080     0     0
     tr0   1492  9.19.128    tesch.aix.dfw.i 65426841     0  2019080     0     0

  5. Turn on ipforwarding with: no ipforwarding=1
  6. Add an arp entry for the remote host.
        o Format: arp -s type hostname hardware address [temp] [pub]
        o Example: arp -s 802.5 myppp 10:00:5a:a8:84:9d pub
             + The type (802.5) is the type of the adapter card that will
               respond the the request. Types: ether, 802.3, fddi, 802.5.
             + hostname: name entered in /etc/hosts table.
             + hardware address from netstat -i (with colon separaters).
             + pub makes it public, temp would make it only temporary. You
               may have to add this arp command to /etc/ to hold over
        o netstat -i will now show:

          pp0   1500                              15     0       91     0     0
          pp0   1500  9.19.128    tesch.aix.dfw.i       15     0       91     0     0

  7. Dial in from client system - see cookbook.
     If this is an AIX client use:
     /usr/sbin/pppattachd ttyX client connect "/usr/sbin/pppdial -v -f
  8. ifconfig pp0 will tell you when the link is up.

     pp0: flags=71
             inet --> netmask 0xfffff000

  9. Look at the the routing table with netstat -rn

     Routing tables
     Destination      Gateway            Flags     Refs     Use  Interface
     (0) 0 ffff ff00

     Route Tree for Protocol Family 2:
     default       UG          4   216655  tr0
     9.19.128        U          32  4602124  tr0        UH          2      101  pp0
     127              U           1      502  lo0

 10. Users anywhere on the local network will now be able to use the

Support Line: Using PPP and Proxy arp ITEM: BJ8586L
Dated: June 1996 Category: N/A
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