static routes and ARP

static routes and ARP

Post by Steve Bab » Sat, 13 May 2000 04:00:00


I have installed a copy of Checkpoint firewall -1 on  a linux box and have a
couple of Linux routing questions I hope you can help with.

I am trying to use ARP and wondered if anyone could give me the syntax?
is it - arp -s <real ip address> <MAC address>

Secondly how do I add a static route?

I want to route the "real address" to a "pretend" address ony my local net.

Something like route add 192.9.200.x

Does anyone know the correct syntax?



1. proxy arp & static routing tables dropped?

Hey all-

I've got two different firewall/gateway machines.  One is 2.2.8-RELEASE
on a 486; it's been up for about 8 months or more, works great.  Very
simple, uses proxy ARP & ipfw to limit access to a handful of machines.
It was easy to construct & configure, faster than Linux, etc.

Recently I've tried to do this same thing again, but with a better
budget.  Picked up a PII-400 & 2x FastEthernet cards.  Again, a very
fast machine (much faster than I thought it would be).  I installed
3.2-RELEASE on it.

The old machine was super-easy to get working with the existing
network.  I stuffed a few static routes with
  route add <host> -iface ed1
and the ARP thing just followed.

With the 3.2 box, I have to
  arp -S <host> ff:ff:ff:ff:ff:ff temp
BEFORE I do the static routing; after this, the ARPs are proxied and all
works well.  For a bit... then somehow the static route is dropped, and
as best I can tell the machine starts routing traffic through the
"outside" interface, and therefore doesn't proxy ARP requests on the

fxp0 == "outside" == existing net
fxp1 == "inside" == tiny testing-net

I do an "arp -S <host> ff:ff:ff:ff:ff:ff temp; route add <host> -iface
fxp1" and the ARP requests are proxied correctly, packets are
trasferred/blocked correctly (ipfw).  In fact, everything works GERAT.
But, over time, the route is dropped, the ARP table wiped, and it
defaults to fxp0 later (thus killing the hidden machine).

Can I force the routing table to keep some entries?

FYI: inetd, portmap, and routed are all OFF.  And I'll take
comments/criticism about my strategy.
just a guy

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