ARP not working on interface that does not have an IP
dsurovtsev at yahoo.com
Fri Sep 19 06:33:46 PDT 2003
Try to give rl0 and ADSL ip addresses from the same
net, i.e. 192.168.1.1 and 192.168.1.2. rl1 may remain
as well, PCsof your LAN should have 192.168.0.2 as
Subject: ARP not working on interface that does not
have an IP
To: <freebsd-ipfw at freebsd.org>
Message-ID: <000c01c37c84$84017080$4d00a8c0 at mickey>
Content-Type: text/plain; charset="Windows-1252"
My description is lengthy but believe me, it is a
I am trying to insert a FreeBSD Bridging Firewall into
office broadband network.
[[ ADSL modem / router (double as a NAT box) ]] <===>
[[ "rl0" FreeBSD
"rl1" ]] <===> [[ office LAN switch ]]
"rl0" is connected to the outside ADSL box and "rl1"
is connected to
the internal office LAN switch
The ADSL box has an IP of 192.168.0.1 and is the
default router for
everybody. "rl1" has an IP of 192.168.0.2 while "rl0"
does not have an IP
I have 99% of everything working, including the
passing of ARP (I am
running ipfw2 on 5.1R). The PCs on the office internal
LAN can connect to
the outside world with no problem whatsoever.
The only problem is "rl0" doesn't seem to be able to
look up the MAC
address of 192.168.0.1 (the ADSL router) through ARP
and that means any
TCP/IP connections I initiated on the FreeBSD box to
the outside world
? (192.168.0.1 at (incomplete) on rl1 [ethernet]
Looks like the system is expecting the ARP entry to
come from rl1 while
it should have been from rl0.
I ran tcpdump on "rl0" and saw both the outgoing ARP
requests from the
FreeBSD box and the ARP replies from 192.168.0.1. It
is just the
FreeBSD box never seem to get the ARP replies. This
problem stays the same
even when I run an "open" firewall so I am quite sure
it is not something
about the rules.
If I give "rl0" an IP address and leave "rl1" without
one then the
problem is reversed, i.e. "rl1" cannot get any ARP
I also tried to give "rl0" an IP address of
192.168.0.3 but "ifconfig"
wouldn't take it complaining about:
ifconfig: ioctl (SIOCAIFADDR): File exists
I also tried to give "rl0" an IP address from another
subnet (just to
fake it) say 192.168.1.1 but then FreeBSD complained
about the ARP
replies of 192.168.0.1 were coming from the "wrong
interface". It was
expecting it to come from "rl1" (who is in the network
range of 192.168.0.0)
instead of from "rl0" (who is NOT in the networking
I think I exhausted my experience here and would
really appreciate some
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