*BSD News Article 93830


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From: Tony Griffiths <tonyg@OntheNet.com.au>
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: How to use two Ethernet cards in FreeBSD.
Date: Fri, 18 Apr 1997 18:07:22 +1000
Organization: On the Net (ISP on the Gold Coast, Australia)
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To: Valentine Gogichashvili <valgog@hotmail.com>
Xref: euryale.cc.adfa.oz.au comp.unix.bsd.freebsd.misc:39274

Valentine Gogichashvili wrote:
> 
> Hi,
> 
> I have installed FreeBSD and connected my LAN into Internet whit it.
> 
> But I have to connect another branch of our LAN throw another Ethernet card
> (ed1).
> 
> The problem is that i can not make route to hosts on ed1 branch, and, for
> example, when host on ed1 gives the request to my FreeBSD box by ping or
> telnet, the replay is going through ed0.

A bit more info on the IP addressing you are using might help,
however...

Firstly, you need to make sure that the FreeBSD system is acting as a
router (ie. IP forwarding is set to 1 via sysctl or your /etc/sysconfig
setting).

Secondly, whatever systems need to communicate with hosts on the other
LAN need to have a route for that subnet that points to the FreeBSD
box.  If both LANs are in the SAME subnet, then you have real problems
because the FreeBSD box would need to proxy arp each IP address on one
LAN to the other LAN, and vice versa!  It is much easier to simply
subnet your network address block (if they are part of the same Class C
or whatever) or run independent networks altogether (same difference
actually from an IP routing point of view!).

An example of a dual-ethernet FreeBSD box is-

root @ xxxx:/usr/local/security> netstat -rn 
Routing tables

Internet:
Destination        Gateway            Flags     Refs     Use     Netif
Expire
default            203.10.89.20       UGSc       36    34885       ed0
127.0.0.1          127.0.0.1          UH          0     3165       lo0
203.10.89          link#1             UC          0        0 
203.10.89.1        0:0:c:f6:97:c1     UHLW        0   602636       ed0
...
203.14.201.1       8:0:2b:99:91:92    UHLW        1   565971       lo0
203.14.201.2       8:0:2b:e4:c2:3d    UHLW        0   107770       le0
203.14.201.3       0:0:c0:65:84:d0    UHLW        0      104       le0
...

This system has 203.10.89.20 as it's default router on the 'ed0'
Ethernet while the Cisco has the IP address of ed0 as the path to
network 203.14.201.* on le0.  Other hosts on the 203.10.89.* network
initially forward to the Cisco which then issues an IP "redirect" back
to the real gateway for the 203.14.201.* network (the FreeBSD box).

Hope the above simplistic explanation solves your problem...

Tony