From: "Steven N. Fettig" <[EMAIL PROTECTED]>
To: Travis Troyer <[EMAIL PROTECTED]>, FreeBSD - questions <[EMAIL PROTECTED]>
Subject: Re: 3 Nics - Dual (Tripe) Homed Host
Date: Mon, 10 May 2004 09:55:46 -0500


Travis Troyer wrote:

I have a FreeBSD system that acts as a NAT Gateway, currently providing on LAN with access to the Internet. I have added a third NIC, connected to a second LAN. The second LAN does not need internet access, but I would like it to be able to communicate with the first LAN. I have tried reading various sources, but have not found anything dealing with this situation. I would appreciate any help. Below is a diagram of my current setup and the output of ifconfig.

                            Internet
                                |
                [ xl0: DHCP assigned ]
                           Router
                            |      |
            [ xl1: 10.0.0.1]  [ xl3: 192.168.1.10]
        10.0.0.0/24 LAN  192.168.1.0/24 LAN

Output of ifconfig:
xl0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
       options=8<VLAN_MTU>
       inet 24.33.126.252 netmask 0xffffff00 broadcast 255.255.255.255
       ether 00:60:97:74:35:b0
       media: Ethernet autoselect (10baseT/UTP)
       status: active
xl1: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
       options=b<RXCSUM,TXCSUM,VLAN_MTU>
       inet 10.0.0.1 netmask 0xffffff00 broadcast 10.0.0.255
       ether 00:01:02:37:93:eb
       media: Ethernet autoselect (100baseTX <full-duplex>)
       status: active
xl2: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
       options=b<RXCSUM,TXCSUM,VLAN_MTU>
       inet 192.168.1.10 netmask 0xffffff00 broadcast 192.168.1.255
       ether 00:01:02:cc:63:d2
       media: Ethernet autoselect (100baseTX <full-duplex>)
       status: active
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
       inet 127.0.0.1 netmask 0xff000000

Travis,

Although I have been dealing with routing for years, I can't claim I really understand it well, so my advice may not be so intelligent, but here's a stab at it anyway:
I think what you want to do is to bridge both LAN's. You need to tell your gateway that in order to get to 10.0.0.0/24 from 192.168.1.0/24, you need to tell the routing tables that the route to 10.0.0.0/24 is via xl1 and vice versa.


route add 10.0.0.0/24 -interface xl1

and vice versa:

route add 192.168.1.0/24 -interface xl2

In the handbook, it says (http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/network-bridging.html):
<--begin quote-->
19.5.4 Enabling the Bridge


Add the line:
net.link.ether.bridge=1


to /etc/sysctl.conf to enable the bridge at runtime, and the line: net.link.ether.bridge_cfg=if1,if2


to enable bridging on the specified interfaces (replace if1 and if2 with the names of your two network interfaces). If you want the bridged packets to be filtered by ipfw(8), you should add:
net.link.ether.bridge_ipfw=1



as well.


For FreeBSD 5.2-RELEASE and later, use instead the following lines:
net.link.ether.bridge.enable=1
net.link.ether.bridge.config=if1,if2
net.link.ether.bridge.ipfw=1
<--end quote-->

I am not sure if this will work, though, because I'm not sure what effect (if any) it would have on the NAT from the 192.168.1.0/24 network. You might want to first try this approach while NAT and the firewall are turned off. I have a similar situation that I want to test, so I'd be curious if you succeed and how.

Steve Fettig


Steve,


Thank you for your suggestion, however, I gave that a try, and really wasn't getting anywhere. For the sake of not angering the roommates too much by having to disable NAT, I tried every option but that. In my research I found out about Virtual Hosts, or IP aliasing, and, since there were only two machines on the 10.0.0.0 network that needed to access machines on the 192.168.1.0 network, and they were both running FreeBSD, I simply gave each machine a second IP on the 192.168.1.0 network, and everything is working fine. In case you're interested, I used this bit of information:

http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/configtuning-virtual-hosts.html

I'm not sure if you were aware of aliasing, as I was not, or if this fits your situation as well as it did mine. I'm curious now as to whether or not my gateway/router machine could still provide connectivity between the two networks, via the virtual hosted interface, for clients on both LANs. Though my setup suites me now, I may give that a try.

Regards,

Travis Troyer

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