topic Re: using Linux as a bridge and firewall in Operating System - Linux

using Linux as a bridge and firewall

K.C. Chan — Wed, 12 Jun 2002 02:23:43 GMT

All,
I've tried setting up RH 7.2 as a Bridge and Firewall. I've re-compiled the kernel 2.4.18 to include bridging. Put eth0 and eth1 in promiscius mode and enable bridging via "brcfg -ena"
but it's still not working bec. I am only able to ping one side of the network not the other.

Here's what I want to do, I have eth0=63.x.x.x.133 and eth1 as 63.x.x.x.134. eth0 has a route to the default router and eth1 is connected to a hub/switch (the protected side of the network; this is only a test, as soon as I get this to work with iptables it's going in btw the router and the switch). How do I make eth0 and eth1 pass network traffic to each other so that I can ping all servers on eth0 side and all servers on eth1 side?

Re: using Linux as a bridge and firewall

U.SivaKumar_2 — Wed, 12 Jun 2002 04:49:50 GMT

Hi,
Have configured in such a way that only non-routable protocols to be bridged and IP should
be routed ?.
regards,
U.SivaKumar

Re: using Linux as a bridge and firewall

K.C. Chan — Wed, 12 Jun 2002 13:09:59 GMT

Yes, I've tried routing but it onl works on 1 interface of the NIC; since both Nic have the same network (63.78.100.0 I can only seem to route out one interface). e.g:
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
63.78.100.0 0.0.0.0 255.255.255.0 U 40 0 0 eth1
63.78.100.0 0.0.0.0 255.255.255.0 U 40 0 0 eth1
127.0.0.0 0.0.0.0 255.0.0.0 U 40 0 0 lo
0.0.0.0 63.78.100.1 0.0.0.0 UG 40 0 0 esome_pc_on_eth0_sideth0

For some reason I can ping with "ping -I eth0 some_pc_on_eth0_side", it works and vice versa with "ping -I eth1 some_pc_on_eth0_side". But if I ping with the "-I" option, it doesn't work. I know if I tried to ping (w/o the -I option) the router which in on eth0 side, I can't reach it because both route for 63.78.100.0 points to eth1 side. I've tried adding 63.78.100.0 for eth0 but it doesn't work. This is why I think a bridge might work. Any idea on how should I approach this? Should I use bridging or Routing. If so please shed some light onto this. Thanks.

Re: using Linux as a bridge and firewall

K.C. Chan — Wed, 12 Jun 2002 20:17:19 GMT

All, I got this to work. Basically I was missing a patch for kernel 2.4.18; specificallly the bridging patch.