3 NIC's in 1 PC - tcp mess up.

Posted on 2001-08-21
Last Modified: 2013-12-23

I have a FreeBSD-4.3 stable with 3 network cards :

1 x 100mbs connected via cross-over to another machine (which works fine) (rl0)

2 x 10mbs - the other is connected to an ADSL-box (ed0) (which also works fine) and the other is going to a 10mb HUB (xl0) - which also works physically. Link speedlight etc lights are correct - so that side is fine. BUT :

I've defined all the interfaces in rc.conf, given them IP's and they are all seen in ifconfig -au. With correct values.

Now I have a routing rule (ipfw) which states :
- divert 8668 ip from any to any via ed0
- allow ip from any to any

Okay - the link works fine between the 100mb and the other 10mb going to the ADSL, but the one going to the hub is not responding to ping.

The ed0 is, the xl0 is .1.2
I think the reason is that everything is diverted to ed0 before it searches for any other local interfaces or something similar... What can be done in order to get the 1.2 interface to respond?


Question by:acidia
  • 2
LVL 40

Accepted Solution

jlevie earned 150 total points
ID: 6424248
The firewall rules could be the problem, but it could also be that the third NIC is sharing an IRQ with something else. That will prevent it from seeing an inbound ping as the driver won't get the interrupt. And you can pretty easily find out if the firewall rules are diverting everything to to edo with tcpdump. Just look at all of the traffic and see if the system even sees the inbound ping.

If, as I suspect, it is an IRQ conflict problem you'll have to find some way to free up an IRQ for use by the third NIC. Depending on what you have on the box and what IRQ's the NIC's can use, you may be able to disable one or more devices in the BIOS (like one or more COM ports, USB, PS/2 mouse, parallel port, etc). Also make sure that PnP mode is disabled in the BIOS (if your BIOS allows).

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