Re: two ethernet cards
On Tuesday 28 May 2002 23:44, kbdlock@attbi.com wrote:
> eth0 Link encap:Ethernet HWaddr 00:A0:CC:53:66:08
> inet addr:192.168.1.1 Bcast:192.168.1.255
>
> eth1 Link encap:Ethernet HWaddr 00:A0:CC:61:E9:65
> inet addr:192.168.1.20 Bcast:192.168.1.255
>
> No major problem here except that eth1 appears to be
> getting no traffic.
>
> Someone told me that it was a routing issue, but I have
> no idea if that's true or not. I really don't know what
> the problem here is, least of all how to fix it.
They are correct -- this is a routing issue. This came up on the
debian-user list about a month ago (search the list archives). There
was a long discussion about why this happens.
The short version is this: the kernel will not use two NICs if they
are on the same physical network (or if the kernel *thinks* they're on
the same physical network).
Even though you've given a different IP address to each card, both of
your cards are on the 192.168.1.* network, so the kernel just uses one
of them and ignores the other. In order to get both working, you'll
have to assign a different network to one of them. Examples include:
eth0: 192.168.1.*
eth1: 192.168.2.*
eth0: 192.168.1.*
eth1: 10.0.0.*
Basically, if eth0 has to be 192.168.1.*, then the other card can
*not* start with the same three octets. Pick any other numbers and
you'll be fine.
Again, the reason why the kernel does this is rooted in how ethernet
and IP networks are designed. Search the archives for more info on
why this happens and why you can't change this behavior.
Hope that helps,
Jason
--
Jason Healy
http://www.logn.net/
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