Two NIC's connected to same subnet: routing question

Xin LI delphij at frontfree.net
Tue Feb 1 10:13:21 PST 2005


Dear folks,

I think I got confused with the routing problem we will have when at
least two NIC's are connected into the same subnet.

The scenario:
em0: 192.168.0.1/24
em1: 192.168.0.2/24

We can't simply configure like this, since 192.168.0.0/24 network route
exists as soon as either em0 or em1 is up.  A workaround for this is
that we assign 192.168.0.2/32 for em1, but that has another issue that
all traffics will go through em0 for "outgoing", say, outside the
current network.

A google of the issue has indicated that the "Move ARP out of routing
table" work done last April should have resolved this, as "With this
change it is possible to have more than one interface in the same IP
subnet and layer 2 broadcast domain.".  However, what I have found from
our mailing list archive says only to assign /32 IP address, or remove
routing item from route table, which is essentially identical to the /32
solution.

So is there any way to utilize the both NIC's?  I think I have been
confused :-(

Cheers,
-- 
Xin LI <delphij delphij net>  http://www.delphij.net/
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