2 messages in net.nether.puck.cisco-nsp[c-nsp] 3750 CEF and equal cost multi...
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Matt BazanJan 6, 2005 12:03 pm 
Oliver Boehmer (oboehmer)Jan 6, 2005 12:20 pm 
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Subject:[c-nsp] 3750 CEF and equal cost multihomingActions...
From:Oliver Boehmer (oboehmer) (oboe@cisco.com)
Date:Jan 6, 2005 12:20:08 pm
List:net.nether.puck.cisco-nsp

Matt Bazan <> wrote on Thursday, January 06, 2005 6:04 PM:

Have a mystery I'd like to solve: On one of my 3750 switches I've setup two static routes with equal metrics (on two separate routed ports) via their respected interfaces (gi1/0/19, gi1/0/21) to a /27 network. So, I've got two routes in my routing table that look like this:

XX.XXX.XXX.XXX/27 is directly connected, GigabitEthernet1/0/19 is directly connected, GigabitEthernet1/0/21

You don't want this. Please always specify a next-hop along with the interface, i.e.

ip route XX.XXX.XXX.XXX 255.255.255.224 GigabitEthernet1/0/19 a.b.c.d ip route XX.XXX.XXX.XXX 255.255.255.224 GigabitEthernet1/0/19 e.f.g.h

where a.b.c.d and e.f.g.h are the respective next-hop addresses.

[...]

Is it possible to have the router only use the interface that has the arp entry mapped to it?

No. If you set-up routing like you did, you end up arp'ing for every destination address in this network range. This can create quite a high ARP activity which you want to avoid. When you specify the next-hop, the router only needs to arp once, and you'll be set.

oli