Issue with Equal Cost Static Default Routes

Unanswered Question
Apr 9th, 2009

Question:

I'm trying to troubleshoot an issue with equal cost static default routes. Here is the configuration of the 3560:

..

interface FastEthernet0/1

no switchport

ip address 8.8.8.1 255.255.255.0

!

interface FastEthernet0/2

no switchport

ip address 9.9.9.1 255.255.255.0

!

interface Vlan1

ip address 50.50.50.1 255.255.255.0

!

....

!

ip route 0.0.0.0 0.0.0.0 8.8.8.2

ip route 0.0.0.0 0.0.0.0 9.9.9.2

"show ip route" output

Gateway of last resort is 9.9.9.2 to network 0.0.0.0

50.0.0.0/24 is subnetted, 1 subnets

C 50.50.50.0 is directly connected, Vlan1

8.0.0.0/24 is subnetted, 1 subnets

C 8.8.8.0 is directly connected, FastEthernet0/1

9.0.0.0/24 is subnetted, 1 subnets

C 9.9.9.0 is directly connected, FastEthernet0/2

S* 0.0.0.0/0 [1/0] via 9.9.9.2

[1/0] via 8.8.8.2

I'm pinging 4 different IPs out in the cloud with two equal cost default routes configured on a 3560. The IPs that I'm trying to ping are 1.1.1.1, 2.2.2.2, 3.3.3.3, and 4.4.4.4 - sourcing from 50.50.50.50. However, when I ping all four IP simutaneously it only egresses the 8.8.8.0 gateway.

I've used the "show ip cef exact-route" output. Which looks like it should distribute the load based on destination.

Switch#sh ip cef exact-route 50.50.50.1 1.1.1.1

50.50.50.1 -> 1.1.1.1 => IP adj out of FastEthernet0/1, addr 8.8.8.2

Switch#sh ip cef exact-route 50.50.50.1 2.2.2.2

50.50.50.1 -> 2.2.2.2 => IP adj out of FastEthernet0/1, addr 8.8.8.2

Switch#sh ip cef exact-route 50.50.50.1 3.3.3.3

50.50.50.1 -> 3.3.3.3 => IP adj out of FastEthernet0/2, addr 9.9.9.2

Switch#sh ip cef exact-route 50.50.50.1 4.4.4.4

50.50.50.1 -> 4.4.4.4 => IP adj out of FastEthernet0/1, addr 8.8.8.2

"show ip cef" output

Switch#sh ip cef

Prefix Next Hop Interface

0.0.0.0/0 8.8.8.2 FastEthernet0/1

9.9.9.2 FastEthernet0/2

"traceroute" output

Tracing the route to 1.1.1.1

1 8.8.8.2 0 msec

9.9.9.2 0 msec

8.8.8.2 0 msec

Any thoughts to why it only goes out one gateway and not both based on the cef table?

I have this problem too.
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Edison Ortiz Thu, 04/09/2009 - 07:12

Denny,

Your equal cost static routing is working but the result is not showing as expected since you are doing it from the switch itself.

Best to setup a couple of clients in Vlan1 targeting different destinations to see the full effect.

__

Edison.

denny.lee Thu, 04/09/2009 - 07:17

I've tried this from several different hosts connected to the switch with the same results.

Edison Ortiz Thu, 04/09/2009 - 08:14

From the traceroute you've shown, it's displaying the load-balancing taking effect.

__

Edison.

denny.lee Thu, 04/09/2009 - 08:40

Yeah. That was the output from the switch and how packets should be traversing to the respective destinations. Testing is a different story altogether. Once I have multiple hosts connected to the switch each simultaneously pinging all the hosts mentioned - all traffic leaves one interface.

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