I have googled/searched for this everywhere but haven't been able to find a solution. Forgive me if I leave something out but I will try to convey all relevant information. Hopefully someone can provide some insight and many thanks in advance.
I have three switches (A, B, and C) that are all running OSPF and LACP port channelling among themselves on a production network. Each port channel interface contains two physical interfaces and trunks a single vlan (so a vlan connecting each switch over a port channel). OSPF is running on each vlan interface.
Switch A - ME3600
Switch B - 3550
Switch C - 3560G
This is just a small part of a much larger topology. This part forms a triangle, if you will, where A is the source and C is the destination. A and C connect directly via a port channel and are OSPF neighbors. A and B connect directly via a port channel and are OSPF neighbors. B and C connect directly via a port channel and are OSPF neighbors. Currently, all traffic from A to C traverses B. I would like to load balance traffic sourced from A with a destination of C on the direct link and on the links through B. If all traffic is passed through B, traffic is evenly split on the two interfaces on the port channel. If all traffic is pushed onto the direct A-C link, traffic is evenly balanced on the two interfaces on that port channel. If OSPF load balancing is configured on the two vlans from A (so A-C and A-B), the traffic is divided to each port channel but only one port on each port channel is utilized while the other one passes nothing. So half of each port channel remains unused. The port channel on B-C continues to load balance, evenly splitting the traffic received from half of the port channel from A.
A and C port channel load balancing is configured for src-dst-ip. B is a 3550 and does not have this option, so it is set to src-mac.
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I suspect the issue you're seeing is both OSPF ECMP, using CEF (?), and Etherchanneling, using ip-src-dest, are effectively hashing into two paths, using similar attributes, so that might be why you're seeing only one port-channel link being used for traffic that's already been OSPF'ed ECMP.
To better understand the issue, you might read: http://www.cisco.com/c/en/us/support/docs/ip/express-forwarding-cef/116376-technote-cef-00.html
In your case, think of the routing split and the Etherchannel split, as if there were two CEF routers in series.
What might help in your case is to use a different Etherchannel hashing algorithm, perhaps just ip-src or ip-dest.
Thanks. It would seem this configuration is passing traffic exactly the way it's supposed to, it's just not what I'm trying to do. I will try to wrap my head around the polarization problem. It seems the ME-3600 doesn't have mls configuration options (image file is me360x-universalk9-mz.122-52.EY3.bin), so I might be somewhat limited in that area. I did try some different port channel load balancing options but the only thing I could get to happen was moving traffic to the other half of the port channel.
This is more FYI. 10.82.4.0/24 is a subnet on switch C. The path to it is split across vlans 10 and 11 but once it hits the port channel interfaces only one side of each is chosen. I'd like to avoid creating more vlan interfaces but right now that appears to be the only way to load balance equally across the four interfaces out of switch A.
ME3600#sh ip route 10.82.4.0
Routing entry for 10.82.4.0/24
Known via "ospf 1", distance 110, metric 154, type extern 1
Last update from x.x.x.153 on Vlan10, 01:20:46 ago
Routing Descriptor Blocks:
x.x.x.153, from 10.82.15.1, 01:20:46 ago, via Vlan10
Route metric is 154, traffic share count is 1
* x.x.x.135, from 10.82.15.1, 01:20:46 ago, via Vlan11
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