Following up on this. Does the 3560 support etherchannel hash on src-
dst-mac and src-dst-ip? This should change up the hash between CEF and
etherchannel and prevent a polarization like effect.
-Ben
On Nov 11, 2010, at 4:58 PM, Benjamin Lovell wrote:
This really just shot in the dark but you have CEF hash for ECMP and
then etherchannel hash for link selection. I wonder if it's a weird
example of polarization such that because CEF hash decided left now
all traffic subject to etherchannel hash for that port-channel will
resolve to one link.
I don't know if this is true of how the CEF versus etherchannel
hashing works but it fits your results.
-Ben
On Nov 10, 2010, at 12:34 PM, Brandon Ewing wrote:
I've got a weird problem that I hope someone can shed some light
on. We
have multiple 3560G's deployed currently, each utilizing 4 SFP's
for uplink.
The switches are configured with 2 L2 port-channels, with a
different SVI in
each port-channel pointing to our upstream router. IE:
g0/49 + g0/51 to core A, carries Vlan 100
g0/50 + g0/52 to core B, carries Vlan 200
Group Port-channel Protocol Ports
------+-------------+-----------
+-----------------------------------------------
4 Po4(SU) LACP Gi0/49(P) Gi0/51(P)
5 Po5(SU) LACP Gi0/50(P) Gi0/52(P)
We have two default routes, pointing out the above vlans:
switch#show ip cef 0.0.0.0 0.0.0.0
0.0.0.0/0
nexthop 10.10.1.241 Vlan200
nexthop 10.10.1.245 Vlan100
The etherchannel load-balancing method is set to src-dst-ip:
switch#show etherc load-balance
EtherChannel Load-Balancing Configuration:
src-dst-ip
EtherChannel Load-Balancing Addresses Used Per-Protocol:
Non-IP: Source XOR Destination MAC address
IPv4: Source XOR Destination IP address
IPv6: Source XOR Destination IP address
However, we are not seeing an even distribution of traffic among
the 4
ports -- each L2 etherchannel is trasmitting on only one port:
switch#show control util
Port Receive Utilization Transmit Utilization
Gi0/49 1 55
Gi0/50 6 0
Gi0/51 1 0
Gi0/52 12 57
Examination of flowstats from the core on the uplink interfaces
shows a good
mix of src/dst IPs -- so why am I getting the polarization?
Additionally, examining a test flow with the command line shows
that it
SHOULD be working, but it's not:
switch#show ip cef exact-route 172.16.79.186 192.168.42.183
172.16.79.186 -> 192.168.42.183 => IP adj out of Vlan100, addr
10.10.1.245
switch#test etherchannel load-balance interface po4 ip
172.16.79.186 192.168.42.183
Would select Gi0/51 of Po4
However, g0/51 has no traffic on it, and hasn't for some time. Can
anyone
provide some clue? This is occuring on multiple switches, and all
switches
are running 12.2(50)SE1 ip services
--
Brandon Ewing ([email protected]
)
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