Category Archives: Carrier Ethernet
I ran into an interesting problem last week, and I found very little information on the internet about it. I will share it here, in the hope that it will help someone else.
Working with a newer product, I created a 10 Gig Link Aggregation configuration on my Cisco 7609 WS-X6708-10GE cards.
interface Port-channel1 description TA5000 40 Gig LAG switchport switchport trunk encapsulation dot1q switchport trunk allowed vlan 10-20 switchport mode trunk no ip address mls qos trust cos spanning-tree bpdufilter enable spanning-tree bpduguard enable lacp max-bundle 4 end
When I added the second link to the group, the Cisco kept putting the link into an alternate group!
Port-channel: Po1A ------------ Age of the Port-channel = 0d:00h:02m:47s Logical slot/port = 14/6 Number of ports = 1 Port state = Port-channel Ag-Inuse Protocol = LACP Ports in the Port-channel: Index Load Port EC state No of bits ------+------+------+------------------+----------- < 0 FF Te1/3 Active 8 Time since last port bundled: 0d:00h:02m:45s Te1/3
I searched the web for any indication of what the A meant on the end of the port-channel group, but I came up empty. All I knew was that my config looked good, and the Cisco would not add the second link into the group. The only thing I could find about this “alternate” group was, “if something on the other end doesn’t match exactly, the Cisco will declare the link in a new group”.
Armed with that little information, the search begins.
Doing a ‘show lacp neighbor detail’ gave me the information I needed to find the issue.
Partner Partner Partner Port System ID Port Number Age Flags Te1/3 00001,00a0.c8c8.3edd 0x3 0s FA LACP Partner Partner Partner Port Priority Oper Key Port State 65535 0x1 0x3F Port State Flags Decode: Activity: Timeout: Aggregation: Synchronization: Active Long Yes Yes Collecting: Distributing: Defaulted: Expired: Yes Yes No No Partner Partner Partner Port System ID Port Number Age Flags Te1/4 00001,00a0.c8c8.414d 0xD 0s FA
As you can see, the System ID’s for each link being reported in the LACP protocol do not match. Now, in this case, this is true, as the end device is in a multi-chassis LAG configuration. In order to work with the Cisco, the System ID’s must match. The Alcatel 7750 does not do this check.
Changing the System ID, allows the lag group to come up.
Port-channel: Po1 (Primary Aggregator) ------------ Age of the Port-channel = 9d:20h:10m:33s Logical slot/port = 14/5 Number of ports = 2 Port state = Port-channel Ag-Inuse Protocol = LACP Ports in the Port-channel: Index Load Port EC state No of bits ------+------+------+------------------+----------- 0 55 Te1/3 Active 4 1 AA Te1/4 Active 4 Time since last port bundled: 3d:17h:48m:54s Te1/4 Time since last port Un-bundled: 3d:18h:09m:43s Te1/3