Category Archives: Carrier Ethernet

Carrier Ethernet

Cisco 7609 10 Gig Link Aggregation

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.

Cisco Config

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.

Partner Information

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
Advertisements