Static channel bonding / 2960g behaviour.

Unanswered Question
Nov 5th, 2009

Posted by: jagould2000 - CONCIERGE SOLUTIONS

Nov 4, 2009, 2:07pm PST

I have two 2960G switches that are trunked and connected to dual Foundry load balancers to provide an HA configuration.

I want to connect my servers dual network cards to the two switches for redundancy. Mysql configuration would be a lot simpler if I could have a single IP address for these two network cards.

I've tried link aggregation using LACP (ethertrunk) but it wont work because the 2960 doesnt support "cross-switch ethertrunk". (It would work fine if both cards went to the same switch).

The only thing I have left, other than two ip's, is to do static link aggregation. In static mode, the server monitors the link state of the interface and bonds them without communication to the switch (LACP). However, in this configuration, both cards show up with the same MAC (one on each switch).

Few questions I have about this configuration:

- I have no idea how the switches will behave in this config. Will it route traffic properly?

- The mac address table will have the servers mac in both the port its plugged into and the trunk port. Will it send all traffic to both cards? What will the server do - throw one away?

- Any other ideas of how I can get just one IP without LACP?

- Anyone actually tried static link aggregation in a production HA environment?

Any help would be greatly appreciated as I need to get this online asap and the mysql configuration is a mess with dual ip's.


Foundry 4G x2, Cisco 2960G x2, Apple Xserve 10.6.1

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Jerry Ye Thu, 11/05/2009 - 17:46

The 2960 is not the right choice with your configuration. You need at least the C3750 (stackable) for the dual cross stack LACP.



jagould2000 Thu, 11/05/2009 - 18:20

I understand (now) that the 3750 would have been a better choice for this application as it offers cross stack lacp. However, we've already made a considerable investment in the 2960, redundant power supplies, etc. based on a recommendation from a Cisco channel partner. Purchasing two 3750 isnt an option (though will certainly be the choice as we expand)

Any insight into how the 2960 will behave in a static bonding setup as I previously described?


Jerry Ye Thu, 11/05/2009 - 18:34

It will not work correctly since the MAC will show up on both switch like you said in your previous email. When you said static bonding, what do you mean?



jagould2000 Thu, 11/05/2009 - 19:05

Static mode vs lacp mode. it bonds the interfaces just like lacp, making them one mac address, except instead of looking for lacp messages to monitor the connections, it just looks for a physical link.

Is there any way to configure two ports on different switches to fail to each other? Link is up on one switch, it fails so it brings up link on the coresponding port on the other switch?

Jerry Ye Thu, 11/05/2009 - 19:33

Oh I see what you mean by static bonding (static port channel/port channel mode on). It is not possible to configure two ports on different switches to fail to each other on the 2960. You might want to explore your server to see does it support active/standby NIC configuration.




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