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New Member

Gigabit EtherChannel across Supervisor III in Cat5500

I have two sites, one with a Cat5509 and the other with a Cat5500. Both devices have dual supervisor IIIs with the 2-port Gigabit module on each supervisor.

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I want to ask whether running Gigabit Etherchannel will work if the channel members are Gigabit ports on a different physical supervisor.

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In other words, the gig port in the active sup3 in 5500 and the gig port in the standby sup3 can be added to a single channel group. I am aware that new code allows the use of the gig ports on a standby sup3, but I do not know whether the Gigabit Etherchannel feature will work across separate sup3 ports. This will be identically configured at the other site as well (if it works !!!)

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The idea behind this is to create a fully redundant link between the two Cat5k switches, in the event that a sup3 should fail at either end.......the etherchannel group will still operate over the standby sup3 because they are configured in channel groups.

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Any ideas ??

2 REPLIES
Bronze

Re: Gigabit EtherChannel across Supervisor III in Cat5500

From everything I read on CCO it looks like they have to be on the same Sup. Has anyone out there tested this?

New Member

Re: Gigabit EtherChannel across Supervisor III in Cat5500

I feel pretty sure that you can only set up channels between ports on the same blade/module.

I've set up similar core links between Cat5500's with Sup3G's. In my case, I ended up with parallel links and allow STP to block one. The failover time is actually pretty good, a couple seconds at most.

By the way, if you're concerned about losing half the capacity by having one link blocked, I was concerned about the same thing. Evidentally, port channeling only yields 60-70% bandwidth increase, according to some reading I've done. It seems that the channel maintenance between the switches takes up quite alot of bandwidth, so from what I can gather, you'd be going to 1.6 1.8 GB usable capacity. I guess what that did for me is put my mind at ease a bit to know that I wasn't losing *half* the bandwidth by seeing that port stay in blocking mode.

The Cat5500 only has a 3.2GB backplane, which may also be of comfort.

Perhaps someone out there can clarify the port channeling capacities in general, and specifically with the Cat5500 series?

If I'm wrong on any of this, let me know!!!

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