Fibre Channel (SAN)

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TAO
Contributor
Posts: 21
Registered: ‎11-23-2011
Accepted Solution

Two trunked ISLs between the same two switches

Hi,

 

Brocade 6520, FOS 7.3.1c

 

I've been tasked with migrating ISLs to a new DWDM service. I have a 2 x port trunked ISL between a 6520 switch at site A and a 6520 switch at site B (merged fabrics). The new DWDM links are above the 30 metre tolerance for links within the same trunk so I can't add the new links to the existing trunks and decommission the old ones. Could I instead:

 

1. Within a separate port gourp, create a new ISL trunk on the new service

2. Increase the link cost of the old ISL trunk to push the traffic across the new links

3. Decommission the old links

 

Thanks

Valued Contributor
Posts: 549
Registered: ‎03-20-2011

Re: Two trunked ISLs between the same two switches

What you say is actually one of the best ways to do it. Just don't forget that link cost is unidirectional, so you have to increase it on both ends.
Alternatively, you can try portdecom, but sometimes it doesn't work over the DWDM connections.
TAO
Contributor
Posts: 21
Registered: ‎11-23-2011

Re: Two trunked ISLs between the same two switches

Thanks very much for the reply Alexey, much appreciated.

I was concerned about how the switches would deal with the routing with two separate ISL trunks between the same switches but I guess FOS just handles it.

Is it possible to estimate when the frames will utilise the new trunked ISL once the cost has been increased on the old trunked ISL? Is it immediate, seconds, minutes, or perhaps longer?  

Valued Contributor
Posts: 549
Registered: ‎03-20-2011

Re: Two trunked ISLs between the same two switches

The frames will start using the new connection when routing tables will include it in the topology, it usually takes just a few seconds after it is established.
TAO
Contributor
Posts: 21
Registered: ‎11-23-2011

Re: Two trunked ISLs between the same two switches

Great, thanks Alexey

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