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New Member

Cisco MDS & ISL Merge

Hi all,

It has been a while sine I've done ISLs between two MDS switches.  Here is the question I have.

We have two sites A & B, the VSANs are as follows:

Site A: VSAN40, VSAN80, VSAN100

Site B: VSAN40, VSAN80, VSAN100

As soon as the FCIP tunnel was created, all of the VSANs tried to merge, but appeared as segmented. We don't want any VSANs to merge.  To my knowledge the only way to prevent the VSANs from merging is by making sure that all VSANs have unique VSAN IDs.  However, since we're using FCIP & IVR, I would have thought that only the VSAN that contains the FCIP interface would have tried to merge.  For example, the fcip interface is in VSAN100, I would have thought that only VSAN100 would have tried to merge and the rest of the VSANs would have remained untouched.  Trunking is disabled on for the fcip interface.

Our goal is to not merge the fabrics, but simply share some resources from site A to site B using FCIP and IVR.

Any thoughts?  Thanks in  advance.

New Member

Re: Cisco MDS & ISL Merge


Solution to your problem is using trunk allowed list configuration on ISAL interface.

When an ISL inteface comes up the default trunk allowed list configuration is to allow all VSANs. You can trim the trunk allowed list to manage the VSANs that can traverse an ISL.

Read more here :



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