Domain ID for new switches

Question

Hi,

We have two cisco 9513's in each fabric. I need to spread a vsan across both the switches. By going through the cisco documentation, my understanding has been that domian id's are given at the vsan level in cisco switches.

Now, here are my questions. I will be connecting isl's in the default vsan 1.

1.once i activate the isl's will i be seeing both switches connected??

2.can i now configure a new vsan with ports from both the switches, or should i create the vsans first on both the switches and add the vsan to the isl??

3.what are the domain id requirements, i mean say should the switch 1 have a lower domain id then switch 2??? if so, how do i configure the domain id.

Thanks,
Karan

RRR · Accepted Answer

It's a best practice to put the E ports themselves in VSAN 1 and allow the VSAN which holds the F ports over that ISL. I wouldn't allow VSAN 1 over that ISL. You don't need a transit VSAN if your switches are local. If your distances are dependant on external influences, for example a provider of your dark fiber between cities, I'd use a transit VSAN to eliminate unwanted RSCN's when the link goes down. In that case you would use for example VSAN 10 on 1 site, VSAN 20 on the other site and a transit VSAN 30 inbetween for Inter VSAN Routing (IVR) use.

So if your switches are local, simply allow the VSAN on the ISL and make sure that VSAN is present on each side of the ISL.

RRR · Answer

We have two cisco 9513's in each fabric. I need to spread a vsan across both the switches. By going through the cisco documentation, my understanding has been that domian id's are given at the vsan level in cisco switches.

True. So in fact each physical switch can have more domain ids: 1 for each VSAN.

Now, here are my questions. I will be connecting isl's in the default vsan 1.

You mean you'll be putting the E ports in VSAN 1 ? That's a good thought.

1.once i activate the isl's will i be seeing both switches connected??

Yes, but you'll need a VSAN to share accross both switches. So for example: if you have VSAN 10 which needs to be on both switches, create VSAN 10 on both switches and allow VSAN 10 on the ISL / portchannel.

2.can i now configure a new vsan with ports from both the switches, or should i create the vsans first on both the switches and add the vsan to the isl??

Create on both switches first and then start putting ports in that new VSAN

3.what are the domain id requirements, i mean say should the switch 1 have a lower domain id then switch 2??? if so, how do i configure the domain id.

No real requirements, then only need to be different. However, if you need a certain switch in a certain VSAN to be principal, you should lower the domain priority of that switch in that VSAN. By default it's 128 and if 2 switches merge and domain priorities are the same 1 will be elected as the principal. I prefer to control that myself and I would assign my main switch with a lower number as being the higher priority (Cisco logic: the lower the domain prio, the higher in the hierarchy this switch will be).
How ? Click on the VSAN you'd want to change domain priorities of and look in the upper right side of your fabric manager window. I don't exactly know what this tab is called (I don't have a Cisco MDS nearby to try), but you'll find it.

If I understand correctly you have 4 switches: 2 in each fabric ? And you're not going to interconnect both fabrics, right ?

karan2 · Answer

Thanks for the reply Rob. Just one more question.

Since i will be putting the E ports in VSAN 1 on both the switches, should not both the switches be connected. I mean why do we need to create another VSAN for the ISL's (like VSAN 10)???

Ofcourse i will be adding the productions VSAN's to the port channel, did you mean VSAN 10 as a production VSAN??

Yes, we have four switches, two in each fabric for redundancy.

Thanks,
Karan

karan2 · Answer

Thanks a lot for the reply Rob.Karan

RRR · Answer

You're welcome

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Domain ID for new switches

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