Isl Connectivity between DS 5100 and DS5300 switches

You also need a trunking license, but that's out of scope in your question

make sure the domain ids are different on all switches and that's about it. As soon as you connect 1 port of each switch together a trunk will form and the fabrics will merge. This will take only a moment. As soon as the fabric is stable again (in the GUI it now shows 2 switches instead of 1 and they're green) enable the 2nd ports on both switches and the trunk will then have 2 ISL's.

Physically you need to know how much power the SFP's have for transmitting and receiving and the dampening factor of all components inbetween. If the receiver part of the SFP on the other end receives too much power (light), it can break down (burn), but I think at 80km you are fine, but still I'd do the math to be sure. If the transmit power is too high and the components inbetween aren't damping this light enough you need to put an attenuator (extra dB damping) on that fiber. You don't need to do this on both sides, I'd only do it on the reveiving end, but since each SFP is receiving and sending, you should do it on both receiving ends of each fiber.

Everything RRR said, but I'm not sure if I'm misreading, or misunderstanding so I'll try to clarify one point.

It looks like you intend to have two 5300 switches at the production end and they will NOT be connected to each other. You will also have two 5100s at the DR site and THEY will not be connected to each other. You are planning on connecting 1 ISL from each 5300 to a matching 5100. This will make two fabrics that each span from the Prod site to the DR site. This is how I interpret your initial note.

If this is correct I would strongly suggest you double up the ISLs for each fabric. If you only have 1 ISL per fabric you will invariably run into situations where you are segmenting one fabric or the other. With two ISLs you can significantly reduce the number of times this will occur. Personally I would always argue against single ISL configurations between switches unless you have accounted for redundancy another way (e.g. in a dual core edge topology you might have a single ISL to each core from each edge switch, but you still have redundancy).

In RRR's response he alludes to the second ISL being there, but I don't see anything in your initial post that inidicates it is planned. That being said I can understand that you don't want to use more dark fiber than you have to, but if this were my environment I would say "We HAVE to!"

Thanks Allen and RRR. Have kept in mind the suggestions made.

Coming back to your reply Allen as you have mention in your post in the second para, I intend to setit up in th fashion I mentioned as you have understood.

One isl from 5300(PROD) to 5100(DR) and another ISL similary from the 5300(PROD) to 5100(DR) switches. As you have understood correctly there will be no connection between the 5300's and the 5100's invidually. This will be connected entirely over dark fibre having a latency 0.025 msec between the two sites.

Since the dark fibre has already been laid, I plan:

-To connect the switches to each site (Prod and DR)  respectively,

-Install the ELW SFP's on the ports on the switch and then install the extended long wave license on each of the switches and then

-Connect the fibre cables at the Production and DR site to check for ISL formation and

-Issuing the command portcfglongdistance 0  LD 1 65 for the isl over long distance.

Hope this plan looks good. Your suggestions are welcome to make this plan better.

Hope all goes well with this plan Aj007.

Again I would stress that best practices would indicate two ISLs for each fabric, but as long as you are aware of the potential impact of fabric segmentation from events like cable problems, SFP failures, etc. (and document it so someone can sign off on accepting the risk vs. cost) then I think you are all set.

You don't need to change Domain Id's when adding switches into fabric. Switch with Lowest WWN wins election and becomes primary switch.

if you want a specific switch to be primary then you need to hard set the switch as primary by typing fabricprincipal command on the switch.

Domain Id's don't play a role in mergic zones the switch automatically resolves any domain id conflicts. best way is to set the switches to use insistend domain ids that would auto-select domain id when 2 switches are merged in the fabric.

Thanks AshG, but I can't entirely agree with some of your points. Things may have changed since the last time I researched this, but there used to be a whole lot more go into election of the Primary switch than just WWN. There were things like firmware versions, switch model, and various settings that influenced the decision before WWN was considered.

That's not really the part I disagree with though. Your statement about Domain ID's not playing a role could be "right" under a very specific set of circumstances. Unfortunately under a different specific set of circumstances it is completely wrong. If you set Insistent Domain IDs on two switches and set them to select the same Domain ID you WILL NOT be able to ISL them together. You will get a link, but it will not be an ISL. It will show as a segmented fabric and you will not be able to have the zone sets merge. Best practice would be to ensure that the Domain IDs are different before attempting to ISL to avoid issues. No matter what the setting for insistent Domain ID, if the IDs conflict you will have to take an outage on one of the switches to reset the ID in order to merge.

I'm hope you don't take this as argumentative, but I want to make sure that other new users get the right info so they don't get themselves into trouble due to a misunderstanding.