Anonymous
Posts: 0

# Long distance ISL between 5100 and 5300 switches

We have 2 sites that where we want to connect the SAN fabric via ISL trunk. On the first site we have 5100 switches and on the other sites we have 5300 switches. All switches have Extended Fabric and Trunking licensees.

Between the two sites we have two dark fiber connections that are multiplexed. The first of the fiber connection is approx. 47 km and the other is approx. 58 km. We have 8 Gb wave length SFPs for 80 km and two assigned wavelengths on each fiber.

How should we best connect these two sites?

Our first plan was to use one wavelength on each fiber to connect each fabric so that both fabrics would still be fully operative if one of the fiber connections was broken. But we was then told that different length on the connection in a trunk could cause problems. So then we guess that each fabric should use two wave length on the same fibre for connection?

We was also told that all ports within a trunk should be within the same 16 port block. Because of the length in this scenario there are not enough buffer credits to achieve this. The 5300 switch have 292 buffer credits pr. 16 ports and the 5100 switch have 1692 credits for the whole switch. I have found out that my 58 km link needs approx. 240 buffer credits, and then I can't have two link within the same 16 port block.

Is there anybody that have a good design proposal for us in this case?

Anonymous
Posts: 0

## Re: Long distance ISL between 5100 and 5300 switches

When trunking you need all the ISL in the trunk to be of the same lenght.

With 47 and 58 KM the difference is far to great, what you could do (maybe impractical) is the have an 11KM spool of fiber somewere to make both fiber runs 58KM. PS a difference with in 30 meter range gives the best performance.

Trunkports do need to be on the same portgroup.

How did you do your buffercredit calculations and against which speeds?

Reason for me asking is that perhaps in your scenario a lower speed setting would be sufficient bandwith- and buffercreditwise .