How to connect Nexus 3000 switch to Cisco 3750 IOS switch which is in stack.

[yog19812003]

Hi, 

We have purchased two new Nexus 3064. We are planning to upgrade the network backbone from 1 Gig to 10 Gig. Current setup - the ESXi servers are connecting to existing WS-C3750X-48T-S x 5nos in stack.

We are planning to connect the servers -> Nexus (vPC) and Nexus to existing 3750. We'll be installing 10 Gig Network Modules in the existing switch to have 10 Gig uplinks. 

My question is how we should connect Nexus 3000 to 3750. We have got two 10 Gig ports on each module. So my thinking is like one port from 3750 will connect to first Nexus and other will go second one. And we'll have vPC at L2 trunks. The same will be repeated to other switches.

Please let me know your suggestion.

[Steve Fuller]

Hi,

I think the choice of cross stack EtherChannel on the Catalyst 3750 to connect to vPC on the Nexus 3000 seems like a reasonable approach.

I'm not sure how many links you intend to use, but it sounds like you have two 10GE links from each physical switch of the stack. If that's the case and you intend to connect 10 * 10GE links in the port-channel, remember that while you can configure up to 16 ports as members of a port-channel, only eight of the ports are in active mode. There will be two ports in standby mode.

The other point to note is that the Nexus supports IEEE 802.3ad Link Aggregation Control Protocol (LACP), whereas the Calalyst will support LACP and the Cisco proprietary Port Aggregation Protocol (PAgP). This shouldn't be a problem as long as you configure both the Nexus and Catalyst to use an LACP (channel-group <group> mode active) or static (channel-group <group> mode on) aggregate. I'd recommend using LACP.

Regards