2014年1月9日星期四

Connecting 2x stacked Cisco 3750 to 1x Cisco 2950

We have 2x Cisco WS-C3750X-24T-L   switches that have been partitioned into various VLANs. These switches are stacked, and the VLAN partitioning is symmetrical on both switches - that is ports x-y on switch 1 are in the same VLAN as the corresponding ports x-y in switch 2. This enables us to have redundancy with the networking of our servers as NIC1 of each machine is plugged into switch 1 and NIC2 is plugged into switch 2. Fairly standard stuff, I'd imagine...

We have some devices (managment NICs etc) that need to be in a particular VLAN (our management VLAN in this case). As these are inherently "single NIC" connections, and also because they are not used day-in-day-out (just on the odd occasion when we need to remotely manage the servers), it makes sense to connect these to another, cheaper, slower switch (enter the 2950) - so they don't use up valuable gigabit ports on the 3750s.

We don't want to lose the redundancy, however - even though these aren't connections that will be used frequently, we still want them to be as available as possible.

I'd like to be able to connect the 1x 2950 to BOTH of the 3750s in such a way that devices in the 2950 would be still available on the network if either of 3750s lost power.

My thinking is having a crossover cable from a port in the management VLAN on each 3750 attached to a port in the 2950, and configured to be trunked or aggregated in some way (I'd imagine there'd need to be special config to prevent routing loops). I have attached an image of what I imagine this setup would look like.

Please could someone let me know if this is possible, and if it is, also provide the relevant config required for each  WS-C3750X-24T-S    switch (only pertinent sections - port channels, interfaces)

If they're in the same subnet, they're in the same VLAN. So there's no need for a trunk.


You can connect the switches and let spanning-tree deal with the redundant link or do as Arnie says and channel the links. Since it's a low-use situation, there's not much difference as far as functionality goes.

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