How can I force communication over two links ?

[tironevi]

We currently have several layer 2 switch stacks with an uplink to two 6509s (Core 1 and Core 2). I am trying to load balance communication across the two links. How can this be accomplished taking into consideration the following scenario:

5 x 3750 (SmartStack) SMI Catalyst with Vlan 1 and Vlan 2 configured. Gi1/0/1 Uplinked to core 1 and gi2/0/1 uplinked to core 2.

2 x 6509, Vlan 1 and Vlan 2 does not trunk between the cores.

2 - MSFC2 with HSRP configured.

How can I configure load balancing across the two uplinks ? Can this be done without having to trunk Vlan 1 and Vlan 2 between the two cores ?

Regards,

VT

[Prashanth Krishnappa]

I do not fully understand your question. What do you mean by loadbalancing in your scenario? Since there is no physical loop in VLANs 1 and 2(since you say you are not trunking them between the cores), both gig1/0/1 and gig2/0/1 on the 3750 should be forwarding for VLAN 1&2. Can you give an example and elaborate a bit?

[tironevi]

I would like to force VLAN 1 communication only on one uplink and Vlan 2 communication only on the other

uplink. In the event of a link failure, both Vlans should be trunking through the same uplink.

Example:

Gi1/0/1 is configured to trunk Vlan 1 and Vlan 2, but as long as Gi2/0/1 is up, it should only trunk Vlan 1.

Gi2/0/1 is configured to trunk Vlan 1 and Vlan 2, but as long as Gi1/0/1 is up, it should only trunk Vlan 2.

The reason for this is that I have 5 x 3750-48 switches stacked. Currently all traffic is defaulting through Gi1/0/1 (Connected to core 1) except if I change the HSRP Active router for Vlan 2 to Core 2, which is connected to Gi2/0/1.

I was wondering if there was a way to force this type load balencing at layer 2 without having to trunk vlan 1 and vlan 2 between the cores.

Regards,

VT

[Prashanth Krishnappa]

For this, you will need to trunk between the Core's so that you have a physical loop and STP can block at one of the gig uplinks say if CORE1 is STP root for VLAN1 and CORE2 is the STP root for VLAN 2. There is no other way to accomplish what you want.

[tironevi]

That is what I thought. Thank you for clarifying it for me.

Regards,

VT