VLAN Routing


VLAN Routing


I have a HP ProCurve 5412 as my core switch. I have about 10 VLANs working fine on it, with the 5412 doing the routing between the VLANs.

I have a 3COM 3870 switch on the edge. I have an Exchange server plugged into this switch on VLAN 100.

My issue is that users on VLAN 1, 20, 30 etc that are on this 3870 switch must go through the 5412 to talk with the Exchange server. The default gateway for each VLAN resides on the 5412. I really want to keep the traffic local in this 3870 switch without having to go to the core and back.

How would I set this up? I would assume I would need to enable Layer3 routing on the 3870?  Does VLAN 100 have a different subnet/default gateway on each switch?  What's the best practice in a situation like this?

I just need some pointers so I can get this working in a test lab.



Esteemed Contributor

Re: VLAN Routing

Yes, you would need to enable routing on the 3870 to keep traffic local to the switch.  The 3870 would need its own IP address on VLAN 100 that is different to the 5412.  You would also need to set the workstations & servers on that switch to use the 3870's address as their default gateway, otherwise any traffic for other VLANs would go via the 5412 regardless.

I would not run two different subnets on the same VLAN, simply because it causes confusion.  I think it would also be confusing to have two different switches doing the routing between the same VLANs unless you implemented some sort of dynamic routing like OSPF (or even RIP) so that each of the switches knew about the other's routes.

If it were my network, i would concentrate on finding a way to leave all of the routing in one place (on the 5412).  This might be by providing extra bandwidth between the two switches, or using QoS to limit the impact of different VLANs' traffic on each other.


Hope that makes sense.