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load balancing vlan with out configuring spanning tree root

Level 1
Level 1


I have a typical scenario here. Can  some one help me to find out hw to impv the performance  of server vlan (locally significant)  from other vlans.

DS- A,DS- B &  Network 10.10.251.x/24 residing in Access Switch C(AS-C)

DS-A and DS-B are running in Pvst+ , with DS-A root for odd vlan ,DS-B root for even vlan.

DS-A is configured for 10.10.251.x/24 , and gi3/5 is connected to AS-C.  DS-B will learn 10.10.251.x/24 via trunk.

10.10.251.x/32 running with default priority and cost,

I can see that RX load  on the gi3/5 is always above 245/255.

I am looking for ways to reduce the RX load the gi3/5 of DS-A which in turn connects to AS-C

Thanks for reading and thanks in advance for the suggestions.


3 Replies 3

Antonio Knox
Level 7
Level 7

Increase the cost of the vlan on that port

spanning vlan 1 cost 300

This should force traffic for that vlan to go through DS-B link to AS-C.  You can do this for any vlan that you want to force through DS-B.

Please rate if helpful.

Thanks for the reply.

Let me reframe my question,  The server vlan 10.10.251.x/24 doesn't have direct connectivity to the DSB.

AS-C is directly connected to DSA in port gi3/5 .  in other words, AS-C has only one uplink which is DS-A. There is no phy connection bet ASC and DSB

Vlan 251 is communicating  via trunk port between DSA and DSB.

ASC -->DSA  <> DSB is connection. 

Can you help me with a solution. Currently phy connectivity to ASC-DSB is impossible .Can we achieve this by any fine tuning in the switches ?

Note: Yes I said the both DSA and DSB are root for some even and odd vlan. But vlan251 is doesn't belongs to that



I can't think of much that can lower the RX load in this case besides filtering traffic to stop what you may deem as unecessary traffic.  PVST is supposed to help with this by letting you load balance the vlans, but if there's only one uplink, there really isn't much you can do outside of lowering traffic with ACLs or giving certain traffic priority via QoS, and both options have a processing trade-off.

Hope that helps.

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