How to fix spanning Tree Protocol block port in HSRP

[Sotheng Se]

Dear Support,

I'm implementing HSRP on core switch in my network, but spanning tree always block one port on the layer 2 switch.
my question is how to make Spanning tree don't block port on layer 2 switch or its mean that we can use block port for forwarding port.
Pls help find network diagram in attached file.

Thanks,

Best regards.

[Mark Malone · Accepted solution]

Hi

its blocking to prevent a loop , the hsrp traffic will be going to the vip address anyway for the active router so why are you concerned which port stp has blocked as long as its not breaking traffic or do you want stp to use another path at layer 2

There will always be a blocked port in that design or you will end up with layer 2 loop , if you want to set another port to be the blocked port you can set the cost on a less preferred link by going to each sides interface and setting -- spanning-tree cost 2500 , this will make that link less preferred and move to blocking , this will cause a disruption as the calculation at layer 2 takes place in stp

[Sotheng Se]

Hi

Thanks for your reply , and now i got it.

Best Regard,

[Sotheng Se]

Dear Support,

Base on network diagram in attached file normally STP will block one port to prevent loop. But what is the solution if we want to use port fa0/2 and fa0/3 on Switch0 (both uplinks port) to be forward traffic (forwarding port) to increase our bandwidth?

Please kindly check attached file for more information.

Thanks you!

Best Regards,

[Mark Malone]

Hi

you would either need to have vss switches instead of 3560s you could then use a port-channel one link to each switch connected to each 3560 or the switches were capable of vpc like nexus

unfortunately you have 3560s so neither of those options will work for you , what you could have is 2 or more links each side of 2960 connecting to each 3560 in port channel mode , there capable of up to 8 links max each side for more throughput

This doc shows how , you can force it with 1 command though under each interface channel-group 1 mode on as an example or use pagp or lacp etherchannels

http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750x_3560x/software/release/12-2_55_se/configuration/guide/3750xscg/swethchl.html