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Community Member

Port Channel 2960 Stack to 4500X VSS Stack

I have a stack of three 2960s using stack wise cables to make them into one logical switch.  I have two 4500x switches stacked via VSS. 

The 2960 top switch will be trunked to the 4500x top switch and the 2960 bottom switch will be trunked to the 4500x bottom switch.
 

Is it required that I port channel the trunk ports on each stack?  If I don't port channel these ports, will it be a basic STP block on one port?  Is it recommened that I port channel these ports?

 

Thanks for your help

8 REPLIES

Hey,You may or may not

Hey,

You may or may not configure port-channel these links depending on your requirements.

If you don't bundle them then STP will block the alternate link, however its recommended to have port-channel as you will be able to utilize the bandwidth available of other link.

HTH.

Regards,

RS.

Community Member

Thank you rajeevsh.  Is there

Thank you rajeevsh.  Is there an added risk to utilizing the port-channel configuration compared to relying on STP?

None, so go for etherchannel

None, so go for etherchannel :)

HTH.

Regards,

RS.

Community Member

Rajeevsh, If we don't want to

Rajeevsh,

 

If we don't want to rely on etherchannel hello negotitations between stacks, do you recommend we use the "on" mode?  This will give us more manual control?

Hey,Surely you may use ON

Hey,

Surely you may use ON mode as it will not use the negotiation used by ether-channel protocols.

Regards,

RS.

Community Member

rajeevsh,We are cuurently

rajeevsh,

We are cuurently using a Cisco phone system.  We setup auto qos on the switch ports including the uplink trunk ports.  When we setup auto qos voip trust on the uplink trunk port while the port is a member of a port channel, it does not let us.  We have to apply the auto qos voip trust beforeewe add the port to a port channel.  Will the port still honor the voip qos when it is a member of the port channel?  Below is the configuration.

 

interface TenGigabitEthernet1/0/1

switchport mode trunk

srr-queue bandwidth share 1 30 35 5

priority-queue out

mls qos trust dscp

auto qos trust

channel-group 2 mode on

 

Yes it will honor the voip

Yes it will honor the voip qos even after bundling in port-channel. For reference i am adding snippet from my switch:

WS-C3750V2-48PS-1#sh run int f1/0/36
Building configuration...

Current configuration : 167 bytes
!
interface FastEthernet1/0/36
 srr-queue bandwidth share 10 10 60 20
 priority-queue out
 mls qos trust cos
 auto qos voip trust
 channel-group 1 mode passive
end

!
!

WS-C3750V2-48PS-1#sh mls qos interface f1/0/36
FastEthernet1/0/36
trust state: trust cos
trust mode: trust cos
trust enabled flag: ena
COS override: dis
default COS: 0
DSCP Mutation Map: Default DSCP Mutation Map
Trust device: none
qos mode: port-based

!

HTH.

Regards,

RS.

Community Member

One last thing that confused

One last thing that confused us is that when we enter "auto qos voip trust" to the uplink/trunk interface, it changes it to "auto qos trust" when we view the running config.  Do you know why this happens?  is it the same thing?

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