Configuring VSS Pair with Mec

[Mokhalil82]

Hi

I will be setting up 2 x 4500x switches as a VSS pair and then will have 2 MECS (Multi-chassis Etherchannels) down to 2 stacks of 3750x switches. I am preparing the config and would really appreciate is someone can verify I have put together the correct config. I don't have access to the switches yet so cannot test it.

So for the VSS config.......(Using virtual domain 10, channel group 3)

4500X-01
Switch virtual domain 10
Switch 1
mac-address use-virtual

Interface port-channel 3
switchport
switch virtual link 1
no shut

Interface range Tengig 1/1/15 - 16
switchport mode trunk
channel-group 3 mode on

Switch convert mode virtual

4500X-02
Switch virtual domain 10
Switch 2
mac-address use-virtual

Interface port-channel 3
switchport
switch virtual link 2
no shut

Interface range Tengig 1/1/15 - 16
switchport mode trunk
channel-group 3 mode on

Switch convert mode virtual

For Dual Active Detection......

Switch virtual domain 10
dual-active detection fast-hello
exit

Interface Tengig 1/1/14
dual-active fast-hello
no shut

Interface Tengig 2/1/14
dual-active fast-hello
no shut

Now for the MEC configs...... (Im using channel goups 1&2 on the 4500x vss pair and port-channel 1 on 3750 Stack1 and channel group on 3750x stack2)

Core 4500x
interface port-channel1
description MEC1-TO-3750X
switchport
switchport mode trunk

interface port-channel2
description MEC2-TO-3750X
switchport
switchport mode trunk

interface range Tengig 1/1/1 - 2/1/1
switchport mode trunk
channel-group 1 mode ON

interface range Tengig 1/1/2 - 2/1/2
switchport mode trunk
channel-group 2 mode ON

3750X Stack 1
Interface port-channel 1
Description MEC1-TO-4500X
switchport trunk encapsulation dot1q
switchport mode trunk

interface range Tengig 1/1/1 - 2/1/1
switchport trunk encapsulation dot1q
udld port aggressive
channel-group 1 mode ON

3750X Stack 2
Interface port-channel 2
Description MEC2-TO-4500X
switchport trunk encapsulation dot1q
switchport mode trunk

interface range Tengig 1/1/1 - 2/1/1
switchport trunk encapsulation dot1q
udld port aggressive
channel-group 2 mode ON

I am using mode ON for both ends, is this good practice or is it best using Active modes for LACP

Any help will be appreciated

[Reza Sharifi · Accepted solution]

Hi,

For the most part the config is correct.  There is one thing that needs to be modified. For the VSL link you are using po3 on both switches.  The port-channel numbers need to be different for each switch.

So, if you are using po3 for switch-1, you need to configure po4 on switch-2.

Have a look at the VSS config  section "Configuring VSL Port Channel and Ports"

This link is using po10 and 20.

Link:

http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst4500/15-1-2/XE_340/configuration/guide/config/vss.html

HTH

[Reza Sharifi]

Hi,

One more thing, for MEC, it is recommended to use LACP or PAgP.

HTH 

[Mokhalil82]

Hi Reza

Thanks for your feedback. I always tried to use the same numbers on either end for port-channels so wasn't aware they need to be different for VSS. But thanks again, ive learnt something new :-)