VSL link upgrade from 10 to 40 Gb

[DaniloB]

Hi all,

On a couple of C9500 40x in VSS I need to replace the 10Gb VSL links with 40Gb links. So I need to go from here:

stackwise-virtual
domain 255

interface TenGigabitEthernet1/0/39
 stackwise-virtual link 1
!
interface TenGigabitEthernet1/0/40
 stackwise-virtual link 1

!

interface TenGigabitEthernet2/0/39
 stackwise-virtual link 1

interface TenGigabitEthernet2/0/40
 stackwise-virtual link 1

To here:

stackwise-virtual
domain 255

interface FortyGigabitEthernet1/1/1
 stackwise-virtual link 1
!
interface FortyGigabitEthernet1/1/2
 stackwise-virtual link 1

!

interface FortyGigabitEthernet2/1/1
 stackwise-virtual link 1

interface FortyGigabitEthernet2/1/2
 stackwise-virtual link 1

What's the correct procedure? Is there a way to avoid service disruption?

[Reza Sharifi]

Hi,

Since you can not have a mix of 10Gig and 40Gig as part of the VSL, you would need a maintenance window to disconnect the 10Gigs and replace them with 40s. You may have to reload the switches in order for the 40Gig interface to take over.

HTH

[DaniloB]

Hi. What if I use different VSL link IDs? Would creating an additional links set, and then removing the existing links, minimize downtime?

interface FortyGigabitEthernet1/1/1
 stackwise-virtual link 2
!
interface FortyGigabitEthernet1/1/2
 stackwise-virtual link 2

!

interface FortyGigabitEthernet2/1/1
 stackwise-virtual link 2

interface FortyGigabitEthernet2/1/2
 stackwise-virtual link 2

[Reza Sharifi]

Hi,

Not sure if that complicates things more, as you may confuse the stack with multiple IDs, and if that happens you will have a longer maintenance window. I would configure all the 40Gig ports ahead of time, have the cables ready, and switch them in a window. 

Also, just FYI, you don't need 40Gig of bandwidth for VSL. If all access switches are connected to both core switches, 2 10Gig interfaces are more than enough.

HTH

[Joseph W. Doherty]

Just curious, why the need for the bandwidth upgrade as in normal operation VSL shouldn't be carrying traffic?

[DaniloB]

Not if you need SPAN. Capturing VLAN-sourced traffic will send the traffic to the destination port over the VSL link, if necessary.