VSS Best Practice for minimum outage

Mohit Chauhan · ‎01-14-2019

Hi all,

I have to add new chassis (4507 R+E) to an existing 4506E chassis which is currently running in standalone mode.

Since it is a core switch, I wanted to go with an approach that has minimum outages.

My idea was to do the following with the below sequence:

1. Backup of the current config of the standalone chassis.

2. Configure the new chassis with VSS with domain priority as 200. (Hold back on the reload.)

3. Configure the old chassis with VSS (keeping domain priority as 100 by default).

4. Reload both switches and patch the VSS and DA links while the switches are booting up.

Any comments or suggestions would be highly appreciated.

Thanks.

balaji.bandi · ‎01-14-2019

On high level you are in right direction, another support document for your reference.

https://community.cisco.com/t5/networking-documents/virtual-switching-system-vss-configuration-for-cisco-4500-series/ta-p/3147865

adding to your orginal steps :

1. Check you have latest and stable IOS in place on both the switches.

2. How is Access switches connected review the configuration (if it is L2)

3. keep backup and roll back plan in ready, in case if you enounter any issue, you want to bring back to as orginal postion where everything working.

4. always caputer all the logs in console if anything go wrong can be used for resolve the issue.

5. check the VSL link cable are tested, if not you get in to split brian situation.

good luck..keep us posted how it goes.

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Mark Malone · ‎01-14-2019

Hi
I thought in VSS the chassis can be different but they must contain same amount of slots and same blades each side , so mixing a 4507 and 4506 may not work

From a doc
The two chassis must have the same number of slots. However, +E and -E chassis can be mixed.

balaji.bandi · ‎01-14-2019

@Mark Malone -- good catch, sorry i was in impression both are same models. i support that statement..

From the 4500 configuration guide -

Chassis

2

VSS is available on a Catalyst 4500-X switch

Note The two chassis must have the same number of slots. However, +E and -E chassis can be mixed.

full link -

http://www.cisco.com/en/US/customer/docs/switches/lan/catalyst4500/15.1.2/XE_340/configuration/guide/vss.html#wp1053927

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Mohit Chauhan · ‎01-14-2019

@Mark Malone wrote:
Hi
I thought in VSS the chassis can be different but they must contain same amount of slots and same blades each side , so mixing a 4507 and 4506 may not work

From a doc
The two chassis must have the same number of slots. However, +E and -E chassis can be mixed.

Thanks for the reply. However, going by the latest release, we should be able to mix the chassis now as long as the SUP's are the same.

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst4500/XE3-9-0E/15-25E/configuration/guide/xe-390-configuration/vss.html#23715

The above link also talks about the how you can use "Quad-Supervisor (In-chassis Standby Supervisor Engine) Support" using different combinations of chassis.

Thanks.

Mark Malone · ‎01-14-2019

The sups would have to be the same anyway in VSS or it definitely wont work the whole point of VSS is its an identical replica of the 2 switches acting logically as one for failover purposes and extra throughput and compute power , i dont see where in that doc it states you can use a 6 slot module with a 7 slot module , quad sups in VSS is overkill in my opinion , weve been running VSS last 10 years on multiple platforms 45,65 etc , its a waste of money using 4 sups in 2 switches because once your LAN is cabled correctly you should still have access always , the likely event of 2 sups going same time on 2 switches is very high id say as there stable generally

Mohit Chauhan · ‎01-14-2019

@Mark Malone wrote:
The sups would have to be the same anyway in VSS or it definitely wont work the whole point of VSS is its an identical replica of the 2 switches acting logically as one for failover purposes and extra throughput and compute power , i dont see where in that doc it states you can use a 6 slot module with a 7 slot module , quad sups in VSS is overkill in my opinion , weve been running VSS last 10 years on multiple platforms 45,65 etc , its a waste of money using 4 sups in 2 switches because once your LAN is cabled correctly you should still have access always , the likely event of 2 sups going same time on 2 switches is very high id say as there stable generally

The point below where it mentions chassis...."can differ in the number of slots in the chassis"

"Asymmetric chassis support

Ensure that both participating switches in the VSS have the same supervisor engine type. The chassis can differ in type (i.e., +E and -E chassis can be in a single VSS) and also can differ in the number of slots in chassis.

"

I agree Quad-Sup VSS mode would be an overkill, but I only mentioned that here cos the matrix showing the different combinations of chassis. If it is supported in the Quad-Sup VSS, shouldn't it be supported in the basic VSS mode as well then?

The only reason we are doing a mismatch cos the current 6 slot chassis is still fairly new and wanted to save some cost for now by just buying one chassis at this stage.

Mark Malone · ‎01-14-2019

Hmm i read it different from this doc and i totally understand why your trying to use it especially if new and not out of support , below its saying it must be same slot count and you can use different chassis then

Asymmetric Chassis Support

Catalyst 4500 and Catalyst 4500-X VSS require the same supervisor engine type in both chassis. The chassis must contain the same number of slots, even if their linecards differ or their slots are empty. Provided the number of slots in the two chassis match, the chassis can differ in type (that is, +E and -E chassis can be in a single VSS).

https://www.cisco.com/c/en/us/support/docs/switches/catalyst-4500-series-switches/118597-config-vss-00.html#anc4

Leo Laohoo · ‎01-14-2019

Here's a "good practice":
1. Don't use ISSU; and
2. Don't use FSU/eFSU

Mohit Chauhan · ‎01-15-2019

@Leo Laohoo wrote:
Here's a "good practice":
1. Don't use ISSU; and
2. Don't use FSU/eFSU

Thanks. Yeah I am planning to upgrade the old chassis to match the IOS on the new chassis in a simple manner just like we do for any edge switches like 3850,3750X...

Once I achieve that, then only get to the VSS part.

balaji.bandi · ‎01-15-2019

yes you can do offline and make it VSS, so you do not need another downtime for upgrade.

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