Ask the Expert: Implementing and Troubleshooting Virtual Switching System (VSS) on Cisco Catalyst Switches 4500 and 6500

[ciscomoderator]

Virtual Switching System (VSS) is network system virtualization technology that pools multiple Cisco Catalyst 6500 Series Switches into one virtual switch, increasing operational efficiency, boosting nonstop communications, and scaling system bandwidth capacity to 1.4 Tbps. At the initial phase, a VSS will allow two physical Cisco Catalyst 6500 Series Switches to operate as a single logical virtual switch called a virtual switching system 144. 
his session will provide an opportunity to learn and ask questions about how to implement, configure and troubleshoot VSS in Cisco Catalyst Switches 6500 and 4500.

Ask questions from Monday, September 7 to Friday, September 18, 2015

Featured Experts

InayathUlla Sharieff is a Customer support engineer in High-Touch Technical Services (HTTS) team supporting LAN Switching and Data center Products. His areas of expertise include Cisco Catalyst 2000,3000,4000 ,6500 and Cisco Nexus 7000 Switches. Shariff has over 8 years of industry experience working with large enterprise and Service Provider networks. He holds Bachelors in Computer Sciences degree and these Cisco  certifications: CCNA, CCNP (in Routing and Swtiching), and CCIE in R&S (# 43263). He is pursuing the CCIE in Data Centers.

Suresh  Vs is a Customer Support Engineer in High-Touch Technical Services (HTTS) at Cisco Bangalore, India. He has over 11 years of industry experience working with large Enterprise and Service Provider networks. He has been working with HTTS from past 4 years and supporting LAN Switching and Data center Products. His areas of expertise include Cisco Catalyst 2000, 3000, 4000, 6500 and Cisco Nexus 7000 Switches. Suresh holds a Bachelor's of Sciences in Electrical and Electronics Engineering from Madras University. He has these certifications: CCNA, CCNP, CCIE Data Center (# 46658).

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[Suresh Vinayagam Subramanian]

Hi,

The VSS1440 will allow up to two physical Cisco Catalyst 6500 Series Switches to operate as a VSS. The two physical chassis does not need to be identical in the type of modules installed or even type of chassis. For example, a WS-C6503-E chassis can be combined with a WS-C6513 chassis to form a VSS.

But that  chassis should support VS-S720-10G supervisor engines and WS-X6708-10G switching modules. And Both the switch supervisor should be identical .

you can see the hardware requirement in below links

http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst6500/ios/12-2SX/configuration/guide/book/vss.html#wp1053927

Chassis and Modules

Table 4-1 describes the hardware requirements for the VSS chassis and modules.

Table 4-1 VSS Hardware Requirements

Hardware	Count	Requirements
Chassis	2	The VSS is available on chassis that support VS-S720-10G supervisor engines and WS-X6708-10G switching modules. Note The two chassis need not be identical.
Supervisor Engines	2	The VSS requires Supervisor Engine 720 with 10-Gigabit Ethernet ports. You must use either two VS-S720-10G-3C or two VS-S720-10G-3CXL supervisor engine modules. The two supervisor engines must match exactly.
Switching Modules	2+	The VSS requires 67xx series switching modules. The VSS does not support classic, CEF256, or dCEF256 switching modules. In virtual switch mode, unsupported switching modules remain powered off.

VSL Hardware Requirements

The VSL EtherChannel supports only 10-Gigabit Ethernet ports. The 10-Gigabit Ethernet port can be located on the supervisor engine module or on one of the following switching modules:

•WS-X6708-10G-3C or WS-X6708-10G-3CXL

•WS-X6716-10G-3C or WS-X6716-10G-3CXL

•WS-X6716-10T-3C or WS-X6716-10T-3CXL

HTH
Regards,
VS.Suresh.
 

[Basavaraj Ningappa]

Hi Team,

Can you please share some knowledge what are the prerequisite for deploying VSS between 4500 switches. How do we check the peer information like module details and peer system details, and also would like to know few troubleshooting steps for VSS

Thanks

Basavarj

[InayathUlla Sharieff]

Hi basavaraju,

Please find article link below which is been created for tge catalyst 4000 switch with all the hardware and software requirement along with linecards:--

https://supportforums.cisco.com/document/124626/virtual-switching-system-vss-configuration-cisco-4500-series-switches

Hth

Inayath

[cks93]

Hi

1. Can the multiple dual-active detection links bundled together in a port-channel on C4500X?

2. Can the root bridge be set on a VSS pair with "spanning-tree vlan 1-4094 root primary" on the active switch and "spanning-tree vlan 1-4094 root secondary" on the standby?

Thanks

CK

[InayathUlla Sharieff]

CK,

1- Yes you can configure/have the multiple dual-active detection links budled together in a PO.

Ref:-

http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst4500/12-2/53SG/configuration/config/channel.pdf

http://www.netcraftsmen.com/cisco-vss-dual-active-detection/

2-

No you cant set this. As when you configure VSS there will be only one switch.

VSS is comprised of a single logical switch that advertises single STP bridge-ID and priority, regardless of which virtual-switch member is in the active state. 

More info on the STP of VSS:-

http://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/Campus/VSS30dg/campusVSS_DG/VSS-dg_ch3.html#wp1079779

HTH

regards

Inayath

[cks93]

Hi Inayath,

Thanks for replying. I think I did not make my first question clear. I want to ask if I use multiple links between the two VSS switches for Dual-Active Detection using fast hellos, can I bundle those links in an etherchannel? I have not seen any configuration in any cisco documentation that tells about if this can be done.

Thanks

CK

[Suresh Vinayagam Subramanian]

Hello CKS,

You can't use port-channel but you can use Up to four interfaces (directly connected) on each chassis can be configured. These interfaces must be physical interfaces, no logical ports (for example, SVI).. 

With 12.2(33)SXI, a Fast Hello detection mechanism was introduced. This is similar to IP-BFD, as it is a dedicated direct link heartbeat between the VSS switches. However, Fast Hello is a L2 connection and you can configure up to 4 non-VSL links. The two chassis will periodically exchange Fast Hello heartbeat packets that contain the switch state .

you can find this details in page 44 (Fast Hello Detection) .

Also you can find more details about VSS on below link .

http://www.cisco.com/c/dam/en/us/products/collateral/interfaces-modules/network-modules/white_paper_c11_429338.pdf

Hope this will be helpful for you.

HTH
Regards,
VS.Suresh.

[cks93]

Hi Suresh,

I am not talking about port-channeling of VSLs.  I am talking about port channeling of multiple fast-hello links. Can the multiple fast-hello links bundled together using port channel? I think not? If yes then can you refer me to a link. 

Thanks

ck

[InayathUlla Sharieff]

Hi Ck93,

I will take this question on behalf of Suresh.

Question:- I am talking about port channeling of multiple fast-hello links. Can the multiple fast-hello links bundled together using port channel?

Answer:- No you cannot have the port-channel on the interface were  Dual active fast-hello configured.

Let me show you the reason by giving the example:-

interface GigabitEthernet1/5/1
 description Dual-Active Detection >>>> Have configured the dual-active FH.
 no switchport
 no ip address
 no cdp enable
 dual-active fast-hello
end

Testing:

=======

1- Now when I try to configure the Port-Channel I dont see that option present on the interface:-

VSS(config-if)#int g1/5/1
VSS(config-if)#channel-gr?>>>> U can see that it doesnt recognize the command.
% Unrecognized command

2- Now I will remove the dual-active fast-hello config out of the interface and try to confiugre the po on this interface it will work:-

VSS(config)#int G1/5/1
VSS(config-if)#no  dual-active fast-hello >> Removed the config. 
VSS(config-if)#channel-group 1 ? >> Now I am able to configure.
  mode  Etherchannel Mode of the interface

3- Now lets first configure the PO and then try to configure the DA-Fast hello you can see it will throw an error and fast-hello command will not be accepted.

do sh run int g1/5/1

interface GigabitEthernet1/5/1
 description Dual-Active Detection
channel-group 1 mode active
+++ Now I will add the fast hello command+++

conf t

VSS(config-if)#dual-active fast-hello  >> cmd added but got error and PO config removed out of the interface.
WARNING: Interface GigabitEthernet1/5/1 placed in restricted config mode. All extraneous configs removed!
VSS(config-if)#

VSS(config-if)#do sh run int g1/5/1
Building configuration...

Current configuration : 152 bytes
!
interface GigabitEthernet1/5/1
 description Dual-Active Detection
 no switchport
 dual-active fast-hello >>>>>>>>>>> This has been added and PO config been removed.
end

HTH

Regards

Inayath

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[cks93]

Thanks Inayath and Suresh....

[susim]

Hi ,

As per below output we are in safe side ? 

What is dual-active recovery mode: No means ?

sho sw virtual dual-active summary
Pagp dual-active detection enabled: Yes
Fast-hello dual-active detection enabled: Yes
FEX dual-active detection enabled: Yes

No interfaces excluded from shutdown in recovery mode

In dual-active recovery mode: No

Thanks

[InayathUlla Sharieff]

Hi Support SBT,

Thanks for writing to us. The reason for the recovery mode saying as :NO is that you are not running into the recovery mode.(The VSS is working fine with active and standby switch configured to work in VSS mode). 

The status of recover mode will change to :YES only when the dual-acitve recovery has been triggered.

Example:-
VSS#show sw virtual dual-active su
Pagp dual-active detection enabled: Yes
Fast-hello dual-active detection enabled: Yes

No interfaces excluded from shutdown in recovery mode

In dual-active recovery mode: No >>>>>>>>>>>>>>>. Its says no.

Config:
switch virtual domain 200
switch mode virtual
switch 1 priority 250

VSL link:
int po1
switch virtual link1
no ip add

int po2
switch virtual link2

Dual-active method: Fast hello

Int g1/1
dual-active fast-hello

int g2/1
dual-active fast-hello

=======================Testing to prove the dual-active recovery mode to:- YES ======

I will disconnect the connection of VSL connecting between 2 switches.

As expected Switch 2 will take over the Active role now.( In VSS when the vls goes down the active will go into recovery mode hence now you will see the swith 1 in recover and recovery mode will be triggered and it will show as YES status.)

I will now reconnected the link back.

Switch 1 output

VSS(recovery-mode)#show switch virtual role
In dual-active recovery mode: Yes>>>>>>>>>>>>>>>>>>>>>>>>>. Now you can see the status as been changed to yes because it has triggered it.,
  Triggered by: Fast-hello detection
  Triggered on interface: Gi1/1

HTH
Regards
Inayath

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[susim]

Hi ,
output shows  " Fast-hello dual-active detection enabled " , but  there is no interface assigned  
as you mentioned in the previous post .Do we need to assign a separate physical interface ?

Int g1/1
dual-active fast-hello

int g2/1
dual-active fast-hello

VSS#show sw virtual dual-active su
Pagp dual-active detection enabled: Yes
Fast-hello dual-active detection enabled: Yes

[InayathUlla Sharieff]

Yes we required a seperate link for the dual-active fast-hello (It will be dedicated link between the 2 devices).

In my case above example the following interface are interconnected and been configured for dual-active fast-hello.

switch 1--G1/1

Switch 2- G2/1 

HTH

regards

Inayath

[susim]

Hi ,

The output shows  

" Fast-hello dual-active detection enabled: Yes" . So why do we need a separate physical link ?

That was my question 

Thanks