VSS Dual Active detection

Answered Question
Nov 18th, 2008

Hi,

Upon detecting the dual-active condition, the original active chassis enters into recovery mode and

brings down all of its interfaces except the VSL and nominated management interfaces, effectively

removing the device from the network.

To nominate specific interfaces to be excluded from being brought down during dual-active

detection recovery, use the following commands:

vss(config)#switch virtual domain 10

vss(config-vs-domain)#dual-active exclude interface gigabitEthernet

1/5/3

Question1 :Is this mean that if I have some Servers that has one connection to one of the VSS switches , and Dual Active detection occure , the servers ports will be shutdown ??

Q2: Do I have to exclude all ports that have servers(with one link)from the dual active detection action.

I have this problem too.
0 votes
Correct Answer by gnijs about 8 years 1 week ago

Q1: yes. If you have single-connected servers and you arrive in a "dual-active" scenario, yes, some servers will loose connectivity.

But this is by design: if you loose the VSL, you CANNOT keep both switches active. This will mess up routing and actually impact BOTH chassis'. so you have to make a choice.

BTW you don't have redundant supervisors also. So a SV failure would also blackhole the complete chassis (with single connected devices).

Recommendation: don't single connect a server in VSS. Dual connect all servers or use a dual-connected access layer (ie. C3750G switches)

Q2: No. You don't. Even if you exclude it, it would be blackholed anyway. The "exclude" feature was designed to keep one interface up for management. Because all ports shut down, you loose connectivity to the switch. You can configure one port with a L3 ip address and exclude this port from dual-active. In the event of VSL failure, you can get to the chassis via this port.

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Correct Answer
gnijs Tue, 11/18/2008 - 05:37

Q1: yes. If you have single-connected servers and you arrive in a "dual-active" scenario, yes, some servers will loose connectivity.

But this is by design: if you loose the VSL, you CANNOT keep both switches active. This will mess up routing and actually impact BOTH chassis'. so you have to make a choice.

BTW you don't have redundant supervisors also. So a SV failure would also blackhole the complete chassis (with single connected devices).

Recommendation: don't single connect a server in VSS. Dual connect all servers or use a dual-connected access layer (ie. C3750G switches)

Q2: No. You don't. Even if you exclude it, it would be blackholed anyway. The "exclude" feature was designed to keep one interface up for management. Because all ports shut down, you loose connectivity to the switch. You can configure one port with a L3 ip address and exclude this port from dual-active. In the event of VSL failure, you can get to the chassis via this port.

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