08-13-2010 05:41 AM - edited 03-06-2019 12:28 PM
I am testing a few possibilities about Failover with SUP720-VSS
this is my config
switch virtual domain 100
switch mode virtual
switch 1 priority 254
VSL betwenn both 10G Portsof the SUPs as Portchannel
interface Port-channel1
no switchport
no ip address
switch virtual link 1
mls qos trust cos
no mls qos channel-consistency
!
interface Port-channel2
no switchport
no ip address
switch virtual link 2
mls qos trust cos
no mls qos channel-consistency
and one dual-active fast-hello Port
interface GigabitEthernet1/7/8
no switchport
no ip address
dual-active fast-hello
interface GigabitEthernet2/7/8
no switchport
no ip address
dual-active fast-hello
All is working fine.
Now I cut the connections of VSL
Because of dual-active fast-hello detection:
local Switch 1 is going in shutdown
local Switch 2 is getting active
Why the Switch 2 is getting active and not Switch1?
Is there a parameter where I can specify this?
The command "switch 1 priority 254 " seems to be not in conjunction with this.#
I reconnect the VSL connection
On Switch1
Switch Switch Status Preempt Priority Role Session ID
Number Oper(Conf) Oper(Conf) Local Remote
------------------------------------------------------------------
LOCAL 1 UP FALSE(N ) 254(254) ACTIVE 0 0
REMOTE 2 UP FALSE(N ) 100(100) ACTIVE 4974 6188
In dual-active recovery mode: Yes
Triggered by: Fast-hello detection
Triggered on interface: Gi1/7/8
VSS(recovery-mode)#show switch virtual redundancy mismatch
No Config Mismatch between Active and Standby switches
On Switch2
VSS#show switch virtual role
Switch Switch Status Preempt Priority Role Session ID
Number Oper(Conf) Oper(Conf) Local Remote
------------------------------------------------------------------
LOCAL 2 UP FALSE(N ) 100(100) ACTIVE 0 0
REMOTE 1 UP FALSE(N ) 254(254) ACTIVE 6188 4974
In dual-active recovery mode: No
VSS#show switch virtual redundancy mismatch
No Config Mismatch between Active and Standby switches
Why is there no mechanism which recreate a normal functional VSS?
I want to do no interaction in such case.
Solved! Go to Solution.
08-13-2010 06:41 AM
Marcus,
It is not recommended to use preemption in the data center; typically, the VSS member switches uses identical line card configurations and reside in a dual-homed environment, where favoring one system over another is irrelevant.
HTH
Reza
08-13-2010 06:48 AM
Hello,
Let me try to answer your questions:
Now I cut the connections of VSL
Because of dual-active fast-hello detection:
local Switch 1 is going in shutdown
local Switch 2 is getting active
Why the Switch 2 is getting active and not Switch1?
This occurrs because during normal VSS operation, prior to the dual-active condition, Switch1 was the Active switch and Switch2 was the Hot-Standby.
When dual-active condition is detected via Fast-Hello mechanism the old-active switch disables all the local interfaces except the loopback to avoid the instability caused by dual-active situation. It also removes routing and STP instances. After that it remains out of the network.
Is there a parameter where I can specify this?
This situation is always the same. The old-active switch will be shutdown and the old-Hot-Standby switch will become active.
I reconnect the VSL connection
Why is there no mechanism which recreate a normal functional VSS?
I want to do no interaction in such case.
Once VSL is restored, Switch1 reloads and comes up in standby mode. Then, RRP will determine that the old-active switch Switch1 must be the Hot-Standby switch now. RRP considers there is no need to change the role of the new-active switch (Switch2) and cause more data loss.
The way the Active and Hot-Standby roles are elected depends on the order the switches are initialized. If they boot up at the same time, the switch with lower switch ID will be the Active switch.
If one of the switches is desired to be the Active one under all conditions, preemption must be configured on it and the desired Active switch must have the highest switch ID.
However, enabling preemption is very dangerous for the network stability because it forces multiple reboots of the VSS member.
Hope this helps.
08-13-2010 06:41 AM
Marcus,
It is not recommended to use preemption in the data center; typically, the VSS member switches uses identical line card configurations and reside in a dual-homed environment, where favoring one system over another is irrelevant.
HTH
Reza
08-13-2010 06:48 AM
Hello,
Let me try to answer your questions:
Now I cut the connections of VSL
Because of dual-active fast-hello detection:
local Switch 1 is going in shutdown
local Switch 2 is getting active
Why the Switch 2 is getting active and not Switch1?
This occurrs because during normal VSS operation, prior to the dual-active condition, Switch1 was the Active switch and Switch2 was the Hot-Standby.
When dual-active condition is detected via Fast-Hello mechanism the old-active switch disables all the local interfaces except the loopback to avoid the instability caused by dual-active situation. It also removes routing and STP instances. After that it remains out of the network.
Is there a parameter where I can specify this?
This situation is always the same. The old-active switch will be shutdown and the old-Hot-Standby switch will become active.
I reconnect the VSL connection
Why is there no mechanism which recreate a normal functional VSS?
I want to do no interaction in such case.
Once VSL is restored, Switch1 reloads and comes up in standby mode. Then, RRP will determine that the old-active switch Switch1 must be the Hot-Standby switch now. RRP considers there is no need to change the role of the new-active switch (Switch2) and cause more data loss.
The way the Active and Hot-Standby roles are elected depends on the order the switches are initialized. If they boot up at the same time, the switch with lower switch ID will be the Active switch.
If one of the switches is desired to be the Active one under all conditions, preemption must be configured on it and the desired Active switch must have the highest switch ID.
However, enabling preemption is very dangerous for the network stability because it forces multiple reboots of the VSS member.
Hope this helps.
08-17-2010 06:49 AM
Because of using the SXI IOS Version there is no problem with preemption because it isn't available...
Thank you for your answers - all of it I could reproduce :-)
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