[c-nsp] Cisco 6509 VRRP no preemption

Tue Jul 31 16:50:21 EDT 2007

Router configured with no preempt will never attempt to transfer the
master role in presence of the existing Master. Do you have spanning
tree enabled on the segment connecting R1 to R2?
Most likely you rebooted the second switch and it caused the spanning
tree reconvergence on the trunk that connects two switches together.
VRRP group 10 on R1 became active before it had a chance to detect the
existing group with the same ID running on R2.

Please post:

show spanning-tree vlan 1100 detail

-----Original Message-----
From: Gier, Menno de (Menno) [mailto:mdegier at alcatel-lucent.com] 
Sent: Tuesday, July 31, 2007 3:33 PM
To: cisco-nsp at puck.nether.net
Cc: Tolstykh, Andrew
Subject: RE: [c-nsp] Cisco 6509 VRRP no preemption

We don't want the router to switch back if the original master recovers.

My understanding from no preemption is that there will no switch back
unless manual override or if the 'new' master fails.

We use 
interface Vlan1100
 ip address 10.0.0.2 255.255.255.0
 vrrp 10 ip 10.0.0.1
 no vrrp 10 preempt
 vrrp 10 priority 200

Below is the output.

/M

R1#show vrrp all
Vlan1100 - Group 10
  State is Master
  Virtual IP address is 10.0.0.1
  Virtual MAC address is 0000.5e00.010a
  Advertisement interval is 1.000 sec
  Preemption disabled
  Priority is 200
  Master Router is 10.0.0.2 (local), priority is 200
  Master Advertisement interval is 1.000 sec
  Master Down interval is 3.218 sec

R1#show vrrp interface Vlan 1100
Vlan1100 - Group 10
  State is Master
  Virtual IP address is 10.0.0.1
  Virtual MAC address is 0000.5e00.010a
  Advertisement interval is 1.000 sec
  Preemption disabled
  Priority is 200
  Master Router is 10.0.0.2 (local), priority is 200
  Master Advertisement interval is 1.000 sec
  Master Down interval is 3.218 sec

R2#show vrrp all
Vlan1100 - Group 10
  State is Backup
  Virtual IP address is 10.0.0.1
  Virtual MAC address is 0000.5e00.010a
  Advertisement interval is 1.000 sec
  Preemption disabled
  Priority is 100
  Master Router is 10.0.0.2, priority is 200
  Master Advertisement interval is 1.000 sec
  Master Down interval is 3.609 sec (expires in 2.681 sec)

R2#show vrrp interface Vlan 1100
Vlan1100 - Group 10
  State is Backup
  Virtual IP address is 10.0.0.1
  Virtual MAC address is 0000.5e00.010a
  Advertisement interval is 1.000 sec
  Preemption disabled
  Priority is 100
  Master Router is 10.0.0.2, priority is 200
  Master Advertisement interval is 1.000 sec
  Master Down interval is 3.609 sec (expires in 2.717 sec)
#

-----Original Message-----
From: Tolstykh, Andrew [mailto:ATolstykh at integrysgroup.com] 
Sent: dinsdag 31 juli 2007 22:18
To: Gier, Menno de (Menno); cisco-nsp at puck.nether.net
Subject: RE: [c-nsp] Cisco 6509 VRRP no preemption

Please post the output of the VRRP interface configuration and "show
vrrp all" commands.

By default VRRP will preempt for all configured groups.
You need to disable preemption explicitly with no vrrp [group] preempt.

By default, a preemptive scheme is enabled whereby a higher priority
virtual router backup that becomes available takes over for the virtual
router backup that was elected to become virtual router master. You can
disable this preemptive scheme using the no vrrp preempt command. If
preemption is disabled, the virtual router backup that is elected to
become virtual router master remains the master until the original
virtual router master recovers and becomes master again. 

ISP1-INET-RTR1#sho vrrp all 
FastEthernet0/0 - Group 1  
  State is Master  
  Virtual IP address is 160.1.1.2
  Virtual MAC address is 0000.5e00.0101
  Advertisement interval is 1.000 sec
  Preemption enabled
  Priority is 100 
  Master Router is 160.1.1.1 (local), priority is 100 
  Master Advertisement interval is 1.000 sec
  Master Down interval is 3.609 sec

no vrrp 1 preempt

ISP1-INET-RTR1#sho vrrp all 
FastEthernet0/0 - Group 1  
  State is Master  
  Virtual IP address is 160.1.1.2
  Virtual MAC address is 0000.5e00.0101
  Advertisement interval is 1.000 sec
  Preemption disabled
  Priority is 100 
  Master Router is 160.1.1.1 (local), priority is 100 
  Master Advertisement interval is 1.000 sec
  Master Down interval is 3.609 sec

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Gier, Menno de
(Menno)
Sent: Tuesday, July 31, 2007 2:25 PM
To: cisco-nsp at puck.nether.net
Subject: [c-nsp] Cisco 6509 VRRP no preemption

All,

We have two Cisco 6509 switches (A1 and A2) running VRRP over a trunk
between both switches. We have configured VRRP with no vrrp preemption.

After a power down of switch A1, which was selected as master VRRP, the
VRRP moved to the switch A2, as it should be.

After power up it of the switch A1 it became Master for the VRRP again
and the other switch A2 became backup unexpectedly.

Is this normal behavior of VRRP after a reboot?

We have configured VRRP to be non preemption to avoid a second traffic
interruption. We want to have the switch-over taking place in service
hours under our control.

Thanks in advance,

/mg 

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