Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

VRRP active and backup Router behaviour

Hi Everyone,

I have set up vrrp between 2 routers for testing.

R1 has this config

2691Router#sh vrrp

FastEthernet1/1 - Group 20

  State is Backup

  Virtual IP address is 192.168.7.3

  Virtual MAC address is 0000.5e00.0114

  Advertisement interval is 1.000 sec

  Preemption enabled, delay min 60 secs

  Priority is 100

  Master Router is 192.168.7.2, priority is 100

  Master Advertisement interval is 1.000 sec

  Master Down interval is 3.609 sec (expires in 3.369 sec)

2691Router# sh run int fa1/1

Building configuration...

Current configuration : 256 bytes

!

interface FastEthernet1/1

ip address 192.168.7.1 255.255.255.0

duplex auto

speed auto

vrrp 20 ip 192.168.7.3

vrrp 20 preempt delay minimum 60

end

***********************************************************************************************************************

R2   is master with config

R2#                      sh vrrp

Ethernet1/1 - Group 20

  State is Master

  Virtual IP address is 192.168.7.3

  Virtual MAC address is 0000.5e00.0114

  Advertisement interval is 1.000 sec

  Preemption enabled, delay min 60 secs

  Priority is 100

  Master Router is 192.168.7.2 (local), priority is 100

  Master Advertisement interval is 1.000 sec

  Master Down interval is 3.609 sec

R2# sh run int eth

R2# sh run int ethernet 1/1

Building configuration...

Current configuration : 138 bytes

!

interface Ethernet1/1

ip address 192.168.7.2 255.255.255.0

half-duplex

vrrp 20 ip 192.168.7.3

vrrp 20 preempt delay minimum 60

end

Question

Right now 1 is master and other is backup .

Need to confirm if this is correct behaviour or not??

As R2 is master even though priority is 100 on both routers so R2 became master as it has higher IP address 192.168.7.2??????????????

***********************************************************************************************************

Question

On VRRP it says when you config timer on master then backup router also follows those hello timers.

But when i config the advertise  timer on master then both routers R1 and R2 becomes master and they show different timers .Need to know why this happens????????

Thanks

Mahesh

Everyone's tags (4)
1 ACCEPTED SOLUTION

Accepted Solutions

VRRP active and backup Router behaviour

Mahesh,

The virtual address in vrrp can be assigned as the physical address of a real interface. In other words, if you have 192.168.7.1 as in R1, then you can assign 192.168.7.1 as the vIP unlike with HSRP where it has to be different. When vrrp is assigned a virtual address that's equal to the real address, that router becomes the master. If the router were to go down, preemption is automatically enabled by default in vrrp and causes the router with the next higher priority to take over. The problem that I think you're seeing is that there's no real ip of 192.168.7.3 being used. In that case, neither of these are really being seen as the master of the group. So because of this, since both priorities are the same, the next check is going to be the highest ip address of the group will become the master. If you want to change this behavior, you can set the priority of the one that you want as the primary to something higher than 100 and it will take over as master after your configured time of 60 seconds.

The timers between the routers in the group need to match. The master is the router that controls the timers, so when you change the timer on the master you can learn the timers on the backup or set the timer to the same interval as the other router. The default is 1 second for advertisment. From what I see, if you change the backups timer, it becomes master. Now with 2 masters, you can't change the other (original master) timer to learn from the original master because it seems that the priority and highest address still comes into play. With the original master, you'd have to send the different timer or change your priority to prefer the other router as master before sending the timer from it. On the other router (whichever backup you want) you would need to either learn (vrrp timers learn) or set your timer manually to the timer that's being sent from the master.

HTH,

John

HTH, John *** Please rate all useful posts ***
3 REPLIES
New Member

VRRP active and backup Router behaviour

Hi Mahesh,

Can you share the physical setup first...

HTH,

Sukanya

VRRP active and backup Router behaviour

Mahesh,

The virtual address in vrrp can be assigned as the physical address of a real interface. In other words, if you have 192.168.7.1 as in R1, then you can assign 192.168.7.1 as the vIP unlike with HSRP where it has to be different. When vrrp is assigned a virtual address that's equal to the real address, that router becomes the master. If the router were to go down, preemption is automatically enabled by default in vrrp and causes the router with the next higher priority to take over. The problem that I think you're seeing is that there's no real ip of 192.168.7.3 being used. In that case, neither of these are really being seen as the master of the group. So because of this, since both priorities are the same, the next check is going to be the highest ip address of the group will become the master. If you want to change this behavior, you can set the priority of the one that you want as the primary to something higher than 100 and it will take over as master after your configured time of 60 seconds.

The timers between the routers in the group need to match. The master is the router that controls the timers, so when you change the timer on the master you can learn the timers on the backup or set the timer to the same interval as the other router. The default is 1 second for advertisment. From what I see, if you change the backups timer, it becomes master. Now with 2 masters, you can't change the other (original master) timer to learn from the original master because it seems that the priority and highest address still comes into play. With the original master, you'd have to send the different timer or change your priority to prefer the other router as master before sending the timer from it. On the other router (whichever backup you want) you would need to either learn (vrrp timers learn) or set your timer manually to the timer that's being sent from the master.

HTH,

John

HTH, John *** Please rate all useful posts ***
New Member

VRRP active and backup Router behaviour

Hi John,

Thanks for detailed explanation.

Issue is fixed now.

In VRRP hello timers has to be matched to become master and backup.

When i config the timer on master then both became masters as they had different hello times.

So  under other router i config the hello timer to learn from master.

Now  VRRP is working fine 1 as MAster and other as Backup.

MAny thanks again for detailed explanation

Regards

MAhesh

1128
Views
0
Helpful
3
Replies