HSRP timers

[Patrick McHenry]

I always thought that setting the hello and hold timers to different values on HSRP partners would not allow it to work or atleast not allow preemtion to wor. It seems to work fine in lab. Am I missing something?

Thanks, Pat.

[andtoth]

Hi Patrick,

You can configure the HSRP timers, that's not an issue, even preemption will work.

Routers or access servers on which standby timer values are not configured can learn timer values from the active or standby router. The timers configured on an active router always override any other timer settings.

HSRP Timers

http://www.cisco.com/en/US/tech/tk648/tk362/technologies_tech_note09186a0080094afd.shtml#topic14

Configuring HSRP Authentication and Timers

http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/12.2_55_se/configuration/guide/swhsrp.html#wp1044417

Best regards,

Andras

[Patrick McHenry]

But I had one switch set as hello 3 hold 10 and the other hello msec 500 hold msec 1500 and it still worked. Are you saying that it only matters what the active router's timers are?

[andtoth]

Routers or access servers on which standby timer values are not configured can learn timer values from the active or standby router. The timers configured on an active router always override any other timer settings.

Andras

[Patrick McHenry]

So, it doesn't matter that the timers are set differently on the HSRP partners but, like Amit said, it is not recommended?

[Amit Aneja]

Andras,

I have got a ques for you. So, whatever we configure on standby router, if we do "show standby", should we see the same timers in the o/p on both active & standby?

Regards,

Amit

[Patrick McHenry]

In my lab I didn't. One routersaid 3 10 and the other was msec 500 msec 1500

[andtoth]

That might depend on the platform and software version and could be just cosmetic.

Andras

[Jeroen Huysmans]

Sorry to bump into this old thread...

---

@Patrick McHenry wrote:

In my lab I didn't. One routersaid 3 10 and the other was msec 500 msec 1500

---

you're probably running HSRPv1 and there is a subtle difference when talking about timers:

In HSRP version 1, millisecond timer values are not advertised or learned.

So yes, timers are advertised or learned in HSRPv1 unless you've configured msec timers.

Very confusing and I'm guessing this would/could cause unpredictable situations...

Jeroen

[andtoth]

Hi Amit,

You will see the same timer values on both the standby and active, those are advertised by the active.

The following is from a standby hsrp device which is a 6500:

#sh run int vlan777

interface Vlan777

ip address 192.168.43.7 255.255.255.0

standby 77 ip 192.168.43.3

standby 77 priority 50

standby 77 preempt

end

#sh standby vlan777

Vlan777 - Group 77

  Local state is Standby, priority 50, may preempt

  Hellotime 1 sec, holdtime 3 sec

  Next hello sent in 0.018

  Virtual IP address is 192.168.43.3 configured

  Active router is 192.168.43.2, priority 150 expires in 2.252

  Standby router is local

  1 state changes, last state change 00:00:35

  IP redundancy name is "hsrp-Vl777-77" (default)

As you can see, timers are not configured on the standby device, although they are set to hello 1 and hold 3 because it's set on the active.

If you configure it on the standby only, you will see the following:

#sh stand vlan777

Vlan777 - Group 77

  Local state is Standby, priority 50, may preempt

  Hellotime 3 sec (cfgd 1 sec), holdtime 10 sec (cfgd 5 sec)

  Next hello sent in 1.125

  Virtual IP address is 192.168.43.3 configured

  Active router is 192.168.43.2, priority 150 expires in 8.652

  Standby router is local

  1 state changes, last state change 00:04:53

  IP redundancy name is "hsrp-Vl777-77" (default)

Best regards,

Andras

Message was edited by: Andras Toth

[Amit Aneja]

Thanks Andras, I got it. I checked it & it does change.

[Patrick McHenry]

My lab did not work like this. I guess I will try it again. So, you are showing me that what ever I set the active timers to, the standby with take on the same values?

Thanks, Pat

I'm using 3750s with ip base software

[andtoth]

Hi Pat,

Yes your understanding is correct. The standby should learn and use the timer values advertised by the active hsrp device.

Which specific version do you run on the 3750 ?

Thanks,

Andras

[Patrick McHenry]

c3750-ipbasek9-mz.122-55.SE1.bin

[andtoth]

Hi Patrick,

I have tested it on a 3750 running 12.2(55)SE3 and the standby shows the actual timers, advertised by the active device.

When configured on the active and left at default on standby, instead of the default 3 and 10, it shows the configured 1 and 5.

#sh stand vl2

Vlan2 - Group 2

  State is Standby

    1 state change, last state change 00:01:27

  Virtual IP address is 167.167.167.254

  Active virtual MAC address is 0000.0c07.ac02

    Local virtual MAC address is 0000.0c07.ac02 (v1 default)

  Hello time 1 sec, hold time 5 sec

    Next hello sent in 0.432 secs

  Preemption disabled

  Active router is 167.167.167.1, priority 150 (expires in 4.768 sec)

  Standby router is local

  Priority 100 (default 100)

  Group name is "hsrp-Vl2-2" (default)

When configured on standby as well:

#sh stand vl2

Vlan2 - Group 2

  State is Standby

    1 state change, last state change 00:03:33

  Virtual IP address is 167.167.167.254

  Active virtual MAC address is 0000.0c07.ac02

    Local virtual MAC address is 0000.0c07.ac02 (v1 default)

  Hello time 1 sec (cfgd 2 sec), hold time 5 sec (cfgd 6 sec)

    Next hello sent in 0.640 secs

  Preemption disabled

  Active router is 167.167.167.1, priority 150 (expires in 5.072 sec)

  Standby router is local

  Priority 100 (default 100)

  Group name is "hsrp-Vl2-2" (default)

Best regards,

Andras