HSRP addresses in different subnets

Answered Question
Apr 9th, 2010

Hi all


I have 2 internet routers on site by a ISP, I have noticed that the main interfaces on both routers are in the same subnet, as per normal, and there is a group with a virtual address in this subnet as I would expect. However there is another group configured on the same interface where the standby IP address is not in the same subnet as the real address! , Will this really work?


Many thanks


Carl

Correct Answer by shailesh.h about 6 years 10 months ago

You may use sub interface to achieve the same result... as thre are couple of limitations while particip

ating in dynamic routing protocol like OSPF.


If you are not planning to use OSPF in near future then you can continue with the configuration currently available...


Cheers!

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carl_townshend Fri, 04/09/2010 - 06:46

Basically one ip is 194.73.x.x and the other 194.74.x.x but the masks are /28

cheers

#sh standby

FastEthernet0 - Group 1

  State is Active

    37 state changes, last state change 4w1d

  Virtual IP address is 194.73.x.x

  Active virtual MAC address is 0000.0c07.xxxx

    Local virtual MAC address is 0000.0c07.xxxx (default)

  Hello time 3 sec, hold time 8 sec

    Next hello sent in 1.868 secs

  Authentication text "xxxx"

  Preemption enabled

  Active router is local

  Standby router is 194.74.x.x, priority 100 (expires in 7.868 sec)

  Priority 150 (configured 150)

    Track interface Serial0:0.1 state Up decrement 100

  IP redundancy name is "xxx" (default) FastEthernet0 - Group 2

  State is Standby

    59 state changes, last state change 3w1d

  Virtual IP address is 194.74.x.x

  Active virtual MAC address is 0000.0c07.xxxx

    Local virtual MAC address is 0000.0c07.xxxx (default)

  Hello time 3 sec, hold time 8 sec

    Next hello sent in 0.488 secs

  Authentication text "xxxx"

  Preemption enabled

  Active router is 194.74.x.x, priority 150 (expires in 6.484 sec)

  Standby router is local

  Priority 100 (default 100)

  IP redundancy name is "xxx" (default) xxxx-Pri#

FAILOVER

xxxx#sh ip int brie

Interface                  IP-Address      OK? Method Status                Protocol

FastEthernet0              194.74.x.x    YES NVRAM  up                    up     

Serial0:0                  unassigned      YES NVRAM  up                    up     

Serial0:0.1                x.x.x.x     YES NVRAM  up                    up     

#sh standby

FastEthernet0 - Group 1

  State is Standby

    42 state changes, last state change 4w1d

  Virtual IP address is 194.73.x.x

  Active virtual MAC address is 0000.0c07.xxxx

    Local virtual MAC address is 0000.0c07.xxxx (default)

  Hello time 3 sec, hold time 8 sec

    Next hello sent in 0.620 secs

  Authentication text "xxxx"

  Preemption enabled

  Active router is 194.73.x.x, priority 150 (expires in 7.628 sec)

  Standby router is local

  Priority 100 (default 100)

  IP redundancy name is "xxxx" (default) FastEthernet0 - Group 2

  State is Active

    60 state changes, last state change 3w1d

  Virtual IP address is 194.74.x.x

  Active virtual MAC address is 0000.0c07.xxxx

    Local virtual MAC address is 0000.0c07.xxxx (default)

  Hello time 3 sec, hold time 8 sec

    Next hello sent in 0.612 secs

  Authentication text "xxxx"

  Preemption enabled

  Active router is local

  Standby router is 194.73.x.x, priority 100 (expires in 6.688 sec)

  Priority 150 (configured 150)

    Track interface Serial0:0.1 state Up decrement 100

shailesh.h Fri, 04/09/2010 - 07:42

I believe you are having two subnets


1.  Subnet A - 194.73.x.x - Active router is A and standby is B

2.Subnet B - 194.74.x.x - Active router is B and standby is A


Should work from the HSRP output pasted..


With regards,


Shailesh Hardas

Laurent Aubert Fri, 04/09/2010 - 07:56

You have two HSRP groups configured one for each subnet so you should have secondary addresses configured on your interfaces.


Is it working as expected ?


Laurent.

carl_townshend Mon, 04/12/2010 - 05:35

hi


yes it seems to be...so they must have secondary addresses on there??


i gather these dont show in ip int bri command??


cheers


Carl

Correct Answer
shailesh.h Mon, 04/12/2010 - 05:39

You may use sub interface to achieve the same result... as thre are couple of limitations while particip

ating in dynamic routing protocol like OSPF.


If you are not planning to use OSPF in near future then you can continue with the configuration currently available...


Cheers!

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