×

Warning message

  • Cisco Support Forums is in Read Only mode while the site is being migrated.
  • Cisco Support Forums is in Read Only mode while the site is being migrated.

HSRP question?

Answered Question
Feb 15th, 2014
User Badges:

I started learining CCNP swtiching

1)If we give same priority value in active and stand by device ,how redundcy will work ?

2)How Preempt works in HSRP?




Thanks in advance

Correct Answer by Kevin Dorrell about 3 years 6 months ago

100

P.S. Sorry, I didn't see Joseph's reply due to quirk of the Android app display.


Sent from Cisco Technical Support Android App

Correct Answer by Joseph W. Doherty about 3 years 6 months ago

100

Correct Answer by devdeep98 about 3 years 6 months ago

HSRP.JPG

Dear All,



            HSRP is a cisco propriotary protocol created in 1994.Uses multicast address 224.0.0.2 with UDP port 1985 to communicate with HSRP routers within the group.HSRP uses a virtual IP and virtual mac 0000.0c07.acXX where XX is the HSRP group number.Basically all the FHRP's are ment to provide Gateway redundacy for end devices.



The higher priority router will act as a Active or who has the highest physical interface IP address will be the Active,lower priority/IP address router will act as Standby.And to Take Over from lower enable "PREEMPT".Simply the HSRP group routers sends periodic Hello's after 3 seconds on multicast address 224.0.0.2 udp 1985 to check the Active router's availability and if Active goes the standby will take over ...........Here is the scoope.......what if Active router is up and running and your ISP link is down ......In that case the standby will not take over however it is configured to preempt............I am writing all configuration for the HSRP below have a look and that's it....you are done with HSRP.................... ...configure interface IP schemes on your own Ok.......



R1(config)#int f0/0

R1(config-if)#standby 10 ip 192.168.10.3

R1(config-if)#standby 10 preempt

R1(config-if)#standby 10 priority 150

R1(config-if)#standby 10 track serial 0/0 60



NOTE :-


1. The last command will decrement the actual priority of 150 by 60 which is 90.That means now standby will now take over however the R1is up.As it has now decremented priority of 90.............but the R1's serial 0/0 is down(the link to ISP cloud is down).



Once the R1's serial 0/0 interface will come up the R1 will be the active router again as the priority will become 150 again automatically.



2.You can use IP SLA as well to track the interface.


------------------------------------------------------------------------------------------------------------

R2(config)#int f0/0

R2(config-if)#standby 10 ip 192.168.10.3

R2(config-if)#standby 10 preempt

R2(config-if)#standby 10 priority 110

NOTE :- Normal configuration would be applied on R2 with "preempt enable, keep in mind"if want failover.

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (3 ratings)
Loading.
Inderjeet Singh Sat, 02/15/2014 - 01:21
User Badges:

Praveen,


If you do not give priority in HSRP than the device which comes live first or which receives configuration first will become active and the other will become standby..


the use of preempt is like, if you have two routers and R1 is active and R2 is standby.. if R1 fails than standby R2 will takeover and will become active.. but if after sometime, R1 is back, it will take priority over R2 and will become active again.. if you do not use preempt, R2 will continue to be active unless R2 reboots or fails..


I hope it would be clear.. please rate the answer if it is helpful.

Joseph W. Doherty Sat, 02/15/2014 - 03:58
User Badges:
  • Super Bronze, 10000 points or more

Disclaimer


The   Author of this posting offers the information contained within this   posting without consideration and with the reader's understanding that   there's no implied or expressed suitability or fitness for any purpose.   Information provided is for informational purposes only and should not   be construed as rendering professional advice of any kind. Usage of  this  posting's information is solely at reader's own risk.


Liability Disclaimer


In   no event shall Author be liable for any damages whatsoever (including,   without limitation, damages for loss of use, data or profit) arising  out  of the use or inability to use the posting's information even if  Author  has been advised of the possibility of such damage.


Posting


#1


If standby fails, nothing changes.  If standby recovers, nothing changes.


If active fails, standby becomes active.  If previous active recovers, it becomes standby.


#2


When a "new" HSRP member becomes active, if its priority is higher than current active, it becomes new active.

Correct Answer
devdeep98 Sat, 02/15/2014 - 04:21
User Badges:

HSRP.JPG

Dear All,



            HSRP is a cisco propriotary protocol created in 1994.Uses multicast address 224.0.0.2 with UDP port 1985 to communicate with HSRP routers within the group.HSRP uses a virtual IP and virtual mac 0000.0c07.acXX where XX is the HSRP group number.Basically all the FHRP's are ment to provide Gateway redundacy for end devices.



The higher priority router will act as a Active or who has the highest physical interface IP address will be the Active,lower priority/IP address router will act as Standby.And to Take Over from lower enable "PREEMPT".Simply the HSRP group routers sends periodic Hello's after 3 seconds on multicast address 224.0.0.2 udp 1985 to check the Active router's availability and if Active goes the standby will take over ...........Here is the scoope.......what if Active router is up and running and your ISP link is down ......In that case the standby will not take over however it is configured to preempt............I am writing all configuration for the HSRP below have a look and that's it....you are done with HSRP.................... ...configure interface IP schemes on your own Ok.......



R1(config)#int f0/0

R1(config-if)#standby 10 ip 192.168.10.3

R1(config-if)#standby 10 preempt

R1(config-if)#standby 10 priority 150

R1(config-if)#standby 10 track serial 0/0 60



NOTE :-


1. The last command will decrement the actual priority of 150 by 60 which is 90.That means now standby will now take over however the R1is up.As it has now decremented priority of 90.............but the R1's serial 0/0 is down(the link to ISP cloud is down).



Once the R1's serial 0/0 interface will come up the R1 will be the active router again as the priority will become 150 again automatically.



2.You can use IP SLA as well to track the interface.


------------------------------------------------------------------------------------------------------------

R2(config)#int f0/0

R2(config-if)#standby 10 ip 192.168.10.3

R2(config-if)#standby 10 preempt

R2(config-if)#standby 10 priority 110

NOTE :- Normal configuration would be applied on R2 with "preempt enable, keep in mind"if want failover.

praveennoc Sat, 02/15/2014 - 07:31
User Badges:

Thank you to all


What is the default priority number in HSRP

devdeep98 Wed, 02/19/2014 - 01:26
User Badges:

It is 100 but you can play with it..............the loveliest part is set priorities on your own on both routers......with tacking.

One more thing if you want to load balance through HSRP.......you can do that as well by creating two different groups of HSRP......and assign the interfaces/vlan into that ......will do the load balancing for your end system devices based on round robin method........................................But you know what I will recomend GLBP if you are using 4500 or 6500 switches.............it will do load balancing as well and you would have more load balancing methods like round robin, Host dependent and Weighted....................awesome GLBP fall in love......................


One more key information guys................On layer 3 always the Highest IP or Priority wins.................and if you talk about layer 2 Lowest Mac address wins......keep in mind always..........whatever you implement or configure............

Correct Answer
Kevin Dorrell Sat, 02/15/2014 - 23:01
User Badges:
  • Green, 3000 points or more

100

P.S. Sorry, I didn't see Joseph's reply due to quirk of the Android app display.


Sent from Cisco Technical Support Android App

Actions

This Discussion