11-08-2012 05:48 AM - edited 03-07-2019 09:56 AM
Hi,
i have a confusion regaridng hsrp. is the config below correct?
Core 1
interface Vlan 100
ip address 10.10.10.2
no ip redirects
no ip unreachables
no ip proxy-arp
ip flow ingress
ip route-cache policy
standby 1 priority 100 (default)
standby 1 ip 10.10.10.1
standby 1 preempt
Core 2 ---- primary
interface Vlan 100
ip address 10.10.10.3
no ip redirects
no ip unreachables
no ip proxy-arp
ip flow ingress
ip route-cache policy
standby 1 ip 10.10.10.1
standby 1 priority 105
standby 1 preempt
I read on cisco website the priority being 110 (Active) and 100 (standby) - i thought it should be 105 and 100 as the decrement value is 10 - am i correct ?
Thanks
Solved! Go to Solution.
11-08-2012 06:38 AM
HI ,
yes you are right .
It should be 105.
http://en.wikipedia.org/wiki/Hot_Standby_Router_Protocol
Regards
Please rate if it helps.
11-08-2012 07:04 AM
That is correct, without tracking configured, the standby will become the active link upon an active link failure regardless of the values.
11-08-2012 05:55 AM
Hi ,
Here is the sample config for HSRP:
CORE1
interface Vlan10
ip address 10.10.10.1 255.255.255.0
standby 1 ip 10.10.10.10
standby 1 priority 150
standby 1 preempt
standby 2 ip 10.10.10.20
standby 2 preempt
end
CORE2
interface Vlan10
ip address 10.10.10.2 255.255.255.0
standby 1 ip 10.10.10.10
standby 1 preempt
standby 2 ip 10.10.10.20
standby 2 priority 150
standby 2 preempt
end
u can check the status by
CORE1#sh stand
CORE2#sh stand
follow this link ....u will find the solution:
http://journey2ccie.blogspot.de/2010/05/hsrp-on-svi-vlan-interface.html
Regards
Please rate if it helps.
11-08-2012 06:15 AM
I believe you are tracking correctly.
http://www.cisco.com/en/US/tech/tk648/tk362/technologies_tech_note09186a0080094e8c.shtml
The above link covers a scenario similar to yours. I think that the bottom line is to ensure you have a value that will ensure the standby takes over as a primary HSRP link once the primary has detected a link failure.
11-08-2012 06:26 AM
hi
thanks for youre replies...i am not tracking..i know preempt is not needed if you are not tracking but just got it in case.
i am confused by the priority values...(should the active be 105 or 110 or 120 if the standby priority is 100) - without tracking command does it decrement automatically ?
11-08-2012 06:38 AM
HI ,
yes you are right .
It should be 105.
http://en.wikipedia.org/wiki/Hot_Standby_Router_Protocol
Regards
Please rate if it helps.
11-08-2012 06:49 AM
ok i think i figured out the answer.
If we use the tracking command then we need decrement value (Default 10). so if active is 105 and standby is default (100) then if we use traccking command with a default decrement of 10 then active will go to 95 (105-10) thus the standby will be 100 which is higher than 95 so this will be active
but if we dont use tracking then i think we can use 105 or 110 or 120 or more for active router and standby as 100 or less because in this case we are not tracking so no decrement value...the standby will take over only if active router fails or crashes or if the hsrp address is not pingable then no matter what the value is the standby is, it will take over because the primary has failed.
is my thoery right ?
11-08-2012 06:55 AM
You are right,
Assigning priority helps select the active and standby routers. If preemption is enabled, the router with the highest priority becomes the designated active router. If priorities are equal, the primary IP addresses are compared, and the higher IP address has priority.
http://www.ciscozine.com/2008/11/01/how-to-optimize-hsrp/
he HSRP prefers the router with higher priority and, if it is equal, it prefers the highter IP address.
so even if you will not mention the proirity in backyp swicth , it will work perfectly.
Configure tracking, authentication, and timers on the primary router using the following commands:
- standby group_number authentication character_string
This command establishes authentication messages to be included in the HSRP multicast. This ensures that only authorized routers can become part of the HSRP group. The string must match all routers in the HSRP group.
Regards
11-08-2012 06:48 AM
Preemption enables the HSRP router with the highest priority to immediately become the active router.
Priority is determined first by the configured priority value, and then by the IP address. In case of ties,
the primary IP addresses are compared, and the higher IP address has priority. In each case, a higher
value is of greater priority. If you do not use the standby preempt interface configuration command in
the configuration for a router, that router will not become the active router, even if its priority is higher
than all other routers.
A standby router with equal priority but a higher IP address will not preempt the active router.
When a router first comes up, it does not have a complete routing table. You can set a preemption delay
that allows preemption to be delayed for a configurable time period. This delay period allows the router
to populate its routing table before becoming the active router.
If preemption is not enabled, then a router may appear to preempt the active router if it does not receive
any Hello messages from the active router.
Using 110 or 105 will work. However using 105 will ensure that when the deduction of '10' takes place, the new value will be 95, this will ensure that the standby configuration will be a higher(lower) priority value and take over as the primary link.
11-08-2012 06:59 AM
yes but without using hte tracking command does hsrp automatcially decrement by 10? i dont htink this will be the case because hsrp decrements by 10 or whatever value configured only when tracking command is used, isnt it ?
so with out tracking command i think it does not matter what value you use 110 or 120 because the standby will be active only if the primary (ex-active) crashes or if the link fails
let me know if i am wrong ?
11-08-2012 07:04 AM
That is correct, without tracking configured, the standby will become the active link upon an active link failure regardless of the values.
11-08-2012 08:28 AM
thanks :)
11-08-2012 11:01 AM
Dont forget to rate this post and marked the question as answered.
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