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HSRP delay minimum & reload question

HiTmAn47
Beginner
Beginner

Hello , 

 

Iam a little confused about the reason for the delay minimum and reload benefits ,

 

I mean If I added 60 secs minimum delay or 60 secs reload delay  ,

 

Iam basically telling my standby router to not take over until after 60 secs ....so that means 60 secs of network outage 

 

Why would I need that ? why would I need 60 secs either after an outage or after a reboot ?

 

also I would appreciate if someone shed some light of the usefulness of minimum and reload as Iam a little confused about the two 

1 Accepted Solution

Accepted Solutions

Hi

The preempt delay means that, when the interface gets up it will detect that there is already an hsrp neighbour active. Thus, that active router will continue forward traffic, and this router will wait for configured time until it takes over the role.

If we don't wait, we will take over the active role immediate and that can be a problem if routing is not yet ready.

Also, if the other router is not detected, this router will take the active role immediate, and do not wait the configured time, and starts forward traffic as soon as routing is ready.

/Mikael

View solution in original post

6 Replies 6

Reza Sharifi
Hall of Fame Master Hall of Fame Master
Hall of Fame Master

Hi,

Here is the explanation from the config guide:

standby delay minimum min-seconds reload

(Optional) Configures the delay period before the initialization of HSRP groups. • The min-seconds value is the minimum time (in seconds) to delay HSRP group initialization after an interface comes up. This minimum delay period applies to all subsequent interface events. • The reload-seconds value is the time period to delay after the router has reloaded. This delay period applies only to the first interface-up event after the router has reloaded.

link for more info:

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipapp_fhrp/configuration/12-2sr/fhp-12-2sr-book/fhp-hsrp.pdf

HTH

Still it didn't answer my main question ...

why I will want to do this ? this will delay my convergence time and keep my network dead until the delay time is over 

Philip D'Ath
Advisor
Advisor

Lets say you have a bunch of routing protocols, and you know it takes them 30s to re-converge.  If the HSRP router became active before this it would cause an outage.  So you delay becoming active until you know the router has had enough time to get itself into a proper working state.

 

Other examples are interfaces that can take a long time to come up from cold, like 3G.

But if the backup is not active then the whole network will be cut from the internet still ... 

so you are cutting off the backup for 30 secs in order not to have an outage for 30 secs !!

that doesn't make sense to me  

Hi

The preempt delay means that, when the interface gets up it will detect that there is already an hsrp neighbour active. Thus, that active router will continue forward traffic, and this router will wait for configured time until it takes over the role.

If we don't wait, we will take over the active role immediate and that can be a problem if routing is not yet ready.

Also, if the other router is not detected, this router will take the active role immediate, and do not wait the configured time, and starts forward traffic as soon as routing is ready.

/Mikael

Hi An47,

 

Sorry to drop by just now. To comment on your question,  it really does not make sense to configure the HSRP delay minimum/reload commands on a standby device as it will defeat the purpose of HSRP. But it make sense to configure it on the active device. To explain further;

 

Normal Network condition based on as-built Networ design/setup:

 

1. R1 act as Active Router (Forwarding traffic)

2. R2 act as Standby Router (Currently not forwarding traffic but is ready to forward traffic)

 

Network Issue occured:

 

1. R1 uplink to Internet goes down or

2. R1 rebooted 

 

For both issues, R2 with preemption configured, should immediately take over the role of active router and forward traffic.                           

 

Aside from the preemption, R1 should also be configured with the HSRP delay minimum/reload command so that when the uplink to Internet goes up or while the device is completing the reload process, it will wait for everything to normalize (as mentioned in the post/replies) before attempting/forcing to REgain the role of Active Router.

 

 

 

 

 

 

 

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