Solved: Re: HSRP Stanby Time

Anand Narayana · ‎12-19-2005

Hi,

I have 3550 2 Nos. & 2950T 1 No. Created 3 Vlans, vlan 2-4, below are the configurations for Main & Standby Switches

spanning-tree vlan 2-4 hello-time 1

spanning-tree vlan 2-4 forward-time 4

spanning-tree vlan 2-4 max-age 6

Vlan 2(Main)

ip address 192.168.10.253 255.255.255.0

standby 2 ip 192.168.10.252

standby 2 ip priority 109

standby 2 ip timers 5 15

standby 2 preempt

Vlan 3(Main)

ip address 192.168.11.253 255.255.255.0

standby 3 ip 192.168.11.252

standby 3 ip priority 109

standby 3 ip timers 5 15

standby 3 preempt

Vlan 4(Main)

ip address 192.168.12.253 255.255.255.0

standby 4 ip 192.168.12.252

standby 4 ip priority 109

standby 4 ip timers 5 15

standby 4 preempt

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

spanning-tree vlan 2-4 hello-time 1

spanning-tree vlan 2-4 forward-time 4

spanning-tree vlan 2-4 max-age 6

Vlan 2(Standby)

ip address 192.168.10.254 255.255.255.0

standby 2 ip 192.168.10.252

standby 2 ip priority 110

standby 2 ip timers 5 15

standby 2 preempt

Vlan 3(Standby)

ip address 192.168.11.254 255.255.255.0

standby 3 ip 192.168.11.252

standby 3 ip priority 110

standby 3 ip timers 5 15

standby 3 preempt

Vlan 4(Standby)

ip address 192.168.12.254 255.255.255.0

standby 4 ip 192.168.12.252

standby 4 ip priority 110

standby 4 ip timers 5 15

standby 4 preempt

From 2950T switch, 1 port is connected to Main & Other port is connected to Standby Switch configued trunking. Between Main & Standby Switch cable is connected configured Trunking. 2 Client PC's which are in 2 different Vlan's are connected in 2950T. Now if i disconnect or Switch OFF the Main switch, it is taking less than 10 seconds to reach the other Vlan PC, which is normal. now when do in reverse, i mean if i disconnect or Switch OFF the standby switch there is no effect, it is keep on pinging continious (there is no request timed out). why is that so? & why not it is happening the same in Main switch?

amit-singh · ‎12-20-2005

Hi Anand,

Pls see the post above by Rick. he has already explained the exact behaviour that you will see in your case. Just to highlight that again, When your main switch i.e the ACTIVE HSRP router goes down you will have the service disruption till the hold time vlaue 15 seconds in your case.This is the time that HSRP will take to go through diff states and eventually declaring standby router as active router.

Now,if you power-off your secondry switch which is already secondry for HSRP,you will not see any service disruption as your active router whihc is your gateway for client is still active.You will see service disrupption only when it goes from active to secondry.

More-over your STP root is the active router, that's why you also saw that behaviour. It is always recommended that make your STP rooot bridge as the active router and your secondry root bridge as the standby for all the vlans.This way it will work as expected and with less service disruption.

regards,

-amit singh

View solution in original post

Georg Pauwen · ‎12-19-2005

Hello Anand,

can you check which one of the switches is the root ?

Regards,

GP

Anand Narayana · ‎12-19-2005

How do i check that? both the main & standby switches are having the same config, except the Priority value & the IP address changes,

Georg Pauwen · ‎12-19-2005

Hello,

you can check which one is the root with the command:

show spanning-tree vlan 2

The output of the root bridge will say ´we are are root´.

The reason I am asking is that your ´problem´, or observation, might be related to the fact that the main switch is the root, and that therefore the failover is shorter, because there is no STP convergence...

Regards,

GP

Richard Burts · ‎12-19-2005

I am not sure that I accurately understand the description given by Anand. But I think he is describing a situation where he has PC(s) in one VLAN and PC(s) in another VLAN and is pinging between them as he disables and enables the primary and backup switch.

If my understanding is correct then the behavior that he describes is the correct behavior as I understand it. The first thing to remember is that traffic from one VLAN to the other VLAN must go to the default gateway and the default gateway should be the HSRP address. Therefore if he is pinging with both switche active and switches off the main switch, then there should be some interruption in the ping while HSRP recognizes the failure and gives the HSRP address to the backup switch. However if he is pinging with both switches active and switches off the backup switch there should be no interruption to the ping since the primary switch already has the HSRP address and does not have to change anything.

If my understanding of the situation is faulty please clarify what is going on.

HTH

Rick

HTH

Rick

Anand Narayana · ‎12-19-2005

Hi GP,

i checked, the Main switch is the root stating "This bridge is the root" so how do i proceed now? my requirement is even if one of the switch goes down, i should not get 10 sec of time delay on the network, because currently what happens is only if main switches goes down i get 10 seconds, where in if the standby switches goes down, i am getting any delay.

amit-singh · ‎12-20-2005