Re: how to reduce HSRP delay?

anand · ‎12-13-2005

Hi,

I have got 2 Nos. of 3550-12T & 1 2950T for testing, below are the configuration for 3550. created vl 2, 3, 4 & 5.

3550T-Main config.

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vlan 2

ip address 192.168.10.253 255.255.255.0

standby 2 ip 192.168.10.252

standby 2 timers 5 15

standby 2 priority 109

standby 2 preempt

3550T-Standby config.

vlan 2

ip address 192.168.10.254 255.255.255.0

standby 2 ip 192.168.10.252

standby 2 timers 5 15

standby 2 priority 110

standby 2 preempt

like this on all vlan interface with diff. IP & diff. group ID

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between 2 3550's i have made trunking & on 2950T 1 port is connected to Main 3550 & other to Standby 3550. on 2950T i hav connected 3 diff PC & all 3 are in 3 different vlan's. now when i switch off Main 3550 or disconnect the uplink cable which goes to 2950T, it takes 30 sec to reach the other vlan pc. so how do i reduce the time for less than 10 sec.

Georg Pauwen · ‎12-13-2005

Hello Anand,

with your current configuration, the failover should occur in 15 seconds (3 missed hello´s, which equal 15 seconds). The lowest configurable value is:

standby 1 timers msec 15 msec 50

You might want to try and configure these and see if it makes a difference.

Your problem might also be related to spanning tree convergence, you might want to set the forward-delay and max-age timers for your VLANs to the lowest possible values:

spanning-tree vlan 2 forward-time 4

spanning-tree vlan 2 max-age 6

Can you try this and see if it makes a difference ?

HTH,

GP

anand · ‎12-13-2005

Hi gpauwen,

i tried the 1st option which you have mentioned, with that also there is no difference, only this is the port started blinking very fast apart from that no changes in that, also you told me try that "spanning-tree vlan 2 forward-time 4 & spanning-tree vlan 2 max-age 6" but on which interface should i need to put this command? waiting for your reply. do i need to put it on trunking interface? if so should put those commands on both the side i mean 3550 & 2950?

m.mcconnell · ‎12-13-2005

The spanning-tree commands are done in global configuration mode. This is because the spanning Tree Protocol runs per VLAN, not per interface. HSRP can only failover AFTER STP reconverges.

Additionally, you will also want to set the hello time as low as possible.

spanning-tree vlan 2 hello-time 1

This has significant control over STP reconvergence times. With the STP timers set this low you will get fast reconvergence times ~10secs. I usually set these timers for all VLANs - on all switches.

You also want to watch your STP diameter with the timers this low. It is not recommended to stack/daisy-chain switches more than 2 deep from the core giving a maximum STP diameter of 3.

-Mark

m.mcconnell · ‎12-13-2005