Jay thank you for that, it cleared a misconception I had. I thought
portfast only affected the port in question when it came online, as
when you plugged it in. I didn't realize that it would impact an
indirect re-convergence. I tested it and it worked just like you said,
I drop one packet.
I am doing both ether-channel and HSRP on the uplinks. I'm thinking
more about what happens if I lose one of my redundant core switches.
Also my IDF's are setup as a ring or stacked topology because I don't
have enough fiber to uplink each switch. So in a situation where I
lose the middle switch in a stack I would be relying on spanning-tree
re-converging.
One other thing I am still unclear about is that the max-age still
shows 20 seconds, in the output. Isn't it supposed to be 3 x hello?
Bah, I probably just need to re-watch the STP videos.
Cat1#show span
VLAN0001
Spanning tree enabled protocol rstp
Root ID Priority 24577
Address 5475.d029.7080
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 24577 (priority 24576 sys-id-ext 1)
Address 5475.d029.7080
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300
On Wed, Mar 9, 2011 at 7:50 PM, [email protected] <[email protected]> wrote:
> Well if yor timers are that bad for VOIP you can always use hsrp if you
> don't want to use the etherchannel option. You can tune hsrp down to
> milliseconds if you wanted to. Of course your distribution switches need to
> support an enhanced IOS image
>
> Sent from my Verizon Wireless Phone
>
> ----- Reply message -----
> From: "Jay Taylor" <[email protected]>
> Date: Wed, Mar 9, 2011 7:57 pm
> Subject: [OSL | CCIE_RS] Rapid Spanning Tree convergence times
> To: "marc abel" <[email protected]>
> Cc: <[email protected]>
>
>
> Enable portfast on the host ports and you'll see a much quicker transition.
> Just labbed this up and with portfast enabled I lost a single ping during
> the failover. Without it enabled I lost 12.
>
> For the VoIP question - in production I'd recommend building with
> Etherchannels just so STP never needs to converge.
>
>
> On Wed, Mar 9, 2011 at 5:41 PM, marc abel <[email protected]> wrote:
>
>> I have 4 switches connected in a loop.
>>
>> Cat1-------------Cat2
>> | |
>> | |
>> Cat3----------Cat4
>>
>>
>> Cat 1 is the root, Cat 2 is the secondary root. All the switches are
>> set to RPVSTP and I have confirmed that show spanning-tree shows RSTP
>> as the protocol. Cat 4 shows it's interface to cat3 as it's root port
>> and the interface to Cat3 as the Alternate. I have not tuned any
>> timers.
>>
>> What should be the convergence time in this situation?
>>
>> If I run a ping from a host attached to Cat4 to a host attached to
>> Cat1 and then I shut the Cat1-Cat3 interface (on the Cat1 side) it
>> takes about 32 seconds before pings pick back up. I thought RSTP was
>> supposed to converge in about 6 seconds?
>>
>> Another question, what is the fastest recovery time we can tune down
>> to from RSTP? How do others tune this for VOIP? I know that I can get
>> sub second convergence from OSPF but not all my switches have an
>> appropriate image to run ospf.
>>
>>
>> Thanks in advance.
>>
>> Marc
>> _______________________________________________
>> For more information regarding industry leading CCIE Lab training, please
>> visit www.ipexpert.com
>>
> _______________________________________________
> For more information regarding industry leading CCIE Lab training, please
> visit www.ipexpert.com
>
>
>
>
_______________________________________________
For more information regarding industry leading CCIE Lab training, please visit
www.ipexpert.com
