Re: OT : BGP soft-reconfiguration inbound memory costs

Thanks for your replies. My copy of BGP design and implementation is in the
mail :) The chapter on BGP memory use estimation sounds quite interesting.

Fabian : This is what I used as a basis for my labbing. Maybe I'm not
monitoring the right counters which would explain why I can't see the
difference in memory usage.

Max : I think this configuration was added by one of my predecessors to be
able to run "show ip bgp neighbor x.x.x.x received-routes". You mentioned
that you could indeed notice that memory usage increased. Which show
commands/OID did you use to measure this difference?

Regards,

Eric

On Sun, Feb 27, 2011 at 3:16 AM, Max Pierson <nmaxpierson_at_gmail.com> wrote:

> >Does anybody have any experience with this feature?
>
> On 12.4.x (something mainline I believe) I do. It does take up memory on a
> 720xVXR router with a NPE-G1 thats noticeable.
>
> As Fabian was alluding to, it's only necessary when testing filters now
> that BGP supports route-refresh so you don't have to keep a state table.
> There's no other reason I can think of where you would need to apply it, so
> I only use it on peers if I need to test filters.
>
>
> -
> m
>
>
> On Sat, Feb 26, 2011 at 4:39 PM, eric_at_linux.ca <eric.lauriault_at_gmail.com>wrote:
>
>> This is precisely what I thought too. I had 3 peers with full feed
>> configured with the soft-reconfig inboud command. I figured I'd save on
>> ram
>> by removing it but couldn't see any difference afterwards...
>>
>> Full feeds were on 12.2(33)SXI. I labbed it up under 12.4(15)T.
>>
>> Does anybody have any experience with this feature?
>>
>> Eric
>>
>> On Sat, Feb 26, 2011 at 4:03 PM, Fabian Pucciarelli <fabiangp_at_gmail.com
>> >wrote:
>>
>> > My understanding is that when you enable the feature you need enough RAM
>> to
>> > hold 2x the amount of nlri received from that neighbor. If you receive
>> > internet full tables you would require a lot of memory, if it is a small
>> > table you don't require much. I only use the feature to be able to use
>> show
>> > ip bgp neighbor x received and compare it to show ip bgp neighbor x
>> routes
>> > when testing inbound filters.
>> >
>> > F.
>> > On Feb 25, 2011 2:22 PM, "eric_at_linux.ca" <eric.lauriault_at_gmail.com>
>> wrote:
>> > > Hi all,
>> > >
>> > > For a long time, word on the street was that "soft-reconfig inbound"
>> > takes
>> > > quite a bit of memory and is not as useful as it once was since most
>> BGP
>> > > implementations have added route refresh capabilities. I've also read
>> > that
>> > > "the code has been optimized and that the memory impact is
>> insignificant
>> > > nowdays". Kinda contradictory. I can't seem to find much information
>> on
>> > the
>> > > exact cost in memory of this feature.
>> > >
>> > > For some time, we had this feature enabled on a few peers with full
>> > feeds.
>> > > One would think that by removing it, we would save quite a bit of ram.
>> We
>> > > didn't see any quantifiable difference in RAM usage.
>> > >
>> > > I've tried measuring the exact cost of this feature in a lab
>> environment
>> > but
>> > > the following show commands weren't very helpful :
>> > >
>> > > show proc mem | i BGP : the bgp processes seem to take the exact same
>> > amount
>> > > of RAM
>> > > show ip bgp sum : the memory and path/bestpath fields seems to be
>> exactly
>> > > the same, whether the command is there or not
>> > > show ip bgp neigh : can't find anything there either
>> > >
>> > > Does anybody have any clear understanding of the memory costs of the
>> > > "soft-reconfiguration inbound" command?
>> > >
>> > > Regards,
>> > >
>> > > Eric Lauriault, #27521
>> > >
>> > >
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>> > >
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Received on Sun Feb 27 2011 - 17:45:27 ART