[189086] in North American Network Operators' Group
Re: BGP peering strategies for smaller routers
daemon@ATHENA.MIT.EDU (=?utf-8?Q?=C5=81ukasz_Bromirski?=)
Tue May 3 17:14:13 2016
X-Original-To: nanog@nanog.org
From: =?utf-8?Q?=C5=81ukasz_Bromirski?= <lukasz@bromirski.net>
In-Reply-To: <CAP-guGXJR5BFsF4a4c1VZsTn4L72au3K3XiEESzpfAF8BSZsYQ@mail.gmail.com>
Date: Tue, 3 May 2016 23:13:11 +0200
To: William Herrin <bill@herrin.us>
Cc: NANOG list <nanog@nanog.org>
Errors-To: nanog-bounces@nanog.org
> On 03 May 2016, at 22:31, William Herrin <bill@herrin.us> wrote:
>=20
> On Tue, May 3, 2016 at 3:50 PM, Gustav Ulander
> <gustav.ulander@telecomputing.se> wrote:
>> Yes I can confirm that we also had the issue with the asr1001s.
>> For us the router was fine until we upgraded it. When
>> we rebooted it after the upgrade it ran out of memory
>> when populating 2 full feeds.
>> When we contacted TAC they confirmed that indeed
>> it was a memory problem and that we would need to
>> add more memory to the box.
>=20
> Hi Gustav,
>=20
> IMO, you should not accept that answer from the TAC. An IOS release
> that crashes with two 600k BGP feeds in 4 gigs of RAM is badly
> defective.
Not necessarily.
In essence, your physical memory gets halved in two after
router boots up, then it may be further halved if you=E2=80=99re
using features like SSO. So, with 4GB RAM config and with
SSO running, you may be left with around 600-650MB free after
boot and with IOS-XE loaded, and then all the features kick
in. Including your BGP feeds that need around 300MB of memory
just to store the tables, then there=E2=80=99s CEF RAM representation,
and so on.
Here=E2=80=99s a good WP w/r to memory usage & architecture on ASR 1k:
=
http://www.cisco.com/c/en/us/support/docs/routers/asr-1000-series-aggregat=
ion-services-routers/116777-technote-product-00.html
It actually contains the same recommendation given by TAC -
with recent/current code if you want to run full tables with
BGP, get 8GB of RAM on ASR 1k. In the 3.10-3.12S era I believe
it was still possible to fit (without the SSO) full tables
in RAM and be fine.=20
As Nick just responded, it=E2=80=99s faster to source the RAM or modify
the config to cut down on number of BGP prefixes rather than
ping back and forth here discussing all the possibilities.
--=20
=C5=81ukasz Bromirski
CCIE R&S/SP #15929, CCDE #2012::17, PGP Key ID: 0xFD077F6A
