[117578] in North American Network Operators' Group
Re: Multi-POP design check/help question
daemon@ATHENA.MIT.EDU (Truman Boyes)
Mon Sep 21 00:35:29 2009
From: Truman Boyes <truman@suspicious.org>
In-Reply-To: <01B071CE08A7514CB72950074134151AE288F4@STNTEXCH12.cis.neustar.com>
Date: Mon, 21 Sep 2009 14:34:33 +1000
To: "Fouant, Stefan" <Stefan.Fouant@neustar.biz>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On 21/09/2009, at 7:37 AM, Fouant, Stefan wrote:
> I don't know if you want to arbitrarily use local-pref and AS-Path =20
> prepend in a one-size-fits-all approach, as under certain scenarios =20=
> it might be more beneficial to route traffic between POPs to take =20
> advantage of routes via shortest AS Path or other constraints. Why =20=
> not just extend your IGP across all POPs and set inter-POP links to =20=
> a higher metric? In this scenario, if a given route is received via =20=
> muliple POPs and all things being equal (AS Path, etc.), you'll =20
> prefer to route traffic out the shortest-cost path to a POP exit =20
> point.
>
> Sorry for the top post, I'm on my BB.
>
> Stefan Fouant
> Neustar, Inc. / Principal Engineer
> 46000 Center Oak Plaza Sterling, VA 20166
> Office: +1.571.434.5656 =E2=96=AB Mobile: +1.202.210.2075 =E2=96=AB =
GPG ID: =20
> 0xB5E3803D =E2=96=AB stefan.fouant@neustar.biz
>
I agree with Stefan. You are better off extending your IGP across PoPs =20=
as it will give you more flexibility in the long run. If you ever want =20=
to go down the path of traffic engineering / MPLS / etc, you will find =20=
it much easier as this will allow for CSPF and multi-topology routing =20=
architectures.
Truman
> ----- Original Message -----
> From: Rick Ernst <nanog@shreddedmail.com>
> To: nanog@nanog.org <nanog@nanog.org>
> Sent: Sun Sep 20 16:17:41 2009
> Subject: Multi-POP design check/help question
>
> Cross-posted from cisco-nsp. We are a (mostly) Cisco shop, but I'm =20=
> looking
> more for BCP and overall design, not provisioning specifics.
>
>
> -----
>
> My Cisco bookshelf isn't helping me much with this...
>
> We currently have a single POP with border/core/aggregation topology.
> Upstreams each come in on their own border router and the core is =20
> used as a
> route-reflector for border and aggregation. The internal network =20
> uses OSPF
> as an IGP and each device is dual-connected for redundancy on =20
> independent
> layer-2 networks. OSPF load-shares with loopback IPs and IBGP uses =20=
> the
> loopback addresses for peering.
>
> We are looking at turning up two additional POPs in the metro area, =20=
> each
> connected by redundant GigE loops to the original POP. Each POP may =20=
> have
> zero or more direct upstream connections. I'd like local traffic at =20=
> each
> POP to prefer both in and outbound traffic via the local upstream, =20
> but still
> be able to failover to upstreams at other POPs if needed.
>
> My initial thoughts are to BGP peer between POPs with a higher local-=20=
> pref
> for the local outbound traffic and to prepend between the POPs so =20
> inbound
> traffic is more likely to take the shortest path inbound.
>
>
> Is this too simplistic? Prone to trouble? What gotchas should I be =20
> looking
> at, or other designs should I be considering?
