[20453] in North American Network Operators' Group
Re: IGPs in use
daemon@ATHENA.MIT.EDU (Tony Li)
Tue Oct 13 18:31:51 1998
To: hcb@clark.net (Howard C. Berkowitz)
CC: nanog@merit.edu
From: Tony Li <tli@juniper.net>
Date: 13 Oct 1998 15:18:00 -0700
In-Reply-To: hcb@clark.net's message of 13 Oct 98 14:01:07 GMT
hcb@clark.net (Howard C. Berkowitz) writes:
> When I gave my OSPF tutorial at NANOG in June, I stressed OSPF shouldn't be
> thought of purely as a 2-level hierarchy with a routing domain consisting
> of an area 0 and a set of nonzero areas. Some of the OSPF scaling
> problems I see, and these are probably equally likely in IS-IS, come from
> people trying to put everything into a single OSPF routing domain. Aside
> from performance issues, this can become a network administration nightmare.
>
> Splitting the interior network into several IGP routing domains, and
> linking these with a backbone-of-backbones, helps both performance and
> administration. The backbone group doesn't need to be concerned with LAN
> installations in a POP or customer site. Depending on the particular
> network, you might link IGP routing domains with:
>
> -- static routes
> -- iBGP, putting all IGPs in a single AS
> -- iBGP and eBGP in a confederation
> -- Hybrid layer 2/3 techniques, such as linking IGP-routed domains
> to internal layer 2 "superhubs"
>
> How much IGP support you need will depend on your network. A large
> enterprise, or a provider of both connectivity and content, will probably
> need more IGP stuff than a pure connectivity provider.
Howard,
Yes, those sound like a list of administrative nightmares. ;-)
Wouldn't it be much easier to make use of a three or four level
hierarchical IGP?
Tony
