SP / Enterprise design (dis)similarities

Tom Lanyon tom+nanog at oneshoeco.com
Mon Oct 10 22:42:14 UTC 2011

Hi all,

Looking for some advice or experience in a small enterprise / hosting provider context.

There's plenty of BCP information around for SPs in the network design realm, and I'm curious how much of this applies to enterprises too.  Commonly advised items like:
	* pull-up statics created on core devices, not network border devices
	* using iBGP to carry customer prefixes, not an IGP
	* announcing defaults over iBGP or IGP

In some cases I imagine it may be simpler to have all BGP finish at the network border devices and not have to worry about running both IGP and iBGP sessions inwards to the core and/or aggregation devices.  I understand the limitations of putting our Internet prefixes in an IGP, but for a hosting provider style network where everything is ethernet connected and within data centres there's much less route flapping to deal with (there's no bouncing DSL lines, for example).

In the case that there is both iBGP and IGP running internally, is there any reason to choose one or the other to originate a default route to our aggregation/access layers?  At some point I imagine it's going to be redistributed into the IGP (or re-originated in the IGP), so would think it would be best to just always run the default in the IGP to keep things consistent.

Finally - are there any reasons to avoid running next-hop-self on ibgp sessions?  The upside is we get to avoid distributing all of our transit/peer upstream point to point links into the rest of the network.  Again, I understand this may be undesirable from a SP perspective, but when our 'clients' are all a bunch of internal servers it makes sense to keep iBGP/IGP as clean as possible...


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