OSPF vs IS-IS vs PrivateAS eBGP

Daniel Roesen dr at cluenet.de
Fri Aug 21 14:24:20 CDT 2009

On Thu, Aug 20, 2009 at 07:56:14PM -0500, Clue Store wrote:
> Most of my staff are still under the impression in Cisco land that the
> "network" statement injects than network into OSPF,
> when it simply turns on OSPF for the interfaces that are in that network.

So most of your staff is FAR away from understanding OSPF. Don't you
think it's easier to teach them BGP? Where you have a straight-forward
config of explicit neighborship, with explicit in/out prefix-lists to
control route propagation from/to customers? Where signalling channel
(BGP TCP session) is totally separated from what routing information
is being exchanged (BGP NLRI)?

OSPF just _looks_ simple when used in fully-trusted, most simple almost
all defaults config, and even then it's misleading (see your reference
to IOS' "network" statement for OSPFv2). When traffic engineering is
needed with multiple redundant uplinks for customers, things become very
interesting very quickly. Troubleshooting OSPF LSA flooding and database
replication is really HARD compared to BGP's simple UPDATE/WITHDRAW
messaging. And then you got the whole lot of different LSA types,
flooding rules, extension hacks, area types, yadda yadda. IS-IS more
straight-forward than OSPF, but still complex.

All this is referring to your concern about being able to teach the Ops
folks BGP, compared to teaching them OSPF.

In my experience, it was never a problem to teach Ops folks BGP to CPEs
(even with traffic engineering mods via route-maps), but very hard to get
them up to speed on IGPs - and I'm by no means an expert in those either.

BGP gives you more control, and with far higher chance of Ops folks
being able to troubleshoot issues to success. To me, a clear winner, if
your CPE hardware supports it.

My 0.02EUR ;)

Best regards,

CLUE-RIPE -- Jabber: dr at cluenet.de -- dr at IRCnet -- PGP: 0xA85C8AA0

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