North American Network Operators Group

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Re: FW: /8s and filtering

  • From: bmanning
  • Date: Tue Dec 10 15:13:50 2002

> Hello,
>  No, this is not the case. I enquired and it seems multihoming is not a
> justification for a /24 in any RIR.
>  Does a network have to be able to fully utilize a /26 (25% of /24) in
> order to multihome?
> Harsha.

	You do err, not knowing the scripture.

	To multihome, you need to get (at least) two other providers to listen
	to your routing announcement(s).  Wango'z'tango! multihoming done.
	Your announcement can be as small as a /32 (although there was a
	time when at least one /33 was delegated...)
	What's that?  you want everyone running IP to reach your gopher
	server?  Tough luck.  then you must somehow meet/pass the  
	byzantine filtering rules (unpublished sometimes) that parties 
	which are three and four hops away from your edge will impose on 
	whatever announcements you happen to propogate.  The dead hand of 
	the CIDR mafia will eat your lunch and you'll have no recourse.

	So, whats a poor'lil player todo?  Some say that this works:

		) build a rich peering mesh. (reduces your dependence
		  on any one transit provider)
		) buy transit (where you -MUST-) and insist that you
	  	  understand BGP, peering, and how to prevent leakage.
		  Demand that they accept your announcement(s). 
		  [ note that this may turn transit into peering, which
		    may trigger other unpleasent SOPs from the salesdroids
		    but hey, multihoming is -worth- the effort...]

	as usual, YMMV.

--bill (who is earning the sobriquet "grumpy" today)