/8s and filtering

David Schwartz davids at webmaster.com
Tue Dec 10 10:58:18 UTC 2002

>I was also curious about this - if I am a customer who wants to
>multihome and can justify only a /24, I would go to an ISP
>which has an allocation from the Class C space rather than one from the
>Class A space.

	It doesn't matter. For all practical purposes, basement multihomers only 
care that their two or three providers have their route.

> Do ISPs get to choose where the allocation comes from?

	Ask your ISP if they'll let you choose. But it usually doesn't matter, if 
you can only justify a /24, you'll find about the same filtering policies in 
both traditional class A space and class C space.

	But again, it doesn't matter. So long as each of your providers will honor 
your route (and why wouldn't they, you're paying them to)  you shouldn't have 
a problem.

	Just pick your most reliable provider, and the one you're pretty sure you're 
going to stay with the longest, and get your IP space from them. Make sure 
they don't mind you advertising your block through other providers.

	And give some thought to hiring a competent consultant to help you. You can 
hire a consultant even if you are the consultant. In fact, no competent 
consultant would do otherwise outside his or her area of expertise. Don't 
learn to multihome at your client's expense. ;)


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