/8s and filtering

Tue Dec 10 14:53:36 UTC 2002

Here is one reason for some to care :

If you want to do interdomain multicast, and your
address space is not announced globally (say because you have a /24 that 
is
not from the swamp), you are likely to be black-holed
due to RPF failures (as your unicast and multicast routing is likely to 
be different).

This has caused problems from time to time...

Regards
Marshall Eubanks

On Tuesday, December 10, 2002, at 05:58  AM, David Schwartz wrote:

>
>
>> 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. ;)
>
> 	DS
>
>
>
                                  Regards
                                  Marshall Eubanks

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