It's important to think about what we consider to be failures in our ISP
and then ask the question: "What are we protecting ourselves from?" In
our case, more often than not an outage is caused by downtime on our
directly connected router or a failure on the physical link itself,
between the CO and our building.
In both of those cases, redundant links to different locations of the
same provider would give us a reasonable level of assurance. Unless
there is an ISP-wide failure of some sort, you shouldn't have much of a
problem. These are known to occur from time to time but I don't think
they're very common, especially if you choose a reputable provider.
We're have two Sprint circuits at the moment and are tentatively
planning for a third. I've been very happy with them so far.
I'd imagine that any large ISP like Sprint, Cable & Wireless, AT&T,
UUnet, or Global Crossing would be able to provide this type of service
for a reasonable fee. This would eliminate the hassle of trying to get
a /24 *and* an AS number from ARIN, and it most likely would resolve the
issues you have.
John
>>> "Daniel Wilson" 7/6/01 3:16:59 PM >>>
Thank you for the response, John.
Accessibility from just about anywhere, especially in the US, keeps me
happy
too. But our ISPs have a tendency to mess up routing table entries or
otherwise shut us off. We have outgrown a single T1, and want to add
some
redundancy.
I need a solution that will mean that a *single* mistake outside of
our
control doesn't shut us down. There's an ISP in town that's willing to
run
BGP with us -- and they want us to get both lines from them. But would
that
put us back into the position of being vulnerable to a single mistake
at
their location? If *both* our ISPs mess up at the same time -- well,
that's
exceptionally bad luck. I realize we have to accept some risk for
things
that are so unlikely. But yesterday morning, one ISP was down for 45
minutes, taking down most of our sites. This afternoon the other one
is
down, taking down one of our newest clients.
You're right we don't quite need a /24 ... /25 or probably even /26
would
work. And the ISP in town wants to set us up on one of their private
ASN's.
They're also trying to talk us out of running BGP, though they'll do it
if
we insist.
If an ISP -- either our current one or another one -- can provide us
circuits that follow different paths, would that give us the level of
redundancy we're looking for?
Thanks again!
--
Daniel Wilson
""John Neiberger"" wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> Keep in mind what is actually occurring when using BGP. You are
> advertising prefixes from your AS into your provider's AS. They in
turn
> either include your specific prefix in their announcements to other
> providers, or they aggregate your smaller prefix into larger
> advertisements. It is at this stage that you need to worry about
what
> other providers are doing as far as filtering.
>
> If your provider is advertising your specific prefix, a /24 for
> instance, but the other companies won't accept anything less than a
/22,
> then you're up a creek. We are advertising a /24 to two separate
> providers and I haven't seen any reachability problems from anywhere
in
> the world. As far as I'm concerned, if we can be reached by either
path
> from just about anywhere, especially in the US, then I'm happy.
>
> I've been following your posts and I'm curious about your motivation
> for adding a second provider. This adds a measure of complexity
that
> might not be necessary, depending on your goals. Can your current
> provider give you a circuit that follows a separate path then your
first
> circuit? If so, that would eliminate a couple of issues.
>
> First, you wouldn't even necessarily need to run BGP, although I
would
> prefer to do so. But instead of getting full routes, you could
accept
> defaults-only from your provider and advertise your addresses on
both
> links.
>
> Second, you wouldn't worry about getting an entire /24--or
> larger--block of addresses. In this scenario, your provider will
> aggregate your prefix into their larger announcements, but when
traffic
> destined for your network arrives in their network, internally
they'll
> see two available paths. This has the additional benefit of not
wasting
> registered addresses since you probably don't really need an entire
> /24.
>
> Third, you won't have to apply for your own AS number from Arin.
If
> you run BGP over two links to the same provider, they will either
let
> you use their ASN or let you use a private ASN that will only be seen
by
> their network.
>
> Would a solution like this work for you?
>
> Regards,
> John
>
> ----------------------------------------------------------
> John Neiberger
> Firstbank Data Corporation
> 12345 W. Colfax Ave.
> Lakewood, CO 80215
> (303) 235-1093
>
>
> >>> "Daniel Wilson" 7/6/01 12:23:46 PM >>>
> We are looking into multi-homing our network and running BGP on our
> router.
>
> I was told by some of you before that some ISPs won't advertise a
block
> of
> IP's smaller than /22 and many won't do any smaller than /24. That
> leads to
> this question.
>
> Are our ISPs the only ones that need to advertise our block? Or
does
> everybody out there need to advertise the block?
>
> Thanks!
>
> --
> Daniel Wilson
> CompuSoft Solutions and The Worthwhile Company
> http://www.worthwhile.com
> Your complete e-business solution partners.
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