>On Tue, 25 Jul 2000 [EMAIL PROTECTED] wrote:
>
> > I trying to add redundency to my network at work (I work for a very small
> > local ISP) and I'd like to run BGP on this router so that if line A dies to
> > upstream provider A, line B will take over to upstream provider B.
> >
> > What is the least requirement for BGP? Someone told me I needed at least a
> > /20 of IP's from ARIN. Someone else told me that I need SWIP instead of
> > RWHOIS. So I'm left wondering exactly what is the minimum overall
> > requirements to run BGP?
>
>There is none. You can be single homed and run BGP (But why do that?).
Depends on what you mean by multihomed. It can be quite reasonable
to run BGP when you are connected to multiple POPs of a single
provider, and want to optimize the way your provider sends you
traffic at multiple points. See RFC1998 for this application of the
well-known community of NO-EXPORT.
>
>Basically anytime you are multihomed, and the goal is transit for your
>customers, then I would say you want to run BGP. Will your upstreams
>filter something you have less than a /20? Probably not. Alot of ISP's
>are allocated a /24, /23, or /22 at a time........so maybe the largest
>contigious block that have is a /22.
>
>Redundancy is a cinch with BGP. If you are announcing all your netblocks
>to both your upstreams, then you have incoming redundancy. If you are
>taking full routes from both upstreams, or a combination of full routes
>and or partial routes w/default, then you have the outgoing redundancy.
Was it the Athenians or the Spartans that said to the Laconians, "If
we defeat you, we will burn your city to the ground, enslave the
survivors, and salt the ruins?"
To which King Lacon responded, "If."
In this case, if your providers do announce netblocks in a useful
way. Useful walks the thin line between what is good for their
customer and what is good for the global routing system.
There are still reasons to limit the size of the global routing
table, although the reasons have changed over time. The first
generations of reasons were based on the 16 MB RAM of the AGS+. The
second generation of reasons were processor rather than memory
limited, principally by the 68040 in the 7000. Current reasons
include the raw time to propagate the routing updates, route
stability, and convergence times.
Incidentally, there are multiple useful definitions of convergence
time. I'm working on a paper on this to be submitted to the IETF
Benchmarking Technology Working Group.
>
>Using a little tuning is needed, prepending AS and fiddiling around with
>various knobs until you get the balance just right.
I wouldn't call it that simple. You can prepend AS and twiddle MED,
local pref, etc., all you want, but if, for example, your primary
upstream doesn't advertise your more specific route and your
secondary does, it's entirely possible that all of your outgoing
traffic will go out the primary and return through the secondary.
Internet routing has a lot of coordination aspects and isn't just
tuning your BGP knobs,
>
> >
> > Maybe I don't need BGP? Maybe a floating static route might also
>work? Please
> > explain and give sample code if possible.
>
>You are paying both providers to take your traffic, so make them work for
>their money. Run BGP and make sure all your netblocks can go across
>either provider.
>
>Who are your upstreams?
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