Question on Routing

Ted Mittelstaedt tedm at
Mon Jul 18 08:33:20 GMT 2005

Quagga, which is the successor to Zebra, is what you use for
BGP.  However to speak BGP you must have an AS number.  And
for your advertisements to be worth a damn on the Internet,
they have to be a minimum of a /24 since just about every
transit ISP in the Internet filters route advertisements 
that are smaller than a /24, (such as a /25, /26, etc.)

A /24 is 255 IP addresses.

Also one other thing, even if you have a /24 and you 
succeed in advertising it, it is almost impossible to get
bordering ISP's that are evenly matched.  One of them will
always be better connected than everyone else, and thus
most traffic to you will come in on that link, since everyone
routes traffic based on the shortest AS path length.

Larger ISP's that have big allocations handle this problem
by splitting up the advertisements on those allocations
into smaller blocks, then divying those up with AS prepends.

For example an ISP with a /19 might advertise it as 4 /21's,
and on one feed might prepend 2 of the /21's and not prepend
the other 2, and on another feed might prepend 1 of the /21's
and not any of the others, etc. etc.  There's a lot of experimentation
to get a load properly balanced.

I am guessing that if you don't already know that RIP isn't
a routing protocol used to publish routes on the Internet,
that you don't have much IP address space.  I think you will
find the costs to publish your routes will be an eye-opener.


>-----Original Message-----
>From: owner-freebsd-questions at
>[mailto:owner-freebsd-questions at]On Behalf Of Mark
>Sent: Saturday, July 16, 2005 8:06 PM
>To: questions at
>Subject: Question on Routing
>I'm looking for a reccomendation on the best software to 
>publish RIP routes
>for IPSpace I own.
>I'm aware I'd have to get approval from my bordering routers to 
>allow me to
>publish routes for public space, but I am just looking to 
>publish updated
>routes (dynamically) via RIP or BGP from a FreeBSD based 
>system. I've seen
>this done with gated, but at least for now I'd like to use a 
>free piece of
>freebsd-questions at mailing list
>To unsubscribe, send any mail to 
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