[NANOG] Routing table for BGP

Joe Greco jgreco at ns.sol.net
Fri May 16 14:34:15 UTC 2008


> Hi,
> 
> I would like to know what route should i accept from internet full or
> partial?
> if Partial then what routes should i accept? and how many route does my
> router have if i will go for Partial routing table?
> 
> actually I am trying to understand it by concept... my organization is small
> but I want to know if it is large organization or small provider then what
> kind of routes do i need in my routing table?

If you don't know, then you should probably ask your upstream to send you
a default and leave it at that.

Full routes means that you get a routing entry for every network connected
to the Internet.  There's some two hundred thousand (plus) of them.  This 
can be stressful on both routers and inexperienced administrators, and is
probably not all that useful unless you have multiple connections to the
Internet.  A default gets you just about the same thing.

"Partial" doesn't make too much sense, unless you really don't want to
talk to certain parts of the Internet, or you're supplementing it with a
default route.  You could potentially do this if you had, for example, a
T1 to two different providers, and wanted some outgoing traffic to go
over each link.

In that case, most people would prefer to get full tables from each
upstream and make local decisions.  This requires properly resourcing
your router; the "Cidr Report" that is frequently posted here will give
you an idea about /current/ requirements in terms of table size, but it
is not unreasonable to look for something that can handle 30-50% growth,
plus IPv6 concerns.

If you've got an existing router that can't hack it, but still need to
balance over two connections, that's one scenario for "partial" routes.
By definition, partial would be any number between 1 and the current 
number of available route prefixes, and would be determined by your choice
of configurations.

There are some really quite excellent books on routing on the Internet
available, as well as extensive information in this list's archive.  Avi
also has some historical documents that are probably still good.  Look
around

http://www.freedman.net/

... JG
-- 
Joe Greco - sol.net Network Services - Milwaukee, WI - http://www.sol.net
"We call it the 'one bite at the apple' rule. Give me one chance [and] then I
won't contact you again." - Direct Marketing Ass'n position on e-mail spam(CNN)
With 24 million small businesses in the US alone, that's way too many apples.




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