From: W. Alan Robertson (warobertson@earthlink.net)
Date: Mon Nov 10 2003 - 12:25:10 GMT-3
As Jason pointed out, you can advertize a host route (/32) with BGP if you
want to. Mask length restrictions are not a technical limitation of BGP,
but rather, they are a policy limitation imposed by the ISPs.
For all intents and purposes, if you want to run BGP and have your routes
carried globally, you need a legitimate class-C address space, a /24.
Your directly connected upstream neighbors may accept smaller routes than
that, but most likely, anything smaller than a /24 will not be advertized
outside your upstream neighbors. They'll either filter it out themselves on
their outbound advertisments, or their peers will filter them on receiving
them.
The reason is that if routes for these smallish subnets were accepted by
everyone, then an allready huge global routing table would balloon out of
control, melting the world's routers down to smoldering piles of slag
(Perhaps an overstatement, but a colorful one!). The memory requiements for
carrying a full BGP routing table would be tremendous if every little subnet
were carried.
Alan
----- Original Message -----
From: <wing_lam@jossynergy.com>
To: <ccielab@groupstudy.com>
Sent: Monday, November 10, 2003 2:50 AM
Subject: longest subnetmask can route in Internet
> Hi,
>
> Any body can tell me what is the longest subnetmask that can be routed in
> Internet (BGP)? I planned to advertise a route with /29 but don't know
> whether this can be achieved. Is there any restriction about that?
>
> I can see /27 routes now in BGP.
>
> Thx,
> BBD
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