/19 addresses and redundancy

Jay Stewart cosmo at olywa.net
Wed Nov 5 18:07:46 UTC 1997

> Greetings,
> Here is a question -- maybe someone out there can suggest a solution to a
> problem...
> We are a small to mid-sized ISP and we feel that in order to compete in
> todays market we need to provide multiple circuits to different backbone
> providers and run BGP.  We currently have a single T1 (from Sprintlink) 
> which is handling our leased line, web, and dialup customers with little
> trouble (running at about 20-25%).  We want to add another T1 to another
> major carrier so we can offer a backup circuit in the event our T1 goes
> down or if Sprint has a major outage.  Of course, this wouldn't be just
> for backup -- it would share the load... 
> We currently have 15 class C addresses and we have been told by Sprint
> that anthing smaller than a /19 BGP may get filtered.  Since we have a
> whole bunch of non-contiguous class C address (which Sprint gave us), it
> seems that BGP would never work.
> So, we contacted the Internic and requested a /19 block so we can do this. 
> The Internic refuses to give someone a /19 block unless they are in need
> of it right away (a few months projections).  We don't need 32 Class Cs
> because we need to assign that many but we need them because we want to be
> able to use BGP.  The Internic will not give them to us and we seem to
> have no options. 
> Are there ways around this?

Ignore dire warnings, multi-home and run BGP4 anyway, I think you'll
find that your routes are heard by the large majority of sites.  By 
the time it really matters, you'll be able to justify a /19.

We are doing this exact thing, (main T1 to sprint, another T1 to 
second provider, publishing routes via BGP and excepting two full 
routing views of the net), and have had little trouble with it.

Jay Stewart
Vice President
Olympia Networking Services - "Olympia's Premier Internet Provider"
Phone 360.753-3636  Fax 360.357.6160  http://www.olywa.net/

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