Failover solution using BGP

Malte von dem Hagen mvh at hosteurope.de
Wed Dec 31 01:49:04 UTC 2008


Hi,

Am 31.12.2008 01:19 Uhr, Braun, Mike schrieb:
> Why not just AS prepend your secondary site if the services to the
> Internet are the same at both sites and tied to the same IP addresses?

because that simply does not work (reliably). It would depend on
AS-paths of the same length from every possible source.

Simple, reliable and quite stylish is another way:

Choose primary and secondary location by announcing more specifics at
Sacramento, e.g. all networks as /20 subnets. As "longest match always
wins", any source seeing both routes for an IP address will choose
Sacramento.

The only way traffic could reach LA would be a missing route to
Sacramento. In any other case, Sacramento is chosen. Thus, if Sacramento
(manually or automatically) stops announcing the /20s, LA's /18 and /19
will be chosen.

CAVE:  This is no failover solution for single services, just for whole
       subnets depending on the announcement at Sacramento.

CAVE2: My suggestion creates inconsistent announcements for the source
       AS. That may or may not be a problem.

Kind regards,

Malte
-- 
Malte v. dem Hagen

Abteilung Technik - Network Operations Centre
-----------------------------------------------------------------
Host Europe GmbH            - http://www.hosteurope.de/
Welserstrasse 14            - D-51149 Köln - Germany
Telefon 0800-4 67 83 87     - Telefax 01805-66 32 33
HRB 28495 Amtsgericht Koeln - UST ID DE187370678
GF: Uwe Braun - Alex Collins - Mark Joseph - Patrick Pulvermüller
-----------------------------------------------------------------

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 257 bytes
Desc: OpenPGP digital signature
URL: <http://mailman.nanog.org/pipermail/nanog/attachments/20081231/794445cf/attachment.sig>


More information about the NANOG mailing list