RE: Getting a "portable" /19 or /20
From: Patrick Evans [mailto:pre@pre.org] Sent: Tuesday, April 10, 2001 10:22 AM
On the flipside, who is actually less concerned about routing table size? The multihomed networks on the edges who can use a default if they want to, and are likely to be carrying less traffic and so have more resources to deal with routing, or the core networks who have capacity problems of their own?
AFAICT, multi-homing doesn't work unless you also have dynamic routing. Is this wrong?
On Tue, 10 Apr 2001, Roeland Meyer wrote:
AFAICT, multi-homing doesn't work unless you also have dynamic routing. Is this wrong?
Well, if all you care about is redundant routes (not optimizing paths) and don't worry about asymmetric paths, you can announce just your prefixes to each upstream and use only default routes (either received via BGP or static interface routes) for outbound traffic. John A. Tamplin jat@jaet.org 770/436-5387 HOME 4116 Manson Ave 770/431-9459 FAX Smyrna, GA 30082-3723
On Tue, Apr 10, 2001 at 12:55:40PM -0500, John A. Tamplin wrote:
On Tue, 10 Apr 2001, Roeland Meyer wrote:
AFAICT, multi-homing doesn't work unless you also have dynamic routing. Is this wrong?
Well, if all you care about is redundant routes (not optimizing paths) and don't worry about asymmetric paths, you can announce just your prefixes to each upstream and use only default routes (either received via BGP or static interface routes) for outbound traffic.
"announce" presupposes dynamic routing, doesn't it? You can multi-home with everything routed statically, as long as you have unsophisiticated requirements for choosing an outbound path, don't need transport session stability, and can cope with some of your addresses being unreachable from the rest of the network when one of your providers stops being able to reach you. Doing things this way can also make network problems harder to debug. I multi-home like this at home, between a cheap DSL provider and a cheap cable-modem supplier. So far there hasn't been a time when both providers went down simultaneously. I have protected myself from around forty-eight aggregate hours of downtime over the past four months, and I haven't had to waste any time on the phone to the cable operator helpdesk explaining to them the benefits of running BGP to me. I could have bought a pair of T1s to different providers and run BGP; however, this would probably cost me around $3000 per month more than I'm currently paying, would give me half the performance, and would require me to buy a router with WAN interfaces (instead of the OpenBSD box with 3 x $10 NICs). Oh, and my multi-homing doesn't contribute to state bloat in the DFZ :) Joe
participants (3)
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Joe Abley -
John A. Tamplin -
Roeland Meyer