nanog mailing list archives
Re: BGP 011: multiple sessions with upstreams
From: Joe Abley <jabley () isc org>
Date: Sat, 1 Jan 2005 11:19:15 -0500
On 31 Dec 2004, at 11:01, Edward B. Dreger wrote:
I'm trying to persuade them that two provider/customer BGP sessions is agood thing,
The obvious reason for this might be explained along the lines of "your router can reach two of our routers. We'd like a BGP session to each so that we can take our routers down for maintenance when we feel like it, without causing routes to be withdrawn". If this doesn't gel with their policy, and you care about it, find a new ISP (but see below).
and NEXT_HOP set to the HSRP-managed IP address would allow them to steer customer traffic.
I've made efforts to set this kind of thing up before (not at ISC), and in hindsight I wish I hadn't bothered. It was an unconventional configuration from the provider's perspective that was not preserved across provider router upgrades and configuration cleanups, and it opened us up to yet another failure mode (that of HSRP breakage, which is most definitely not unknown on many releases of IOS).
If you suffer unplanned outages so often that HSRP is going to make a noticeable difference, then it's probably a good idea to deal with whatever is causing the unplanned outages (unreliable telco, squirrels chewing through cables, poorly-sized UPSes, crimp-happy PBX monkeys).
If you're trying to protect against planned outages, then gracefully admin-downing the BGP sessions on the router which has impending maintenance (leaving BGP sessions to other router(s) up and running) might accomplish the same graceful failover that you're trying to use HSRP for.
Their argument is that one can "get extra bandwidth" with two BGP sessions, and that HSRP prevents that. I've pointed out that equal-cost multipath BGP is far from default behavior, and that one can "get extra bandwidth" even without two BGP sessions.
An extra BGP session will not magically give you more bandwidth. An extra circuit will not-so-magically give you more bandwidth, although often not as much as you think.
Am I missing something?
For your provider, supporting pur-laine, standard-configuration customers is cheaper than supporting customers where each has their own special-case setup. Supporting a network of routers where the protocols and configuration is consistent is also easier (and hence cheaper) than a network where each router has special, exciting new config bits found nowhere else.
Your choices may be:1. Pay a premium to deal with an ISP who can really afford to support special-case customers;
2. Pay a cheaper price, and deal with reduced support and spontaneous mystery outages as engineers not familiar with your particular arrangement make general changes to their network;
3. Accept the standard setup, pay a cheaper price and get reasonable support.
Joe
Current thread:
- Re: BGP 011: multiple sessions with upstreams Christopher L. Morrow (Dec 31)
- <Possible follow-ups>
- Re: BGP 011: multiple sessions with upstreams Joe Abley (Jan 01)
- Re: BGP 011: multiple sessions with upstreams Christopher L. Morrow (Jan 01)
- Re: BGP 011: multiple sessions with upstreams Edward B. Dreger (Jan 02)
- Re: BGP 011: multiple sessions with upstreams Steve Gibbard (Jan 03)
- Re: BGP 011: multiple sessions with upstreams Christopher L. Morrow (Jan 01)