Hi Marshall If a route isnt withdrawn when the end network/device fails then no system will fix that. Presumably anycast wouldnt enable load balancing anyway as BGP only installs a single route? Or are you thinking both of these would be solved with a BGP enhancement? Dont understand the multiple anycast comment, do you mean as it stands now? If so it works fine if you inject the same route into an IGP providing you ensure theres no IGP load balancing if you intend on doing TCP (altho most applications for this appear to be UDP single request-responses) Steve On Fri, 5 Jul 2002, Marshall Eubanks wrote:
On Fri, 5 Jul 2002 13:36:49 +0100 (BST) "Stephen J. Wilcox" <steve@opaltelecom.co.uk> wrote:
Doesnt announcing the same routing prefix into BGP from multiple locations do the same thing without needing a new range or enhancement in IGMP etc ?
We do this in IGP currently..
Steve
As I see it, the problems with doing this in BGP are
- it's static - no failover. If AS 701 and AS 1239 are both announcing a route to foo, and your preferred route is "through" AS701, and the AS701 foo goes down, then you do not automatically switch over to the AS1239 foo, even if you could reach it.
- there is no way to have multiple anycast addresses within an AS
- load balancing is tough
These may all be solved, though... it's hard to tell without a protocol description.
Regards Marshall Eubanks
On Fri, 5 Jul 2002, Barry Raveendran Greene wrote:
FYI - for those scratching their heads on "anycast" .....
I just pushed out a paper on anycast by Chris Metz. Good foundation material.
http://www.cisco.com/public/cons/isp/essentials/ip-anycast-cmetz-03.pdf
-----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu]On Behalf Of Bill Woodcock Sent: Friday, July 05, 2002 4:56 AM To: Marshall Eubanks Cc: nanog@merit.edu Subject: Re: Internet vulnerabilities
> But the only IPv4 anycast > that I know of does use MSDP : > http://www.ietf.org/internet-drafts/draft-ietf-mboned-anycast-rp-08.txt > Is there a different proposal ? What's the RFC / I-D name ?
You seem to be confusing anycast with something complicated. It's not a protocol, it's a method of assigning and routing addresses.
-Bill