nanog mailing list archives
Re: Lots of prepends - AS20912 case
From: Dorn Hetzel <dhetzel () gmail com>
Date: Fri, 20 Feb 2009 10:56:56 -0500
If we really want bgp for idiots, perhaps a checkbox for "make this (slightly,more,greatly) less preferred for incoming traffic" would do the job :) Then again, perhaps people who want the results of their local configuration distributed to the ends of the earth should at least read a book or two... -Dorn On Fri, Feb 20, 2009 at 10:35 AM, Ivan Pepelnjak <ivan.pepelnjak () zaplana net
wrote:
From the end-user perspective, it makes sense to make the "prepend"parameter an integer. The only thing an end-user really needs is routing policy (primary/backup selection) and sometimes AS path prepending is the only solution. Allowing them to insert third-party AS numbers into the AS path increases their confusion (assuming they were never exposed to Cisco IOS). Obviously, the number of prepends has to be limited to something sensible (10 seems a good number, and it looks like Mikrotik has implemented that restriction). The "set as-path prepend last-as" is a completely different story; it's used to do proxy prepending for your customers. Ivan Pepelnjak http://blog.ioshints.info-----Original Message----- From: Mikael Abrahamsson [mailto:swmike () swm pp se] Sent: Friday, February 20, 2009 3:06 PM To: nanog () nanog org Subject: Re: Lots of prepends - AS20912 case On Fri, 20 Feb 2009, Dorn Hetzel wrote:Replacing what is conventially thought to be a string withan integermultiplier seems a massive violation of the principle ofleast astonishment. On a Cisco running 12.0S: route-map test1 set as-path prepend last-as ? <1-10> number of last-AS prepends Cisco seems to be doing more sensible limits, but I do agree that the feature makes sense. There are two ways of handling when someone puts in a very high number to number of prepends: 1. Say "out of limit" and disallow it in the config checker. 2. Actually prepend the number of times specified. The option done here: 3. Prepend number of times entered modulo 256, is just broken. -- Mikael Abrahamsson email: swmike () swm pp se
Current thread:
- Lots of prepends - AS20912 case Giuliano Peritore (Feb 20)
- Re: Lots of prepends - AS20912 case Tomas Caslavsky (Feb 20)
- Re: Lots of prepends - AS20912 case Jon Lewis (Feb 20)
- Re: Lots of prepends - AS20912 case Dorn Hetzel (Feb 20)
- Re: Lots of prepends - AS20912 case Mikael Abrahamsson (Feb 20)
- Re: Lots of prepends - AS20912 case Mathias Sundman (Feb 20)
- Re: Lots of prepends - AS20912 case Dorn Hetzel (Feb 20)
- RE: Lots of prepends - AS20912 case Ivan Pepelnjak (Feb 20)
- Re: Lots of prepends - AS20912 case Dorn Hetzel (Feb 20)
- Re: Lots of prepends - AS20912 case Dorn Hetzel (Feb 20)