Re: MikroTik strikes again ?
On Monday 03 May 2010 11:25:45 Bret Clark wrote: > Uhmokay...but why does anyone prepend their ASN that much? Are you > saying the Mikrotik did that on purpose? > There was a well-known routing incident last year in which a difference between the Mikrotik and Cisco CLIs caused the propagation of extremely long AS-PATH attributes, which caused certain Cisco routers to crash. Basically, someone remembered their Cisco IOS syntax and typed "bgp-prepend 47868" into a Mikrotik; the correct syntax would have been "bgp-prepend x 47868" where x is an integer between 0 and 16 representing the desired number of prepends. The Mikrotik correctly tried to prepend 47868 47868 times, but had only one byte to store this value and therefore produced 255 prepends. Some Cisco machines, it turned out, had a bug that caused path lengths close to 255 to crash them. Fun and games ensued. The Renesys blog has much, much more: http://www.renesys.com/blog/2009/02/longer-is-not-better.shtml -- The only thing worse than e-mail disclaimers...is people who send e-mail to lists complaining about them signature.asc Description: This is a digitally signed message part.
Re: MikroTik strikes again ?
Tim Warnock wrote: Adrian M wrote: MikroTik strikes again ? %BGP-6-ASPATH: Long AS path ... 39412 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 From: Bret Clark [mailto:bcl...@spectraaccess.com] Sent: Monday, 3 May 2010 8:26 PM To: nanog@nanog.org Subject: Re: MikroTik strikes again ? Uhmokay...but why does anyone prepend their ASN that much? Are you saying the Mikrotik did that on purpose? MikroTik asks for an amount of prepends rather than what ASN to prepend with. There was a bug in an old version that would modulus the ASN with 256 and prepend that many times. In this case 39625 modulo 256 = 201 prepends. Yeah...guess I see why that would be a problem.
Re: MikroTik strikes again ?
It's not really a bug, only a matter of habbit I guess :) I read this some time ago in nanog list: http://www.renesys.com/blog/2009/02/longer-is-not-better.shtml regards, Christian Bret Clark wrote: Uhmokay...but why does anyone prepend their ASN that much? Are you saying the Mikrotik did that on purpose? Adrian M wrote: MikroTik strikes again ? %BGP-6-ASPATH: Long AS path ... 39412 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 received from : More than configured MAXAS-LIMIT aut-num: AS39625 as-name: ARANEO-AS descr: Omni-Araneo's AS number org: ORG-OSTW3-RIPE import: from AS12968 action pref=100; accept ANY export: to AS12968 announce AS39625 import: from AS39412 action pref=100; accept ANY export: to AS39412 announce AS39625 admin-c: TW1273-RIPE tech-c: TW1273-RIPE mnt-by: AS12968-MNT mnt-routes: AS12968-MNT source: RIPE # Filtered
RE: MikroTik strikes again ?
> Adrian M wrote: > > MikroTik strikes again ? > > > > %BGP-6-ASPATH: Long AS path ... 39412 39625 39625 39625 39625 39625 > > 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 > > From: Bret Clark [mailto:bcl...@spectraaccess.com] > Sent: Monday, 3 May 2010 8:26 PM > To: nanog@nanog.org > Subject: Re: MikroTik strikes again ? > > Uhmokay...but why does anyone prepend their ASN that much? Are you > saying the Mikrotik did that on purpose? > MikroTik asks for an amount of prepends rather than what ASN to prepend with. There was a bug in an old version that would modulus the ASN with 256 and prepend that many times. In this case 39625 modulo 256 = 201 prepends.
Re: MikroTik strikes again ?
Uhmokay...but why does anyone prepend their ASN that much? Are you saying the Mikrotik did that on purpose? Adrian M wrote: MikroTik strikes again ? %BGP-6-ASPATH: Long AS path ... 39412 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 39625 received from : More than configured MAXAS-LIMIT aut-num: AS39625 as-name: ARANEO-AS descr: Omni-Araneo's AS number org: ORG-OSTW3-RIPE import: from AS12968 action pref=100; accept ANY export: to AS12968 announce AS39625 import: from AS39412 action pref=100; accept ANY export: to AS39412 announce AS39625 admin-c: TW1273-RIPE tech-c: TW1273-RIPE mnt-by: AS12968-MNT mnt-routes: AS12968-MNT source: RIPE # Filtered
