From: Howard C. Berkowitz (hcb@gettcomm.com)
Date: Tue May 11 2004 - 17:52:52 GMT-3
At 3:47 PM -0400 5/11/04, MMoniz wrote:
>Richard, I wouldn't take that to mean that you should be able to look up
>everything and be able to pass.
>
>But some things are just not going to come into play in the lab. Knowing how
>to find things will.
>
>Just like this topic. So you spend time trying to remember exactly the BGP
>route selection process.
>Then you get to the lab and they say something like rtr x should prefer this
>route without using
>As path, BGP router id , med or local pref.
It's probably not one of those things where you should ask the
proctor "should I do this the IETF way or the Cisco way," because RFC
1771 does _not_ include AS_PATH as a decision factor. It is worth
knowing there is a Cisco knob to turn off considering it.
In practice, AS_PATH is the most important selector, and is part of
the algorithm in the new BGP standard draft.
Other gotchas are that there's a Cisco way and an IETF way, with a
knob to select the non-default IETF behavior, on how to compare two
routes, one with a MED and one without. Of course, this gets further
complicated with the sometimes very useful Cisco option
always-compare-MED (at least, it's very useful in ISP operations at
an exchange point). Once you start using MEDs, I can't think of any
good reason not to enable BGP deterministic-MED, which, IMNSHO,
should be the default.
>Since these things are so
>jumbled in the selction process
>chances are you are going to have to look this up any how. Thus you just
>wasted, well in my case, precious
>brain cell space on something that you no longer need to rememeber.
I could probably tell you the preference based on ORIGIN, but I don't
think I've ever seen a real-world case where that actually became a
decision factor. (And a voice says, "and what relevance does your
real-world experience have to the lab?"
>
>Unless you have a photographic memory, or at least a bunch of unused brain
>cells to store this info, you are much
>better off knowing the core stuff and KNOWING where to find things on the
>doc CD/site that are a little abstract.
>
>Just my opinion,
>
>Mike
>
>
>
>
>
>-----Original Message-----
>From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
>Richard Dumoulin
>Sent: Tuesday, May 11, 2004 3:30 PM
>To: Andaluz, Danilo; swm@emanon.com; ccielab@groupstudy.com
>Subject: RE: BGP route selection
>
>
>Ok, but then everything is on the doc-cd ...
>
>-----Original Message-----
>From: Andaluz, Danilo [mailto:danny.andaluz@hp.com]
>Sent: martes, 11 de mayo de 2004 20:10
>To: swm@emanon.com; Richard Dumoulin; ccielab@groupstudy.com
>Subject: RE: BGP route selection
>
>
>I agree. Why remember it if it is out on the CD already?
>
>Danny
>
>-----Original Message-----
>From: Scott Morris [mailto:swm@emanon.com]
>Sent: Tuesday, May 11, 2004 1:26 PM
>To: 'Richard Dumoulin'; Andaluz, Danilo; ccielab@groupstudy.com
>Subject: RE: BGP route selection
>
>If you know where to look it up swiftly, you don't need ot know it by heart.
>
>There are too many things out there to try to memorize everything. Know the
>important things, don't sweat the details, but know how to find them!
>
>
>Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, CISSP,
>JNCIP, et al. IPExpert CCIE Program Manager IPExpert Sr. Technical
>Instructor swm@emanon.com/smorris@ipexpert.net
>http://www.ipexpert.net
>
>
>
>-----Original Message-----
>From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
>Richard Dumoulin
>Sent: Tuesday, May 11, 2004 1:15 PM
>To: Andaluz, Danilo; ccielab@groupstudy.com
>Subject: RE: BGP route selection
>
>Thx Danilo but I said "remember". How do you remember it ? By heart ?
>
>-----Original Message-----
>From: Andaluz, Danilo [mailto:danny.andaluz@hp.com]
>Sent: martes, 11 de mayo de 2004 19:09
>To: Richard Dumoulin; ccielab@groupstudy.com
>Subject: RE: BGP route selection
>
>
>
>http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/
>fipr_c/ipcprt2/1cfbgp.htm#wp1000898
>
>Danny
>
>
>-----Original Message-----
>From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
>Richard Dumoulin
>Sent: Tuesday, May 11, 2004 12:59 PM
>To: ccielab@groupstudy.com
>Subject: BGP route selection
>
>Hello group,
>
> I am interested in how do you guys remember the bgp route slection
>algorythm ? Have you read so much BGP that it comes naturally ?
>
>Thank you
>
>--Richard
>
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