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RE: BGP route filtering technique order of use posted 06/05/2008
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There are several "basic" things I like to write down at the first hint of
needing to think through a problem.  If I have to do any serious subnetting, I
take the time to write out 8 bits in a row and label them /25, /26...; .128,
.192...; .127, .63....  It sounds lame, but after 5 hours of grinding you can
really drop the ball on an acl subnet mask.

The same thing applies to BGP route selection.  Odom's CCIE written study
guide has a neat little snippet on remembering the order, and the result is
the list of initials - N WLLA OMNI.  I write that list vertically on my
scratch paper, and as soon as I encounter a filtering or weighting problem I
consult the list.  There may be three ways to do something and the task only
bans one, which is actually worse for you since now you have to judge the
consequences of the remaining two.


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> Date: Thu, 5 Jun 2008 13:08:10 +0100
> From: jedidinesh@xxxxxxxxxxxxxx
> To: smorris@xxxxxxxxxxxx
> Subject: Re: BGP route filtering technique order of use
> CC: ccielab@xxxxxxxxxxxxxx
>
> many thanks Scott. That is much more systematic and helps my understanding.
>
> Dinesh
>
>
>
>
> On Thu, Jun 5, 2008 at 12:48 PM, Scott Morris <smorris@xxxxxxxxxxxx> wrote:
>
> > I think your ordering is just a touch off there...  (#3/4 of each)
> >
> >
> >
http://www.cisco.com/en/US/tech/tk365/technologies_q_and_a_item09186a0080094
> >
9e8.shtml#one<http://www.cisco.com/en/US/tech/tk365/technologies_q_and_a_item
09186a00800949e8.shtml#one>
> >
> > HTH,
> >
> >
> > Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713,
JNCIE-M
> > #153, JNCIS-ER, CISSP, et al.
> > CCSI/JNCI-M/JNCI-ER
> > VP - Technical Training - IPexpert, Inc.
> > IPexpert Sr. Technical Instructor
> >
> > smorris@xxxxxxxxxxxx
> >
> >
> >
> > Telephone: +1.810.326.1444
> > Fax: +1.810.454.0130
> > http://www.ipexpert.com
> >
> >
> >
> >
> >
> > -----Original Message-----
> > From: nobody@xxxxxxxxxxxxxx [mailto:nobody@xxxxxxxxxxxxxx] On Behalf Of
> > Dinesh Patel
> > Sent: Thursday, June 05, 2008 7:01 AM
> > To: ccielab@xxxxxxxxxxxxxx
> > Subject: BGP route filtering technique order of use
> >
> > hi group.
> >
> > I'm trying to outline the best technique to use when filtering routes in
> > BGP.
> >
> > Is the following the best order for bgp routers coming IN:
> >
> > 1) use route-map
> > 2) use filter-list for AS paths
> > 3) use distribute-list
> > 4) use prefix list
> >
> >
> > Is the following the best order for bgp routers going OUT:
> >
> >
> > 1) use distribute-list
> > 2) use prefix list
> > 3) use route-map
> > 4) use filter-list for AS paths
> >
> >
> > It would be good to know the best order so you can be consistent.
> >
> > Dinesh
> >
> >
> > _______________________________________________________________________
> > Subscription information may be found at:
> > http://www.groupstudy.com/list/CCIELab.html
>
>
> _______________________________________________________________________
> Subscription information may be found at:
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>
>
>

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