Re: BGP inbound/outbound filter preference

Thanks Tyson, great explanation!

Cheers.

On Wed, Nov 3, 2010 at 3:42 PM, Tyson Scott <tscott_at_ipexpert.com> wrote:

> Emir,
>
> It is important to understand the logic because all can be applied to the
> same neighbor statements. Because it is logic that you need to understand
> it could always be a question on a lab or the actual exam. As an example
>
> Let's say for one task you are asked to control inbound prefix's using
> prefix lists. Then later another task asks you to attach communities to a
> network that you filtered with your prefix list. If you were not aware of
> this logic you wouldn't realize that the previous task needs to be appended
> to include the additional prefix that you need to add to your prefix list
> and make sure your last route-map statement is a permit as the route-map is
> not being used as your filtering policy.
>
> Regards,
>
> Tyson Scott - CCIE #13513 R&S, Security, and SP
> Managing Partner / Sr. Instructor - IPexpert, Inc.
> Mailto: tscott_at_ipexpert.com
> Telephone: +1.810.326.1444, ext. 208
> Live Assistance, Please visit: www.ipexpert.com/chat
> eFax: +1.810.454.0130
>
> IPexpert is a premier provider of Self-Study Workbooks, Video on Demand,
> Audio Tools, Online Hardware Rental and Classroom Training for the Cisco
> CCIE (R&S, Voice, Security & Service Provider) certification(s) with
> training locations throughout the United States, Europe, South Asia and
> Australia. Be sure to visit our online communities at
> www.ipexpert.com/communities and our public website at www.ipexpert.com
>
>
> -----Original Message-----
> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
> emir
> d souza
> Sent: Tuesday, November 02, 2010 5:54 PM
> To: alexeim73_at_gmail.com
> Cc: Cisco certification
> Subject: Re: BGP inbound/outbound filter preference
>
> Hi Alex,
>
> Yup, that's true, but why then would we need the prefix list in the same
> config if the route-map is good enough to do everything else. I've seen
> this
> config on some SP routers, but fail to understand the logic of having both
> inbound.
>
> neighbor yadayada route-map CISCO in
> neighbor yadayada prefix-list CISCO in
>
> Does anyone know?
>
> Cheers.
>
> On Tue, Nov 2, 2010 at 6:52 PM, Alexei Monastyrnyi
> <alexeim73_at_gmail.com>wrote:
>
> > Hi.
> >
> > With route-map you can match things other than prefixes, and also
> > manipulate attributes. Also with route-maps you can impose more
> > sophisticated logic upon your peers.
> >
> > HTH
> > A.
> >
> > On 11/2/2010 9:45 AM, emir d souza wrote:
> >
> > Hi Guys,
> >
> > I'm a bit confused, from what I understand is that for filtering traffic,
> > BGP will look at filtering in this order:-
> >
> > Inbound: route-map > filter-list > prefix-list
> > Outbound: prefix-list > filter-list > route-map
> >
> > Question is: For example. why bother having both route-map and
> prefix-list
> > filtering on the inbound when you can just use a single route-map to
> filter
> > in traffic. I've seen this being done on some SP routers, and I'm
> wondering
> > if there good explanation as to why they are doing this.
> >
> > Route-map will filter out community tags and prefix-list will filter out
> > specific routes, can't we do both on route-maps alone??
> >
> > Cheers.
> >
> > Emir
> >
> >
> > Blogs and organic groups at http://www.ccie.net
> >
> > _______________________________________________________________________
> > Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
>
>
> Blogs and organic groups at http://www.ccie.net
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html

Blogs and organic groups at http://www.ccie.net
Received on Wed Nov 03 2010 - 22:28:22 ART