From: Bill Greenwood (billgreenwood@xxxxxxxxxxxxx)
Date: Thu Mar 28 2002 - 00:22:26 GMT-3
Remember the rules that must be met in order for BGP to advertise a route:
The "rule" of synchronization must be met AND if the path specifies a next
hop that is inaccessible, drop the update path specifies a next hop that is
inaccessible, drop the update.
----- Original Message -----
From: "ying chang" <ying_c@hotmail.com>
To: <WILLIAMSG@PANASONIC.COM>; <mpopovich@layer3.biz>; <meganac@attbi.com>;
<greggm@sbcglobal.net>; <ccielab@groupstudy.com>
Sent: Wednesday, March 27, 2002 9:36 PM
Subject: RE: BGP Reg Expressions
> Hi,
>
> ip as-path access-list 1 permit (64118|64239) should be fine as well.
>
> Chang
>
> >From: "Williams, Glenn" <WILLIAMSG@PANASONIC.COM>
> >Reply-To: "Williams, Glenn" <WILLIAMSG@PANASONIC.COM>
> >To: "'Michael C. Popovich '" <mpopovich@layer3.biz>, "'D. J. Jones
> >'" <meganac@attbi.com>, "'Gregg Malcolm '"
<greggm@sbcglobal.net>,
> > "'ccielab@groupstudy.com '" <ccielab@groupstudy.com>
> >Subject: RE: BGP Reg Expressions
> >Date: Wed, 27 Mar 2002 18:45:50 -0500
> >
> >FWIW, if perhaps on the lab they said use one statement to filter only AS
> >64118 to 64239 how would you do it? What I have played with that seems
to
> >work would be something like:
> >
> >ip as-path access-list 1 permit (64[1-2][1-3]9)
> >
> >If I don't have this just right, someone let me know.
> >GW
> >
> >
> >-----Original Message-----
> >From: Michael C. Popovich
> >To: D. J. Jones; Gregg Malcolm; ccielab@groupstudy.com
> >Sent: 3/27/02 6:30 PM
> >Subject: RE: BGP Reg Expressions
> >
> >I would agree with that statement.
> >
> >MP
> >
> >-----Original Message-----
> >From: D. J. Jones [mailto:meganac@attbi.com]
> >Sent: Wednesday, March 27, 2002 3:53 PM
> >To: Gregg Malcolm; ccielab@groupstudy.com
> >Subject: Re: BGP Reg Expressions
> >
> >Let me insert the whole command for completeness:
> >
> >ip as-path access-list 1 deny _150_
> >
> >dj
> >----- Original Message -----
> >From: "Gregg Malcolm" <greggm@sbcglobal.net>
> >To: <ccielab@groupstudy.com>
> >Sent: Wednesday, March 27, 2002 1:01 PM
> >Subject: Fw: BGP Reg Expressions
> >
> >
> > > > Thanks Clay. Think the light is finally getting somewhat brighter
> >for
> >me.
> > > > I set up a bunch of AS prepends on a router then played with
> >filtering
> >AS
> > > > paths.
> > > >
> > > > From what I can see, there are a few important reg exp's to remember
> >: _
> >^
> > > > and $
> > > >
> > > > _ matches any instance. Good for filtering transit AS info.
> > > > ^ matches the beginning. Used for filtering paths beginning with an
> >AS
> > > > number
> > > > $ matches ends with. Used for filtering paths that end with an AS
> >number.
> > > > I find I must use _ then path then $ (eg _30$) to filter path that
> > > > originated at path 30.
> > > >
> > > > I think these 3 along with .* and ^$ will hopefully get me thru the
> >lab.
> > > I
> > > > believe that I can do any filtering with multiples of these. Let's
> >say
> > > that
> > > > I was asked to deny all routes that originated in path 50 and all
> >routes
> > > > that passed thru 150 :
> > > > ip as-path access-list 1 deny _50$
> > > > ip as-path access-list 1 deny _150 (same as just 150 tho.. I need to
> >test
> > > > some more)
> > > > ip as-path access-list 1 permit .*
> > > >
> > > > Sound right ? I'm certain that other expressions are very useful but
> >I'm
> > > not
> > > > sure that I can remember them all. Plus, I'm not really sure that
> >they
> > > will
> > > > be needed on the lab test.
> > > >
> > > > I've also found that sh ip bgp reg <expression> helps a bunch to
> >test
> >the
> > > > expression before placing it in an as-path list. A great feature
> >that I
> > > > never really used before.
> > > >
> > > > Gregg
> > > >
> > > >
> > > >
> > > > ----- Original Message -----
> > > > From: "Clay Maney" <clay@openworldinc.com>
> > > > To: "Gregg Malcolm" <greggm@sbcglobal.net>
> > > > Sent: Wednesday, March 27, 2002 11:09 AM
> > > > Subject: Re: BGP Reg Expressions
> > > >
> > > >
> > > > > I'm not the guru here by any measure, but I can tell you this for
> >sure:
> > > > >
> > > > > the ^ means "beginning with" and the $ means "ending with".
> > > > >
> > > > > so, ^30 means "where 30 is the first AS in the list", etc.
> > > > >
> > > > > hope that helps (and please let me know if I'm wrong)
> > > > >
> > > > > Clay
> > > > >
> > > > > On Wed, Mar 27, 2002 at 10:44:35AM -0800, Gregg Malcolm wrote:
> > > > > > Folks,
> > > > > >
> > > > > > Does anyone have any good tips to help to remember reg
> >expressions ?
> > > > > > Unfortunately, my Unix background is pretty weak. I can
> >remember
> >some
> > > > of the
> > > > > > simple stuff like .* is all paths, ^$ is local routes (empty),
> >_30_
> >is
> > > > routes
> > > > > > that passed thru path 30 , etc.
> > > > > >
> > > > > > The CD is very limited with info regarding this. Best CD info
> >I've
> > > > found is
> > > > > > an appendix in the dial section :
> > > > > >
> > > >
> > >
> >http://127.0.0.1:8080/cc/td/doc/product/software/ios121/121cgcr/dial_r/d
> >rdap
> > > > p
> > > > > > /index.htm
> > > > > >
> > > > > > Mostly related to chat scripts from what I see. BTW - I swear
> >that
> >if
> > > I
> > > > see a
> > > > > > chat script on the lab I'll get up and leave immediately.
> > > > > >
> > > > > > My confusion is not so much with the meaning of the expressions,
> >but
> > > > with how
> > > > > > they are interpreted by BGP. For instance, what's the
> >difference
> > > > between ^30$
> > > > > > and ^30_ ? Is it that ^30$ only matches 30 and nothing else and
> >^30_
> > > > matches
> > > > > > any path with 30 anywhere in it ?
> > > > > >
> > > > > > Does anyone have a standard set that they use that is somewhat
> >easy
> >to
> > > > > > remember ?
> > > > > >
> > > > > > TIA, Gregg
> > > > > >
This archive was generated by hypermail 2.1.4 : Thu Jun 13 2002 - 10:57:24 GMT-3