Ok. I will try this.
What if one of my link goes down. For example - MPLS link between R1 and R3
goes down. My understanding is that all the traffic will re-route to Layer 2.
Is there a way to make sure that we can set priority so that traffic
originating from 10.80.10.0/24 takes priority over 10.80.20.0/24 (say).
From: jeff_at_tydesystems.com
To: ebay_products_at_hotmail.com; marcabel_at_gmail.com
CC: sammybibs_at_gmail.com; mothafungla_at_gmail.com; ccielab_at_groupstudy.com
Subject: RE: BGP AS-PATH PREPEND
Date: Wed, 8 Jan 2014 11:46:11 -0700
Now I see where your confusion is. You cant do AS path prepend for a path
like it looks like youre thinking. AS path prepend is used for manipulating
routes (as Marc mentioned) generally to a provider to affect the cloud
whether it be MPLS or internet. Also since you need to affect traffic in both
directions generally you would need to use something like Weight or Local
Preference as well as AS path prepend to manipulate traffic coming out of R1
and R2 as well as traffic coming back from R3. In your specific scenario you
can set Weight on both R1 and R2 (granted they are in different BGP ASs) for
all traffic from R3 and not worry about AS path prepend. This way all the
routes from R3 will have a higher weight (on both R1 and R2) and therefore be
preferred over routes from R1 and R2. Also good work with all caps on your
route-map statements! This is what I recommend as it helps with typos using a
combination of upper and lower case. Please note Im making some assumptions
here with the BGP ASs you are using. Please let me know if you have any
questions. -------------------- R1:router bgp 65500neighbor 10.255.255.1
route-map WEIGHT_CHANGE in ! route-map WEIGHT_CHANGE permit 10 set weight 100
R2:router bgp 65501neighbor 10.255.255.21 route-map WEIGHT_CHANGE in !
route-map WEIGHT_CHANGE permit 10 set weight 100 --------------------- Jeffrey
Lodwick - CCIE 15671 R&S
Senior Data Engineer / Owner
Jeff_at_tydesystems.com
Office: 303-346-9988
Mobile: 303-919-1366
Tyde Systemswww.tydesystems.com From: Cisco Fanatic
[mailto:ebay_products_at_hotmail.com]
Sent: Wednesday, January 08, 2014 11:12 AM
To: Jeff Lodwick; 'marc abel'
Cc: 'Sam Bibby'; 'Tony Singh'; ccielab_at_groupstudy.com
Subject: RE: BGP AS-PATH PREPEND Let me try to put this is perspective so that
I help myself understand BGP effectively. This is how I have setup in my lab.
Topology
++++++++
R1 (10.255.0.25) ------------------ (10.255.0.26) R2
|
|
(10.3.0.1) (10.13.0.1)
| |
| |
(10.255.255.1) (10.255.255.21)
R3
R1 & R2 is directly connected. Think of it as P-2-P link, I call it Layer 2
connection.
R3 is a router in simulated MPLS cloud.
R1 second interface 10.3.0.1 is connected to R3 10.255.255.1
R2 second interface 10.13.0.1 is connected to R3 10.255.255.21
Objective
++++++++
1) All traffic originated by users and systems in R2 that is accessing R1 will
utilize the MPLS cloud as the primary path with the Layer 2 as their secondary
path.
2) Data replication traffic will only utilize Layer 2 as the primary path.
3) In the event connectivity between R1 & R3 is lost, all traffic should
traverse Layer 2.
-Yuri
> From: jeff_at_tydesystems.com
> To: marcabel_at_gmail.com; ebay_products_at_hotmail.com
> CC: sammybibs_at_gmail.com; mothafungla_at_gmail.com; ccielab_at_groupstudy.com
> Subject: RE: BGP AS-PATH PREPEND
> Date: Wed, 8 Jan 2014 10:45:09 -0700
>
> Marc,
> You are correct here. That's why I was asking where this host route was
> because I didn't see it in the BGP table and I didn't see a network
> statement advertising it (if it's in the IGP table already).
>
> Jeffrey Lodwick - CCIE 15671 R&S
> Senior Data Engineer / Owner
> Jeff_at_tydesystems.com
> Office: 303-346-9988
> Mobile: 303-919-1366
>
> www.tydesystems.com
>
>
> -----Original Message-----
> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
marc
> abel
> Sent: Wednesday, January 08, 2014 10:20 AM
> To: Cisco Fanatic
> Cc: Sam Bibby; Tony Singh; ccielab_at_groupstudy.com
> Subject: Re: BGP AS-PATH PREPEND
>
> That access-list isn't going to match any routes. Remember you are matching
> routes not flows so you can't specify a source and destination.
>
>
> On Wed, Jan 8, 2014 at 10:53 AM, Cisco Fanatic
> <ebay_products_at_hotmail.com>wrote:
>
> > Because I only want 10.100.60.11 (source) to go over Layer 2 (a name)
> > 10.20.80.11 (destination). The rest should all be prepended.
> >
> > ip access-list extended OVER_L2
> > permit ip host 10.100.60.11 host 10.20.80.11
> >
> > With your suggestion all the traffic will be prepended (longer AS
> > path) and it will not be the best route.
> >
> >
> > Date: Wed, 8 Jan 2014 16:36:40 +0000
> > Subject: Re: BGP AS-PATH PREPEND
> > From: sammybibs_at_gmail.com
> > To: ebay_products_at_hotmail.com
> > CC: mothafungla_at_gmail.com; ccielab_at_groupstudy.com
> >
> > I'm pretty sure the route map is wrong here,
> >
> > !!!Yours
> >
> > !
> > !You match the ACL but don't do anything with it.
> > !
> >
> > route-map AS_CHANGE permit 10
> >
> > match ip address OVER_L2
> >
> > !
> > ! You then pre-pend everything via the match all in the next statement
> > !
> >
> > route-map AS_CHANGE permit 20
> >
> > set as-path prepend 65500 65500 65500
> >
> > !
> >
> >
> > !!!Suggestion
> >
> > !
> > !You match the ACL but don't do anything with it.
> > !
> >
> > route-map AS_CHANGE permit 10
> >
> > match ip address OVER_L2
> > set as-path prepend 65500 65500 65500 !
> >
> > \Sam
> >
> >
> > On Wed, Jan 8, 2014 at 4:31 PM, Cisco Fanatic
> > <ebay_products_at_hotmail.com>
> > wrote:
> >
> > Sorry, cut-paste issue, too many notepad open.
> >
> >
> > R1
> >
> > ++
> >
> >
> > !
> >
> > router bgp 65500
> >
> > neighbor 10.255.0.26 route-map AS_CHANGE out
> >
> > !
> >
> > route-map AS_CHANGE permit 10
> >
> > match ip address OVER_L2
> >
> > !
> >
> > route-map AS_CHANGE permit 20
> >
> > set as-path prepend 65500 65500 65500
> >
> > !
> >
> > ip access-list extended OVER_L2
> >
> > permit ip host 10.100.60.11 host 10.20.80.11
> >
> > !
> >
> >
> > It is still going over the other connection...
> >
> >
> > R1#traceroute 10.20.80.11
> >
> > Type escape sequence to abort.
> >
> > Tracing the route to 10.20.80.11
> >
> > VRF info: (vrf in name/id, vrf out name/id)
> >
> > 1 10.255.255.1 4 msec 0 msec 4 msec
> >
> > 2 10.255.255.22 [AS 1] 4 msec 0 msec 4 msec
> >
> > 3 10.13.0.253 [AS 65501] 4 msec 4 msec 0 msec
> >
> >
> >
> >
> >
> >
> >
> > > Subject: Re: BGP AS-PATH PREPEND
> >
> > > From: mothafungla_at_gmail.com
> >
> > > Date: Wed, 8 Jan 2014 15:59:21 +0000
> >
> > > CC: ccielab_at_groupstudy.com
> >
> > > To: ebay_products_at_hotmail.com
> >
> > >
> >
> > > Where's your match extended ACL in route-map condition ?
> >
> > >
> >
> > > --
> >
> > > BR
> >
> > >
> >
> > > Tony
> >
> > >
> >
> > > > On 8 Jan 2014, at 15:47, Cisco Fanatic <ebay_products_at_hotmail.com>
> > wrote:
> >
> > > >
> >
> > > > I understand how AS-PATH PREPEND works, but I am not able to make
> > > > it
> > work
> >
> > if I
> >
> > > > need to manipulate traffic paths only from a specific source to a
> >
> > specific
> >
> > > > destination.
> >
> > > >
> >
> > > > R1
> >
> > > > ++
> >
> > > >
> >
> > > > !
> >
> > > > router bgp 65500
> >
> > > >
> >
> > > > neighbor 10.255.0.26 route-map AS_CHANGE out
> >
> > > >
> >
> > > > !
> >
> > > > route-map AS_CHANGE permit 10
> >
> > > >
> >
> > > > set as-path prepend 65500 65500 65500
> >
> > > >
> >
> > > > !
> >
> > > >
> >
> > > > R2
> >
> > > > ++
> >
> > > >
> >
> > > > !
> >
> > > > router bgp 65501
> >
> > > >
> >
> > > > neighbor 10.255.0.25 route-map AS_CHANGE out
> >
> > > >
> >
> > > > !
> >
> > > > route-map AS_CHANGE permit 10
> >
> > > >
> >
> > > > set as-path prepend 65501 65501 65501
> >
> > > >
> >
> > > > !
> >
> > > >
> >
> > > > R1#sh ip bgp
> >
> > > > BGP table version is 196, local router ID is 10.255.255.2
> >
> > > > Status codes: s suppressed, d damped, h history, * valid, > best,
> > > > i -
> >
> > > > internal,
> >
> > > > r RIB-failure, S Stale, m multipath, b backup-path, x
> >
> > > > best-external, f RT-Filter
> >
> > > > Origin codes: i - IGP, e - EGP, ? - incomplete
> >
> > > > Network Next Hop Metric LocPrf Weight Path
> >
> > > > *> 10.3.0.0/16 0.0.0.0 0 32768 ?
> >
> > > > *> 10.7.0.0/24 0.0.0.0 0 32768 ?
> >
> > > > *> 10.11.0.0/24 0.0.0.0 0 32768 ?
> >
> > > > *> 10.13.0.0/16 10.255.255.1 0 1 65501 ?
> >
> > > > * 10.255.0.26 0 0 65501
> > 65501
> >
> > 65501
> >
> > > > 65501 ?
> >
> > > > *> 10.16.0.0/24 0.0.0.0 0 32768 ?
> >
> > > > *> 10.20.0.0/24 10.255.255.1 0 1 65501 ?
> >
> > > > * 10.255.0.26 28416 0 65501
> > 65501
> >
> > 65501
> >
> > > > 65501 ?
> >
> > > >
> >
> > > > I need specific traffic from 10.100.60.11 (Source) to specific
> >
> > 10.20.80.11
> >
> > > > (Destination) over the 10.255.0.26 connection.
> >
> > > >
> >
> > > >
> >
> > > > 10.100.60.11
> >
> > > > _` 10.20.80.11
> >
> > > >
> >
> > > >
> >
> > > > Any thoughts?
> >
> > > >
> >
> > > >
> >
> > > > 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
> >
> >
> > ______________________________________________________________________
> > _
> >
> > 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
> >
> >
> >
> >
> >
> >
> >
> >
>
>
> --
> Marc Abel
> CCIE #35470
> (Routing and Switching)
>
>
> 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 Fri Jan 10 2014 - 11:40:34 ART
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