Re: BGP AS-PATH PREPEND

You can do that with QOS but not directly through BGP.

On Fri, Jan 10, 2014 at 1:40 PM, Cisco Fanatic
<ebay_products_at_hotmail.com>wrote:

> 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 65500
>
> neighbor 10.255.255.1 route-map WEIGHT_CHANGE in
>
> !
>
> route-map WEIGHT_CHANGE permit 10
>
> set weight 100
>
>
>
> R2:
>
> router bgp 65501
>
> neighbor 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 Systems
>
> www.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<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
> > >
> > > > >
> > >
> > > > > __________________________________________________________________
> > > > > _____
> > >
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> > >
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> > >
> > > > ____________________________________________________________________
> > > > ___
> > >
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> > >
> >
> >
> > --
> > Marc Abel
> > CCIE #35470
> > (Routing and Switching)
> >
> >
> > Blogs and organic groups at http://www.ccie.net
> >
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>

--
Marc Abel
CCIE #35470
(Routing and Switching)
Blogs and organic groups at http://www.ccie.net