Re: BGP AS-PATH PREPEND

As I undestand you want manipulate as-path atribute beetween two endpoint hosts
host 10.100.60.11 host 10.20.80.11.

In bgp we can do this manipulate [conrtol plane=updates bgp] in which
those host are.

We can set as-path preepend e.g to subnet in which is 10.100.60.11 or
10.20.80.11 on correct routers and correct directions.

those what you want it is posiible as marc wrote by pbr

correct mw if I'm wrong

On 1/8/14, marc abel <marcabel_at_gmail.com> wrote:
> Step 2 is where you are going to have trouble. You can advertise a host
> route to the MPLS cloud for your data replication (if your provider would
> accept /32 routes) and they would have to advertise a host route for your
> destination to you. But then all traffic to this destination is going to
> take the L2 path, not just traffic from your replication host, maybe that
> is the only traffic destined to the remote host so you don't care. Trying
> to specify source and destination will require policy based routing.
>
>
> On Wed, Jan 8, 2014 at 12:11 PM, Cisco Fanatic
> <ebay_products_at_hotmail.com>wrote:
>
>> 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
>> > >
>> > > > >
>> > >
>> > > > > __________________________________________________________________
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>> > >
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>> >
>> > --
>> > Marc Abel
>> > CCIE #35470
>> > (Routing and Switching)
>> >
>> >
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>
> --
> Marc Abel
> CCIE #35470
> (Routing and Switching)
>
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-- 
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