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Latest post 10-30-2008 9:49 AM by ciscokid. 5 replies.
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  • 10-29-2008 8:13 PM

    BGP update

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    how to configure the bgp neighbor with the route-map so that local AS will elect that router as a exit to the other AS if i have multihome secnario?

    what are the attributes with route-map with in and out keywork I can advertise to local AS iBGP peer and to eBGP peer to select local router as a exit point to the prefixes of the remote AS.

    regards

    Divya

     
    • Post Points: 35

  • 10-30-2008 12:53 AM In reply to

    • nomykhan
    • Top 75 Contributor
    • Joined on 07-17-2008
    • Posts 19
    • Points 365

    Re: BGP update

    Reply Contact

    To prefer a router in your local AS with multi-homed AS , the best option i can think of is local-preference.

    route-map LOCAL per 10

    match ip address 10

    set local-pre 150

     

    router bgp 10

    neighbor 1.1.1.1 route-map LOCAL in

     

    If the remote needs to do that , than MED will shld be the right option

     

    HTH
    • Post Points: 20

  • 10-30-2008 1:54 AM In reply to

    • msemsem79
    • Top 200 Contributor
    • Joined on 09-28-2008
    • Posts 8
    • Points 85

    Re: BGP update

    Reply Contact
    Local-Preference is good for IBGP but I prefer AS-Path prepending in real life as MED is considered as a weak attribute.

    From: nomykhan <bounce-nomykhan@ieoc.com>
    To: msemsem79@yahoo.com
    Sent: Thursday, October 30, 2008 9:53:43 AM
    Subject: Re: [CCIE SP] BGP update

    To prefer a router in your local AS with multi-homed AS , the best option i can think of is local-preference.

    route-map LOCAL per 10

    match ip address 10

    set local-pre 150

     

    router bgp 10

    neighbor 1.1.1.1 route-map LOCAL in

     

    If the remote needs to do that , than MED will shld be the right option

     

    HTH




    Internetwork Expert - The Industry Leader in CCIE Preparation
    http://www.internetworkexpert.com

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    http://www.ieoc.com/forums/ForumSubscriptions.aspx
    • Post Points: 20

  • 10-30-2008 6:26 AM In reply to

    Re: BGP update

    Reply Contact

    Thanks for your responses, how can i work out if i have been told to configure my local router with the "neighbor route-map out", so that my local AS networks will elect one router as the primary and other as a secondary to send traffic out to the other AS.

    lets say i have 7 router topology, like R1 R2 R3 R4 R5 are in one AS(AS1) and R6 and R7 are in other AS(AS2), where R1 and R2 is the edge router, R1 is connected with R6 and R2 is connected with R7 in other AS, now i have only option to configure R1 and R6 with the route-map out to achieve the R1 as a primary router to send traffic to AS2, i dont have option to configure R2 and R7!

    how can i achieve this?

     

     
    • Post Points: 20

  • 10-30-2008 8:48 AM In reply to

    • msemsem79
    • Top 200 Contributor
    • Joined on 09-28-2008
    • Posts 8
    • Points 85

    Re: BGP update

    Reply Contact
    If you want to make R1 as a primary BGP gateway for AS1 so Local Preference is enough to be set in output route-map to R1' IBGP peers. If you want to make R1 to be the primary entry point for AS2 you can do the same on R6 using output route-map to R6' IBGP peers.
    BGP controls outgoing traffic with 100% capability.

    From: div_er2001 <bounce-div_er2001@ieoc.com>
    To: msemsem79@yahoo.com
    Sent: Thursday, October 30, 2008 3:28:47 PM
    Subject: Re: [CCIE SP] BGP update

    Thanks for your responses, how can i work out if i have been told to configure my local router with the "neighbor route-map out", so that my local AS networks will elect one router as the primary and other as a secondary to send traffic out to the other AS.

    lets say i have 7 router topology, like R1 R2 R3 R4 R5 are in one AS(AS1) and R6 and R7 are in other AS(AS2), where R1 and R2 is the edge router, R1 is connected with R6 and R2 is connected with R7 in other AS, now i have only option to configure R1 and R6 with the route-map out to achieve the R1 as a primary router to send traffic to AS2, i dont have option to configure R2 and R7!

    how can i achieve this?

     

     




    Internetwork Expert - The Industry Leader in CCIE Preparation
    http://www.internetworkexpert.com

    Subscription information may be found at:
    http://www.ieoc.com/forums/ForumSubscriptions.aspx
    • Post Points: 5

  • 10-30-2008 9:49 AM In reply to

    • ciscokid
    • Top 75 Contributor
    • Joined on 09-11-2008
    • South Africa
    • Posts 20
    • Points 310

    Re: BGP update

    Reply Contact
    Re: [CCIE SP] BGP update Here goes:

    To effect in-comming routes to you from another AS. Choose the specific routes required and set the “local-pref” attribute inbound.

    E.g. Set local-pref 1000 (highest value wins- BGP default is 100)

    For you to effect the routing choice of another AS then you need to either set the med “metric” or prepend your own AS to your required networks outbound. Your network will then “seem” further away as your neighbor will have a route with a higher hop count. BGP prefers the routes with the least AS path hops.

    Set as-path prepend 2 2 2 2 (AS 2 is added 4 times ) so when the neighbor receives the routes form your boundry routers then one route will be 1 hop and the other 5 hops. So the route with 1 hop will be advertised within their AS for next hop reachability.

    Or

    Set metric 1000 (with med the lower value is preferred)

    Hope that helps and have fun manipulating your routes.

    James


    On 10/30/08 5:16 AM, "div_er2001" <bounce-div_er2001@ieoc.com> wrote:

    how to configure the bgp neighbor with the route-map so that local AS will elect that router as a exit to the other AS if i have multihome secnario?

    what are the attributes with route-map with in and out keywork I can advertise to local AS iBGP peer and to eBGP peer to select local router as a exit point to the prefixes of the remote AS.

    regards

    Divya

     




    Internetwork Expert - The Industry Leader in CCIE Preparation
    http://www.internetworkexpert.com

    Subscription information may be found at:
    http://www.ieoc.com/forums/ForumSubscriptions.aspx
    • Post Points: 5
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