BGP EBGP Multihop


Scenario:

You are the junior network engineer for the biggest company in the world selling Arcade Games. You need to establish a BGP link with the service provider, in the future they will add another physical link for redundancy and so the provider wants you to setup the EBGP link between the loopback adapters for logical redundancy…time for some practice!

Goal:

  • All IP addresses have been preconfigured for you as specified in the topology picture.
  • Both routers have a loopback interface:
    Router Ping: L0: 1.1.1.1 /32
    Router Pong: L0: 2.2.2.2 /32
  • Configure static routes on both sides pointing to each others loopback.
  • Ensure you have full reachability and can ping both loopbacks.
  • Router Ping: configure BGP AS 100
  • Router Pong: configure BGP AS 200
  • Establish a BGP neighbor relationship between the 2 routers. You need to source the BGP updates from the loopback interfaces.
  • Ensure you have a BGP neighbor relationship, use the “show ip bgp summary” command to confirm this.

It took me 1000s of hours reading books and doing labs, making mistakes over and over again until I mastered all the routing protocols for CCNP.

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Does this sound interesting to you? Take a look here and let me show you how to Master CCNP ROUTE

IOS:

c3640-jk9s-mz.124-16.bin

Topology:

EBGP Multihop

Video Solution:

Configuration Files

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Once you are logged in you will find the configuration files right here.

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Written by René Molenaar - CCIE #41726

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About the Author: Rene Molenaar

René - CCIE #41726 is the creator of GNS3Vault.com where he shares CCNA, CCNP and CCIE R&S labs. He also blogs about networking on http://networklessons.com

15 Comments

  1. Hi very nice basic lab. Without spoaling the fun but i’m i correct when i say that bgp doesn’t see loopback as directly connected?

    Cheers,
    good site 😉

  2. Hi, My config is: router bgp 100
    no synchronization
    neighbor 192.168.12.2 remote-as 200
    neighbor 192.168.12.2 ebgp-multihop 3
    neighbor 192.168.12.2 update-source Loopback0

    with a similar one on the other router.
    After doing a clear ip bgp * the adj went down but never got up. Am I missing something here? All the other configs are done ok. The adj should have come up in my opinion.
    Thanks

  3. It worked, nice lab!

    **PING Router**
    router bgp 100
    no synchronization
    bgp log-neighbor-changes
    network 1.1.1.1 mask 255.255.255.255
    neighbor 2.2.2.2 remote-as 200
    neighbor 2.2.2.2 ebgp-multihop 3
    neighbor 2.2.2.2 update-source Loopback0
    no auto-summary

    Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
    2.2.2.2 4 200 8 9 4 0 0 00:02:27 0

  4. Very nice that’s the trick…now I have another challenge if you like 😉

    Try to solve this one without the “ebgp multihop” command and make sure updates are sourced from the loopback interfaces.

    I got the startup and final configs on my pc here, will upload them this weekend.

  5. hello rene can this be donw without using the comand update-source loopback what i think this can be done without this command to reach the network 2.2.2.2

  6. Nice basic lab.
    I understand that lab’s name "BGP EBGP MULTIHOP" means use command neighbor x.x.x.x ebgp-multihop. But if you want to make BGP neignbors from 2 adjacent router using their loopbacks you can just use neighbor x.x.x.x disable-connected-check.
    No need to use neither ebgp-multihop nor ttl-security.
    There is a good post about it http://lostintransit.se/tag/disable-connected-check/

  7. Could you maybe handle a scenario where you have:
    * 3 routers via frame-relay
    * R1 connects to R2
    * R1 connects to R3

    All interfaces in a single IP range: 172.16.4.0/24

    Then handle the different methods to manage the hop/ttl.

    on R2 “neighbor 172.16.4.x ebgp-multihop 2”
    &
    on R3 “neighbor 172.16.4.x ttl-security hop 2”

    I’m able to get the two routers to establish a BGP relationship when using either TTL-Security, or EBGP-MULTIHOP on both routers, but not when I mix them as with the scenario above.

    Please let me know if this sounds like a good lab, and I’ll email you the complete layout I have tested.

    1. The two are different. eBGP-multihop simply sets the TTL of the eBGP packet and, if the value is greater than 1, allows the router to use protocol-learned routes for BGP peers, versus just connected.

      TTL-security sets the TTL to 255. The value you specify is the difference from 255. A value greater than 1 allows the router to use protocol-learned routes for BGP peers, versus just connected.

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