EBGP – External BGP


Scenario:

Textilalicious is a large international company specialized in selling Wool, Silk, Cotton and Flax. Each region is specialized in selling a different type of textile. To support the growth of the company network your boss has decided to use BGP to connect the different regions together. You just finished studying BGP for your CCNP ROUTE exam so your boss agrees to let you configure this network.

Goal:

  • All IP addresses have been preconfigured for you as specified in the topology picture.
  • Configure EBGP between AS 1 and AS 2.
  • Configure EBGP between AS 2 and AS 3. You are not allowed to use the IP addresses on the physical interfaces to configure the BGP neighbor adjacency.
  • Configure EBGP between AS 3 and AS 4.
  • Advertise the loopback interfaces in BGP and ensure you have full reachability for this network.

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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You will learn all the secrets about BGP, the difference between IBGP and EBGP and more.

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

IOS:

c3640-jk9o3s-mz.124-16.bin

Topology:

External BGP

Video Solution:

Configuration Files

You need to register to download the GNS3 topology file. (Registration is free!)

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

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The How to Master series helps you to understand complex topics like spanning-tree, VLANs, trunks, OSPF, EIGRP, BGP and more.

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

20 Comments

  1. Thanks Uffe! It’s a simple network but it’ll teach you everything you need to know about EBGP.

  2. Another great lab (Good job on sneaking in small problems, despite a few apparently simple goals – I wont post any spoilers 😉 )

  3. Thanks, I’ll keep working until everything is at CCIE R&S level. I’ve been working on building new BGP labs and it will take some time to catch up with everything.

  4. Hi Rene,

    I am unsure why the ebgp-mulithop was used in this exercise. What is the purpose of this command option? The iBGP lab used loopbacks as their neighbors but did not require using ebgp-mulithop. Can you please explain this for my understanding?

    Thank you,
    Bong

    1. Hello Bong,

      By default EBGP routers will send IP packets with a TTL of 1. This means you can only configure EBGP neighbor adjacencies using the IP addresses on the directly connected interfaces.

      If you want to configure EBGP between loopback interfaces you’ll need to use the EBGP multihop command.

      IBGP does not have this "restriction" so we don’t have to use a multihop command for this.

      Rene

    1. @ E_mad

      That part threw me for a loop also, I had the entire lab configured correctly and finally had to view the final config to see static routes were missing………. I will have to review the chapter and look for the info about using those staticroutes

  5. Thank rane.. for such mathod of thech…. in books and lab… hope it has helped many people and will keep going on… thanks again

  6. uhm rene, if we want to advertise directly connected network between two ebgp routers, should we advertise that network in both routers or not ?
    Thank you

  7. i did not have the exact IOS code version listed for this lab; therefore, i tried what i had.
    none of my c3640, c3725, or c3745 IOS code versions worked… kept getting “inaccessible” 2.2.2.2 and 3.3.3.3 between Flax and Silk respectively (even when i loaded the final configs from Rene).

    switched over to c7200 and everything worked fine LOL.
    just thot i’d share 🙂

    GNS3 version 0.8.3

    IOS versions that did NOT work for me:
    c3640-ik9o3s-mz.124-16b.bin
    c3640-ik9o3s-mz.124-25d.bin
    c3725-adventerprisek9-mz.124-15.T10.bin
    c3745-adventerprisek9-mz.124-15.T10.bin

    IOS version that DID work for me:
    c7200-adventerprisek9-mz.124-24.T8.bin

  8. Hi Rene Molenaar,
    Please help me to clarify this point:
    At 6:21, after we “network 192.168.12.0 mask 255.255.255.0” on Wool router, we can ping 3.3.3.3 OK.

    Wool#ping 3.3.3.3

    Type escape sequence to abort.
    Sending 5, 100-byte ICMP Echos to 3.3.3.3, timeout is 2 seconds:
    !!!!!
    Success rate is 100 percent (5/5), round-trip min/avg/max = 28/51/68 ms

    But before that, we can not ping 3.3.3.3 because Router Flax do not have knowlegde about network 192.168.12.0? That right?

    But when I use traceroute 3.3.3.3, the route stop at below:

    Wool#traceroute 3.3.3.3

    Type escape sequence to abort.
    Tracing the route to 3.3.3.3

    1 192.168.12.2 24 msec 64 msec 24 msec
    2 * * *
    3 * * *
    4 * * *
    5 * * *
    6 * * *
    7 * * *
    8 * * *
    9 * * *
    10 * * *
    11 * * *
    12 * * *
    13 * * *
    14 * * *
    15 * * *
    16 * * *
    17 * * *
    18 * * *
    19 * * *
    20 * * *
    21 * * *
    22 * * *
    23 * * *
    24 * * *
    25 * * *
    26 * * *
    27 * * *
    28 * * *
    29 * * *

    This mean route stop at router Silk?

  9. Unfortunately it’s is impossible to start this new lab format. I tried arond 5-6 different images, it always either sticks at boot or is unresponsive. Please help. My CCNP route exam is in a week:))). Is there a way to download the old versions?

  10. please help me to understand further. why the network 192.168.23.0/24 not being advertised by router Flax as well under bgp network command? why any network advertisement between two routers, is done by only one router for bgp? is this to prevent bgp loop mechanism?..appreciate your soonest reply on this as i will be sitting for ccnp exam.

Comments are closed.