Home > BGP Sim

BGP Sim

February 4th, 2017 in Simlets Go to comments

Question

Loopback0 is used for IBGP peering while physical interface address is used for EBGP. Identify the IBGP issues on R1 to R2, R3 and EBGP issues to RA and fix them so that the “show ip bgp” command on R1 will display all loopback interfaces of other routers.

BGP_Topology.jpg

Special thanks to Yahya who created this BGP simlet with EVE-NG emulator and you can download it here.

Configs on R1:

This lab is for BGP only so we only need to check BGP section

R1#show running-config
—-output omitted—-
router bgp 64520
network 172.16.1.1 mask 255.255.255.255
neighbor IBGP peer-group
neighbor IBGP remote-as 64550
neighbor IBGP update-source loopback0
neighbor 172.16.2.2 peer-group IBGP
neighbor 172.16.3.3 peer-group IBGP
neighbor 209.165.200.2 remote-as 64525

—-output omitted—-

Solution

We see there are two issues here (two commands in bold), the first one is IBGP issue and the second one is EBGP issue.

R1(config)#router bgp 64520
R1(config-router)#neighbor IBGP remote-as 64520
R1(config-router)#no neighbor 209.165.200.2 remote-as 64525
R1(config-router)#neighbor 209.165.201.2 remote-as 64525

Note:
+ In the second statement we fix the IBGP group to “remote-as 64520” without removing the wrongly configured IBGP group (“neighbor IBGP remote-as 64550”) because if we remove this statement, other related statements of IBGP (three statements “neighbor IBGP update-source Loopback0”, “neighbor 172.16.2.2 peer-group IBGP”, “neighbor 172.16.3.3 peer-group IBGP”) will be removed automatically because IBGP group no longer exists.
+ Also in statement 2 the “IBGP” group must be written in capital. You will receive an error if writing it in lowercase.
+ The IP addresses in the exam are different but the concept is still the same so please read the question carefully

After solving the problem don’t forget to verify with the “show ip bgp” command. You must see all the Loopback interfaces of other routers. Otherwise please check your commands again.

Comments (11) Comments
Comment pages
1 4 5 6 993
  1. Fail exam
    May 21st, 2019

    I just failed exam.

    In BGP sim I do not have options to save config. Does anyone can tell me how to save my work?

    wr
    copy running-config startup-config – not working

  2. caj
    June 1st, 2019

    I have the next week, pls, can any one with the current dump share with me at: {email not allowed}

  3. Riaz
    June 13th, 2019

    i have exam on 24 june . if any have valid dumps please share. libra.ali1973 @ gmail . com

  4. Robert
    June 20th, 2019

    no need to save your config

  5. marimar
    June 20th, 2019

    EVE-NG file for this sim doesnt contain any config. anybody facing same?

  6. Lexxa
    June 26th, 2019

    Hello, After solving the problems whit the new comands the configuration in the R1 does not change so if type sh ip bgp i can not see all the Loopback interfaces of other routers.
    Do i have to save the configuration

  7. CONSULA
    July 3rd, 2019

    Hello Networktut, the sim provided is not working. After entering the commands, the running config doesn’t change. Is this a bug?

  8. CONSULA
    July 3rd, 2019

    Hello @Networktut, the sim provided is not working. After entering the commands, the running config doesn’t change. Is this a bug?

  9. networktut
    July 4th, 2019

    @CONSULA: It is not a bug. Our simulator can only show the initial config.

  10. Rosso
    July 5th, 2019

    I have no initial config. Does anybody have it?

  11. tshoots
    July 10th, 2019

    Use your own subnets to create a full topology and make sure you redistribute between protocols. For BGP you only advertise the loopbacks and then this will show up in the ‘show ip bgp’. This will also include the subnets of all the other networks. If you can ping the loop back of R3 from the loopback of RA, then your config should be sweet.

Comment pages
1 4 5 6 993