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I have above scenario where i have multiple PATH for my BGP so i have to setup loopback interface to make it ECMP routing on both path.

I have cisco nexus switches and following is my first router config:

router bgp 65001
  log-neighbor-changes
  address-family ipv4 unicast
    network 200.200.200.0/24
  neighbor 10.0.0.1
    remote-as 65002

Question:

  • do i need to add update-source loopback0 in bgp config and why?
  • do i need ebgp-multihop 2 ( I doubt because it use for two different path to different devices)

let me know anything i missing here?

EDIT:

loopback doesn't support access-list in that case do i need to add access list on my two physical interface?

Router running eBGP ( sorry i forgot to mention )

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3
  • Your diagram is confusing because it only lists a single AS, so that would be iBGP. It is eBGP if it is between two different ASes.
    – Ron Maupin ♦
    Jun 5, 2019 at 19:50
  • 1
    Your configuration shows iBGP. Please edit the listing and/or diagram to reflect that.
    – Ron Trunk
    Jun 5, 2019 at 19:50
  • It was typo, anyway I have fixed AS number now it’s different AS. Sorry for that.
    – Satish
    Jun 9, 2019 at 0:38

2 Answers 2

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5

Do I need to add update-source loopback0 in BGPconfig and why?

Yes, otherwise the router will use the closest interface, which would be either f0/0 or f0/1. The BGP process is expecting the BGP packet's source address to be the one listed in the neighbor statement, so the peering will never form. You also need to have IGP routing so that your loopbacks are reachable from each other.

Do I need ebgp-multihop 2?

No. Since you are using iBGP, not eBGP, there is no need for the ebgp-multihop statement.

Note: You might consider configuring the two links as a single Etherchannel, which may make things easier to understand/troubleshoot.

EDIT

If you're trying to secure your BGP peers, an easier way might be to configure BGP keys on the peer. They act like passwords, authenticating the BGP session.

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14
  • 2
    I think the layer-3 etherchannel is a very good idea. It can simplify things, and it will fail over the fastest.
    – Ron Maupin ♦
    Jun 5, 2019 at 17:51
  • Thanks, i have edit my question - loopback doesn't support access-list in that case do i need to add access list on my two physical interface?
    – Satish
    Jun 5, 2019 at 17:59
  • instead of IGP i can use static route also right?
    – Satish
    Jun 5, 2019 at 18:02
  • 1
    Yes, put them on the physical interfaces. Also, you can apply ACLs on the VTY and SNMP.
    – Ron Trunk
    Jun 5, 2019 at 18:41
  • 2
    Then you're running eBGP. Please edit your question to reflect that.
    – Ron Trunk
    Jun 5, 2019 at 19:07
-1

maximum-paths eibgp x

replace the number with X ( your total paths )

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    Welcome to NE, we hope you will both contribute to and learn from this community. You could improve your answer by editing it to add more details to make it more useful both for the original poster and future users. Typically short answers like this could provide reasoning why you believe this is the answer, more explanation about the concepts mentioned, references/links to supporting resources, or applicable examples.
    – YLearn
    Jun 7, 2019 at 20:57

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