The router is unable to establish a connection with a Border Gateway Protocol (BGP) neighbor that is not its next hop. This article explains what to do to resolve the problem.

We use a time to live (TTL) value of 1 in the EBGP session packets to ensure that the EBGP session cannot be established across any other backdoor links in the network. If the peer is more than one hop away, the BGP session will not establish. Therefore the knob "multihop" must be used.

Multihop needs to be set up to allow BGP to know that its neighbor is not the next hop, but further upstream. This option is added at the BGP group level.

Example

[edit protocols bgp]
user@router#  show 
local-as 200;
group ebgp1 {
    type external;
     multihop {
        ttl 3;
        no-nexthop-change; 
    }
    export static-to-bgp;
    peer-as 100;
    neighbor 10.0.0.2 {
        local-address 10.0.0.1;
    }
} 

For additional details, see BGP Multihop Sessions.

2020-07-17​ : Article reviewed for accuracy; minor non-technical edits

2022-08-16: Added BGP multihop sessions documentation link