Tag Archives: BGP

eBGP Loopbacks: Multihop vs Disable Connected Check

By default, BGP checks if its configured external (or eBGP) peers are directly connected. If not, BGP will not initialize for those peers (will stuck in Init). Respectively, this is true when destination’s IP address belongs to a loopback interface, even though it is configured on the directly connected router. Moreover, default TTL value for eBGP packets is 1 (that is why the check is required). There are two ways to change router’s default behavior – configure eBGP multihop or disable the check for directly connected peers. They both do same thing for loopback interfaces, yet the logic is different. Continue reading