BGP-Neighbor Disable-Connected-Check

One way of resolving non directly connected peer problem is to simply increase the TTL between the peers. In designs where the peers are directly connected but the peering address is a Loopback instead of the connected interface between them, the  disable-connected-check neighbor option may also be used. Although similar in result to increasing the EBGP TTL, the difference between these features is that the  disable-connected-check prevents cases in which the EBGP session between two devices is routed over another transit router.




R1(config-router)#do show run | s bgp
router bgp 65001
 no synchronization
 bgp log-neighbor-changes
 neighbor 3.3.3.3 remote-as 65003
 neighbor 3.3.3.3 ebgp-multihop 3
 neighbor 3.3.3.3 disable-connected-check
 neighbor 3.3.3.3 update-source Loopback0
 no auto-summary

R3(config-router)#do show run | s bgp
router bgp 65003
 no synchronization
 bgp log-neighbor-changes
 neighbor 1.1.1.1 remote-as 65001
 neighbor 1.1.1.1 ebgp-multihop 3
 neighbor 1.1.1.1 disable-connected-check
 neighbor 1.1.1.1 update-source Loopback0
 no auto-summary