V-273654

Discussion

Using a loopback address as the source address offers a multitude of uses for security, access, management, and scalability of the BGP routers. It is easier to construct appropriate ingress filters for router management plane traffic destined to the network management subnet since the source addresses will be from the range used for loopback interfaces instead of a larger range of addresses used for physical interfaces. Log information recorded by authentication and syslog servers will record the router's loopback address instead of the numerous physical interface addresses. When the loopback address is used as the source for eBGP peering, the BGP session will be harder to hijack because the source address to be used is not known globally. This makes it more difficult for a hacker to spoof an eBGP neighbor. By using traceroute, a hacker can easily determine the addresses for an eBGP speaker when the IP address of an external interface is used as the source address. The routers within the iBGP domain should also use loopback addresses as the source address when establishing BGP sessions.

Check Content

Review configuration to verify BGP configuration uses the loopback address as the source address for iBGP peering sessions.  

interface loopback 1
 ip address x.x.1.1 255.255.255.255
!
router bgp
 local-as 10
 neighbor x.x.x.x remote-as 10
 neighbor x.x.x.x update-source loopback 1

If the router is not using a loopback address as the source for iBGP peering sessions, this is a finding.