Title

The Cisco ACI must be configured to use its loopback address as the source address for internal Border Gateway Protocol (iBGP) peering sessions. (Cat III impact)

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 external BGP (eBGP) peering, the BGP session will be harder to hijack since the source address to be used is not known globally, making 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 the switch configuration to verify a loopback address has been configured. tenant <tenant-name> networking l3out <l3out-name> protocol BGP neighbor 10.1.1.1 update-source Loopback0 If the switch does not use its loopback address as the source address for all iBGP sessions, this is a finding.

Fix Text

Configure the BGP configuration for the relevant L3Out to use the switch's loopback address as the source address for all iBGP peering. This configures the switch to use the loopback interface as the source IP for all BGP updates sent to the specified peer. tenant <tenant-name> networking l3out <l3out-name> protocol BGP neighbor <peer-ip> update-source Loopback0

Additional Identifiers

Rule ID: SV-272098r1064501_rule

Vulnerability ID: V-272098

Group Title: SRG-NET-000512-RTR-000001

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.