Title

The Arista BGP router must be configured to enable the Generalized TTL Security Mechanism (GTSM). (Cat III impact)

Discussion

GTSM is designed to protect a router's IP-based control plane from DoS attacks. Many attacks focused on CPU load and line-card overload can be prevented by implementing GTSM on all Exterior Border Gateway Protocol speaking routers. GTSM is based on the fact that the vast majority of control plane peering is established between adjacent routers; that is, the Exterior Border Gateway Protocol peers are either between connecting interfaces or between loopback interfaces. Since TTL spoofing is considered nearly impossible, a mechanism based on an expected TTL value provides a simple and reasonably robust defense from infrastructure attacks based on forged control plane traffic.

Check Content

Review the Arista router configuration. Arista MLS IP packets to GTSM enabled BGP peers are sent with the configured TTL value of 254. router bgp NNN neighbor 10.1.12.2 ttl maximum-hops 2 If the Arista router is not configured to use GTSM for all Exterior Border Gateway Protocol peering sessions, this is a finding.

Fix Text

Configure all Exterior Border Gateway Protocol peering sessions to use GTSM. router bgp 65000 neighbor 10.1.12.2 ttl maximum-hops 2

Additional Identifiers

Rule ID: SV-256039r882459_rule

Vulnerability ID: V-256039

Group Title: SRG-NET-000362-RTR-000124

Expert Comments

CCIs tied to check.

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