The Cisco BGP switch must be configured to enable the Generalized TTL Security Mechanism (GTSM).
An XCCDF Rule
Description
As described in RFC 3682, GTSM is designed to protect a switch'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 switches. GTSM is based on the fact that the vast majority of control plane peering is established between adjacent switches; 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.
- ID
- SV-221021r856414_rule
- Version
- CISC-RT-000470
- Severity
- Low
- References
- Updated
Remediation Templates
A Manual Procedure
Configure TTL security on all external BGP neighbors as shown in the example below:
SW1(config)#router bgp xx
SW1(config-switch)#neighbor x.1.1.9 ttl-security hops 1
SW1(config-switch)#neighbor x.2.1.7 ttl-security hops 1