CISC-RT-000470 - The Cisco BGP switch must be configured to enable the Generalized TTL Security Mechanism (GTSM).

Information

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.

Solution

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

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_Cisco_IOS-XE_Switch_Y24M07_STIG.zip

Item Details

Category: SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|SC-5, CAT|III, CCI|CCI-002385, Rule-ID|SV-221021r856414_rule, STIG-ID|CISC-RT-000470, STIG-Legacy|SV-110863, STIG-Legacy|V-101759, Vuln-ID|V-221021

Plugin: Cisco

Control ID: ea600ecee024292cae189db91d264d5d87199a90fb20609507d2583de28a8503