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

Information

As described in RFC 3682, GTSM is designed to protect a router's IP-based control plane from denial of service (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.

Solution

Configure TTL security on all external BGP neighbors as shown in the example below:

R1(config)#router bgp xx
R1(config-router)#neighbor x.1.1.9 ttl-security hops 1
R1(config-router)#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_Router_Y24M07_STIG.zip

Item Details

Category: SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|SC-5, CAT|III, CCI|CCI-002385, Rule-ID|SV-216999r855842_rule, STIG-ID|CISC-RT-000470, STIG-Legacy|SV-106081, STIG-Legacy|V-96943, Vuln-ID|V-216999

Plugin: Cisco

Control ID: bfd0262c81be3082c719aa9ff2e915ef3c2739ec41f8dafb656d6898b3fa4ba1