Finding ID | Version | Rule ID | IA Controls | Severity |
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V-216999 | CISC-RT-000470 | SV-216999r531086_rule | Low |
Description |
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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. |
STIG | Date |
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Cisco IOS XE Router RTR Security Technical Implementation Guide | 2021-09-16 |
Check Text ( C-18229r288159_chk ) |
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Review the BGP configuration to verify that TTL security has been configured for each external neighbor as shown in the example below: router bgp xx no synchronization bgp log-neighbor-changes neighbor x.1.1.9 remote-as yy neighbor x.1.1.9 password xxxxxxxx neighbor x.1.1.9 ttl-security hops 1 neighbor x.2.1.7 remote-as zz neighbor x.2.1.7 password xxxxxxxx neighbor x.2.1.7 ttl-security hops 1 If the router is not configured to use GTSM for all Exterior Border Gateway Protocol peering sessions, this is a finding. |
Fix Text (F-18227r288160_fix) |
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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 |