Configuring GTSM for BGP
The Generalized TTL Security Mechanism (GTSM) protects a BGP session by comparing the TTL value in the IP header of incoming BGP packets against a valid TTL range. If the TTL value is within the valid TTL range, the packet is accepted. If not, the packet is discarded.
The valid TTL range is from 255 – the configured hop count + 1 to 255.
When GTSM is configured, the BGP packets sent by the device have a TTL of 255.
GTSM provides best protection for directly connected EBGP sessions, but not for multihop EBGP or IBGP sessions because the TTL of packets might be modified by intermediate devices.
![]() | IMPORTANT:
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To configure GTSM for BGP (IPv4 unicast/multicast address family):
Step | Command | Remarks |
---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter BGP instance view or BGP-VPN instance view. |
| N/A |
3. Configure GTSM for the specified BGP peer or peer group. | peer { group-name | ipv4-address [ mask-length ] } ttl-security hops hop-count | By default, GTSM is disabled. |
To configure GTSM for BGP (IPv6 unicast/multicast address family):
Step | Command | Remarks |
---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter BGP instance view or BGP-VPN instance view. |
| N/A |
3. Configure GTSM for the specified BGP peer or peer group. | peer { group-name | ipv6-address [ prefix-length ] } ttl-security hops hop-count | By default, GTSM is disabled. |