H3C Technologies H3C S5560 Series Switches - Manual (Page 265)

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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.
To configure GTSM for BGP (IPv4 unicast/multicast address family):
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter BGP view or BGP-VPN
instance view.
• Enter BGP view:
bgp as-number
• Enter BGP-VPN instance view:
a. bgp as-number
b. ip vpn-instance vpn-instance-name
N/A
3. Configure GTSM for the
specified BGP peer or peer
group.
peer { group-name | ip-address
[ mask-length ] } ttl-security hops hop-count By default, GTSM is not
configured.
To configure GTSM for BGP (IPv6 unicast/multicast address family):
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter BGP view or BGP-VPN
instance view.
• Enter BGP view:
bgp as-number
• Enter BGP-VPN instance view:
a. bgp as-number
b. ip vpn-instance vpn-instance-name
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 not
configured.
Configuring BGP soft-reset
After you modify the route selection policy, for example, modify the preferred value, you must reset BGP
sessions to apply the new policy. The reset operation tears down and re-establishes BGP sessions.
To avoid tearing down BGP sessions, you can use one of the following soft-reset methods to apply the
new policy:
• Enabling route-refresh—The BGP router advertises a route-refresh message to the specified peer,
and the peer resends its routing information to the router. After receiving the routing information, the
router filters the routing information by using the new policy.
This method requires that both the local router and the peer support route refresh.
• Saving updates—Use the peer keep-all-routes command to save all route updates from the
specified peer. After modifying the route selection policy, filter routing information by using the new
policy.
This method does not require that the local router and the peer support route refresh but it uses
more memory resources to save routes.