67Step Command Remarks3. Specify the type of the label tobe distributed by the egress tothe penultimate hop.label advertise { explicit-null |implicit-null | non-null }Optional.By default, an egress distributes tothe penultimate hop an implicit nulllabel.Configuring the policy for triggering LSP establishmentYou can configure an LSP triggering policy on an LSR, so only routes matching the policy can triggerestablishment of LSPs, reducing the number of LSPs to be established on the LSR and avoiding instabilityof the LSR caused by excessive LSPs.An LSR supports the following types of LSP triggering policies:• Allowing all routing entries to trigger establishment of LSPs.• Filtering routing entries by an IP prefix list, so static and IGP routes denied by the IP prefix list do nottrigger LSP establishment. To use this policy, first create the IP prefix list. For information about IPprefix list configuration, see Layer 3—IP Routing Configuration Guide.To configure the policy for triggering LSP establishment:Step Command Remarks1. Enter system view. system-view N/A2. Enter MPLS view. mpls N/A3. Configure the LSPestablishment triggeringpolicy.lsp-trigger [ vpn-instancevpn-instance-name ] { all | ip-prefixprefix-name }Optional.By default, only host routes with32-bit masks can triggerestablishment of LSPs.If the vpn-instancevpn-instance-name option isspecified, the command configuresan LSP establishment triggeringpolicy for the specified VPN.Otherwise, the commandconfigures an LSP establishmenttriggering policy for the publicnetwork routes.NOTE:For an LSP to be established, an exactly matching routing entry must exist on the LSR. For example, on anLSR, to establish an LSP to a loopback address with a 32-bit mask, there must be an exactly matching hostrouting entry on the LSR.Configuring the label distribution control modeWith the label re-advertisement function enabled, an LSR periodically looks for FECs not assigned withlabels, assigns labels to them if any, and advertises the label-FEC bindings. You can set the labelre-advertisement interval as needed.
