(Optional) Configuring MPLS LDP Timers
- Tracy Yang
LDP uses the discovery process to identify other LDP-enabled routers in the network. The discovery process involves sending "Hello" messages, which can be of two types:
Link Hello: These are sent to directly connected neighbors over a specific interface.
Targeted Hello: These are sent to establish sessions with non-directly connected peers.
Configure the Link Hello Sending Timer
NOTEs：
Before configuring the discovery hello-interval and discovery hello-holdtime, the discovery transport-address under the IP family must be configured first.
The configuration of discovery hello-interval and discovery hello-holdtime based on the IP family takes precedence over the global configuration.
For the discovery hello-interval (discovery hello-holdtime) configuration, the actual effective timer value equals the smaller of the timers configured on both ends of the LDP peers.
The LSR uses the Hello interval to periodically send Hello messages, notifying neighboring LSRs of its presence in the network and establishing Hello adjacency relationships. The value is an integer which can be configured between 1 and 65535 seconds. The default value is 5 seconds.
Configure the interval for sending Hello message.
admin@PICOS# set protocols mpls ldp ipv4-family discovery hello-interval 10
admin@PICOS# commitConfigure the Link Hello Hold Time
LDP peers that have established a Hello adjacency relationship periodically send Hello messages to signify their intention to maintain this adjacency. If no new Hello message is received before the Hello hold timer expires, the adjacency will be terminated. The value is an integer which can be configured between 1 and 65535 seconds. The default value is 15 seconds. It is recommended to use the default value.
Configure the Hello hold time.
admin@PICOS# set protocols mpls ldp ipv6-family discovery hello-holdtime 30
admin@PICOS# commitShow the configuration result.
admin@PICOS# run show mpls ldp interface
AF Interface State Uptime Hello Timers ac
ipv6 vlan10 ACTIVE 3d18h21m 5/30 1
ipv6 vlan20 ACTIVE 3d18h21m 5/30 1
ipv6 vlan30 ACTIVE 01:02:58 5/30 1
ipv6 vlan40 ACTIVE 00:48:21 5/30 0Configure the Hold Time Period for Keepalive
Between LDP peers, LDP sessions are maintained through LDP protocol messages (PDUs). If the Keepalive hold timer expires without receiving any LDP PDUs, the connection is closed, and the LDP session ends. That value is an integer which can be configured between 15 and 65535 seconds. By default, LDP session holdtime 180 seconds.
The Keepalive sent interval is the time for the LSR to periodically send Hello messages, and it is 1/3 of the Keepalive hold timer.
Configure the hold time period for keepalive.
admin@PICOS# set protocols mpls ldp neighbor 3.3.3.3 session-holdtime 210
admin@PICOS# commitShow the configuration result.
admin@PICOS# run show mpls ldp neighbor detail
Peer LDP Identifier: 3.3.3.3:0
TCP connection: 2::2:646 - 3::3:34795
Authentication: none
Session Holdtime: 210 secs; KeepAlive interval: 70 secs
State: OPERATIONAL; Downstream-Unsolicited
Up time: 2d19h07m
Messages sent/rcvd:
- Keepalive Messages: 4022/4024
- Address Messages: 1/3
- Address Withdraw Messages: 3/3
- Notification Messages: 0/0
- Capability Messages: 0/0
- Label Mapping Messages: 128/70
- Label Request Messages: 0/0
- Label Withdraw Messages: 16/10
- Label Release Messages: 10/16
- Label Abort Request Messages: 0/0
Capabilities Sent:
- Dynamic Announcement (0x0506)
- Typed Wildcard (0x050B)
- Unrecognized Notification (0x0603)
Capabilities Received:
- Dynamic Announcement (0x0506)
- Typed Wildcard (0x050B)
- Unrecognized Notification (0x0603)
LDP Discovery Sources:
IPv6:
Interface: vlan30Configure the Interval for Sending Targeted Hello Messages
NOTEs：
Before configuring the discovery targeted-hello-interval and discovery targeted-hello-holdtime, the targeted-hello-accept under the IP family must be enabled first.
The configuration of discovery targeted-hello-interval and discovery targeted-hello-holdtime based on the IP family takes precedence over the global configuration.
For the targeted-hello-holdtime (discovery targeted-hello-interval) configuration, the actual effective timer value equals the smaller of the timers configured on both ends of the LDP peers.
Users can set the interval (in seconds) at which the targeted Hello messages are sent out to maintain LDP sessions with non-directly connected peers. A shorter interval means more frequent Hellos, which can help in quicker detection of peers but may increase the load on the router.
The value is an integer which can be configured between 1 and 65535 seconds. The default value is 5 seconds.
Configure the interval for sending targeted hello messages.
admin@PICOS# set protocols mpls ldp discovery targeted-hello-interval 10
admin@PICOS# commitConfigure the Targeted Hello Hold Time
The targeted-hello-holdtime parameter sets the amount of time (in seconds) that the router will wait after receiving the last Hello message before considering the neighbor as unreachable. If the router does not receive another Hello message from the neighbor within this period, it will consider the neighbor to be down and will tear down the LDP session associated with that neighbor.
This timer ensures that the LDP session is maintained as long as the neighbor is responsive. It is a fail-safe mechanism that helps in quickly detecting and reacting to network changes.
The value is an integer which can be configured between 1 and 65535 seconds. The default value is 15 seconds.
Administrators can adjust this value to either lengthen or shorten the period before the router considers the neighbor unreachable. A shorter hold time means the router will more quickly declare the neighbor down if no Hello messages are received, while a longer hold time will delay this declaration, potentially allowing more time for transient issues to resolve.
Configure the targeted hello hold time.
admin@PICOS# set protocols mpls ldp discovery targeted-hello-holdtime 50
admin@PICOS# commitCopyright © 2024 Pica8 Inc. All Rights Reserved.