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DES-7200 Configuration Guide Chapter 3 MPLS Reliability Configuration
3-17
PE1 sends Open message carrying GR-Capable <AFI=IPv4, SAFI=Unicast> and <AFI=IPv4,
SAFI=VPNv4> to PE2 in order to establish GR-Capable iBGP Session. When the main
management board works normally, the main management board will need to backup GR
information to the slave management board, so that these raw data can be read and used for
protocol GR after main-slave management board switchover.
z During main-slave management board switchover
The GR information of PE1 has been backuped to the slave management board. Its main task at
this phase is to carry out main-slave management board switchover.
P device detects that the corresponding TCP session has entered into "Down" state and then
marks the corresponding LSP as "stale". Meanwhile, it will start forwarding table aging timer and
keep forwarding packets before the timer runs out.
When PE2 detects that the TCP connection is disconnected, it will immediately mark the routes
learned from PE1 as "stale" and start a restart timer against PE1. Before the restart timer runs
out, if Open message is still not received, it will remove the "stable" route tag marked recently. If
Open message is received, it will delete the restart timer. During this period, PE1 and PE2 will
use the original route to forward traffic.
z After main-slave management board switchover
On PE1, the slave management board becomes the new main management board, and the main
management board becomes the new slave management board. On the new main management
board, the device will check the backuped GR information to see whether forwarding data before
the restart is retained. After that, the device will begin CLI configuration initialization and GR.
During the GR of IGP, BGP and LDP, they will advertise all IGP protocol neighbors, BGP
neighbors and LDP neighbors to re-establish connection.
¾ IGP convergence
PE1 sends GR-Capable Initialization message to the neighboring P device and re-establish
session to acquire topology and routing information after receiving response. PE1 will then
recalculate the routing table and delete "stable" routes to complete protocol convergence.
¾ BGP processing
PE1 and CE will exchange routing information. After that, PE1 will update the routing table and
forwarding data according to the new routes, replace void routing information and complete BGP
protocol convergence.
PE1 and PE2 began to rebuild BGP session. Firstly, it sends Open message (carrying
GR-Capable parameters) to PE2; secondly, it receives and handles the Update messages