3Com Switch 8800 Advanced Software V5 Configuration Guide

794 CHAPTER 55: GR CONFIGURATION

■ GR Time: The time taken for the GR Restarter and the GR Helper to establish a

session between them. Upon detection of the down state of a neighbor, the

GR Helper will preserve the topology and routing information sent from the GR

Restarter for a period as specified by the GR Time.

Graceful Restart communication procedure

Configure a device as GR Restarter in a network. This device and its GR Helper

must support GR or be GR capable. Thus, when GR Restarter restarts, its GR

Helper can know its restart process.

■ In some cases, GR Restarter and GR Helper can replace with each other.

■ If a router is to act as a Graceful Restarter, it must have the ability to preserve

the routing information in the routing table (forwarding table). Routers that fail

to meet this can only act as a GR Helper.

The communication procedure between the GR Restarter and the GR Helper

works as follows:

1 A GR session is established between the GR Restarter and the GR Helper.

Figure 241 A GR session is established between the GR Restarter and the GR Helper

As illustrated in Figure 241, Router A works as GR Restarter, Router B, Router C

and Router D are the GR Helpers of Router A. A GR session is established between

the GR Restarter and the GR Helper.

2 GR Restarter restarting

GR helper

Router D

Router B

Router C

Router A

GR helper GR helper

GR restarter

GR capable GR session