Configure OSPFv3 Graceful Restart Helper

Access global configuration mode.
```
device# configure terminal
```
Enter IPv6 OSPF router configuration mode.
```
device(config)# ipv6 router ospf
```

To disable graceful restart helper, run the following command.

device(config-ipv6-router-ospf-vrf-default-vrf)# no graceful-restart helper

To re-enable graceful restart, run the following command.

device(config-ipv6-router-ospf-vrf-default-vrf)# graceful-restart helper