Netgear XCM8810 - 8800 SERIES 10-SLOT CHASSIS SWITCH ユーザーズマニュアル
Chapter 24. OSPF
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NETGEAR 8800 User Manual
able to inform its neighbors in advance that OSPF is restarting. An unplanned restart would
occur if there was some kind of system failure that caused a remote reboot or a crash of
OSPF, or an MSM/MM failover occurs. As OSPF restarts, it informs its neighbors that it is in
the midst of an unplanned restart. You can decide to configure a router to enter graceful
restart for only planned restarts, for only unplanned restarts, or for both. Also, you can
separately decide to configure a router to be a helper for only planned, only unplanned, or for
both kinds of restarts.
occur if there was some kind of system failure that caused a remote reboot or a crash of
OSPF, or an MSM/MM failover occurs. As OSPF restarts, it informs its neighbors that it is in
the midst of an unplanned restart. You can decide to configure a router to enter graceful
restart for only planned restarts, for only unplanned restarts, or for both. Also, you can
separately decide to configure a router to be a helper for only planned, only unplanned, or for
both kinds of restarts.
Configuring Graceful OSPF Restart
To configure a router to perform graceful OSPF restart, use the following command:
configure ospf restart [none | planned | unplanned | both]
Since a router can act as a restart helper router to multiple neighbors, you will specify which
neighbors to help. To configure a router to act as a graceful OSPF restart helper, use the
following command:
neighbors to help. To configure a router to act as a graceful OSPF restart helper, use the
following command:
configure ospf [vlan [all | <vlan-name>] | area <area-identifier> |
virtual-link <router-identifier> <area-identifier>] restart-helper [none |
planned | unplanned | both]
The graceful restart period sent out to helper routers can be configured with the following
command:
command:
configure ospf restart grace-period <seconds>
By default, a helper router will terminate graceful restart if received LSAs would affect the
restarting router. This will occur when the restart-helper receives an LSA that will be flooded
to the restarting router or when there is a changed LSA on the restarting router's
retransmission list when graceful restart is initiated. To disable this behavior, use the
following command:
restarting router. This will occur when the restart-helper receives an LSA that will be flooded
to the restarting router or when there is a changed LSA on the restarting router's
retransmission list when graceful restart is initiated. To disable this behavior, use the
following command:
disable ospf [vlan [all | <vlan-name>] | area <area-identifier> | virtual-link
<router-identifier> <area-identifier>] restart-helper-lsa-check
Areas
OSPF allows parts of a network to be grouped together into areas. The topology within an
area is hidden from the rest of the AS. Hiding this information enables a significant reduction
in LSA traffic and reduces the computations needed to maintain the LSDB. Routing within the
area is determined only by the topology of the area.
area is hidden from the rest of the AS. Hiding this information enables a significant reduction
in LSA traffic and reduces the computations needed to maintain the LSDB. Routing within the
area is determined only by the topology of the area.
The three types of routers defined by OSPF are as follows:
•
Internal router (IR)—An internal router has all of its interfaces within the same area.
•
Area border router (ABR)—An ABR has interfaces in multiple areas. It is responsible for
exchanging summary advertisements with other ABRs.
•
Autonomous system border router (ASBR)—An ASBR acts as a gateway between
OSPF and other routing protocols, or other autonomous systems.