Avaya ERS 8600 series, Configuration Manual

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Router Type Description
routers on the network synchronize and advertise that network
to the remainder of the AS.
Backup designated router
(BDR) A backup designated router (BDR) is elected in addition to the
designated router (DR) and becomes the DR if required.
OSPF interfaces
An OSPF interface, or link, is configured on an IP interface. In the Avaya Ethernet Routing
Switch 8800/8600, an IP interface can be a single link (brouter port) or a logical interface
configured on a VLAN (multiple ports). The underlying lower level protocols and the routing
protocol itself obtain the state information associated with the interface.
The Avaya Ethernet Routing Switch 8800/8600 designates OSPF interfaces as one of the
following types:
• broadcast (active)
• nonbroadcast multiaccess (NBMA)
• point-to-point
• point-to-multipoint
Important:
When you enable an OSPF interface, you cannot change the interface type. You must first
disable the interface. You can then change the type and reenable the interface. For an NMBA
interface, you must also first delete the manually configured neighbors.
This section contains the following topics:
• Broadcast interface on page 41
• Nonbroadcast multiaccess interface on page 41
Broadcast interface
Broadcast interfaces support many attached routers and can address a single physical
message to all attached broadcast routers (sent to AllSPFRouters and AllDRouters).
Broadcast interfaces discover neighboring routers dynamically using the OSPF Hello Protocol.
Each pair of routers on a broadcast network, such as an Ethernet, communicate directly.
Nonbroadcast multiaccess interface
Nonbroadcast multiaccess (NBMA) interfaces support many routers but cannot broadcast.
In contrast to a broadcast network where some OSPF protocol packets are multicast (sent to
AllSPFRouters and AllDRouters), NBMA interfaces replicate and send OSPF packets to each
neighboring router, in turn, as unicast. NBMA networks drop all OSPF packets with destination
addresses to AllSPFRouters and AllDRouters.
Routing
Configuration — IPv6 Routing November 2010 41