Figure 3-1 Ospf Router Type - Zte ZXR10 5900E Series Configuration Manual

ZXR10 5900E Series Configuration Guide (IPv4 Routing)
Router Priority and DR Election
Every interface has its own priority on router, which affects the capability of the router to
become a DR or BDR on the network. The priority of router interface is expressed by an
eight-bit unsigned integer, ranging from 0 to 255 (the default value is "1").
In DR election, the interface priorities are compared at first. The router with the highest
priority becomes a DR in the network segment. If the priorities of two routers are the same,
the router which router id is the largest will become a DR. The router which priority is 0
cannot be a DR or BDR.
DR is a concept used in network segment, which is based on router interface. That is,
a router can be a DR on its an interface, and it can be BDR or DROther on its another
interface.
OSPF Area
To reduce the information size that each router stores and maintains and shield the range
that network changing influences on, OSPF divides a network into some minor parts.
Each router must have the complete information of the area where it locates. Area
Border Router (ABR) is used to transmit routing information between different areas. The
information is shared by areas. The routing information can be filtered on area edge,
which reduces the routing information stored in routers.
An area is identified with 32-bit unsigned number. Area 0 is reserved to identify backbone
network, and all other areas must be connected to area 0. The backbone area of OSPF
network has to be continuous. Routers can be one or multiple of the following types
according to its tasks in the area, as shown in

Figure 3-1 OSPF Router Type

l Internal router
All interfaces of the router belong to the same OSPF area. An internal router only
generates a Router LSA and saves a Link-state Database (LSDB).
SJ-20150114102049-003|2015-01-15 (R1.0)
Figure 3-1.
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