Netgear XCM8806 - 8800 SERIES 6-SLOT CHASSIS SWITCH 사용자 설명서
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Chapter 24. OSPF
NETGEAR 8800 User Manual
Overview
Open Shortest Path First (OSPF) is a link state protocol that distributes routing information
between routers belonging to a single IP domain; the IP domain is also known as an
autonomous system (AS). In a link-state routing protocol, each router maintains a database
describing the topology of the AS. Each participating router has an identical database
maintained from the perspective of that router.
between routers belonging to a single IP domain; the IP domain is also known as an
autonomous system (AS). In a link-state routing protocol, each router maintains a database
describing the topology of the AS. Each participating router has an identical database
maintained from the perspective of that router.
From the link state database (LSDB), each router constructs a tree of shortest paths, using
itself as the root. The shortest path tree provides the route to each destination in the AS.
When several equal-cost routes to a destination exist, traffic can be distributed among them.
The cost of a route is described by a single metric.
itself as the root. The shortest path tree provides the route to each destination in the AS.
When several equal-cost routes to a destination exist, traffic can be distributed among them.
The cost of a route is described by a single metric.
OSPF is an interior gateway protocol (IGP), as is the other common IGP—RIP. OSPF and
RIP are compared in
RIP are compared in
.
Note:
Two types of OSPF functionality are available and each has a
different licensing requirement. One is the complete OSPF
functionality and the other is OSPF Edge Mode, a subset of OSPF
that is described below. See
functionality and the other is OSPF Edge Mode, a subset of OSPF
that is described below. See
for specific information regarding OSPF licensing.
OSPF Edge Mode
OSPF Edge Mode is a subset of OSPF available on platforms with an Advanced Edge
license. There are two restrictions on OSPF Edge Mode:
license. There are two restrictions on OSPF Edge Mode:
•
At most, four Active OSPF VLAN interfaces are permitted. There is no restriction on the
number of Passive interfaces.
•
The OSPF Priority on VLANs is 0, and is not configurable. This prevents the system from
acting as a DR or BDR
acting as a DR or BDR
Link State Database
Upon initialization, each router transmits a link state advertisement (LSA) on each of its
interfaces. LSAs are collected by each router and entered into the LSDB of each router. After
all LSAs are received, the router uses the LSDB to calculate the best routes for use in the IP
routing table. OSPF uses flooding to distribute LSAs between routers. Any change in routing
information is sent to all of the routers in the network. All routers within an area have the
exact same LSDB.
interfaces. LSAs are collected by each router and entered into the LSDB of each router. After
all LSAs are received, the router uses the LSDB to calculate the best routes for use in the IP
routing table. OSPF uses flooding to distribute LSAs between routers. Any change in routing
information is sent to all of the routers in the network. All routers within an area have the
exact same LSDB.
describes LSA type numbers.