Allied Telesis AR700 SERIES Software Release 2.7.1 - Manual (Page 105)

105
Software Release 2.7.1
C613-02047-00 REV A
To interpret output from the SHOW RSVP INTERFACE command see the
Resource Reservation Protocol (RSVP) chapter in the Software Reference.
OSPF
Open Shortest Path First (OSPF) is an Internal Gateway Routing Protocol,
based on Shortest Path First (SPF) or link-state technology. OSPF is a routing
protocol that determines the best path for routing IP traffic over a TCP/IP
network.
These features are supported by OSPF:
■ Authentication of routing updates.
■ Tagging of externally-derived routes.
■ Fast response to topology changes with low overhead.
■ Load sharing over meshed links.
OSPF supports three types of physical networks—point-to-point, broadcast
and non-broadcast.
When using OSPF to route an IP packet, the router looks up the routing table
entry which best matches the destination of the packet. This routing table entry
contains the interface and nexthop router to forward the IP packet to its
destination. The routing table entry that best matches the destination is
determined first by the path type, then the longest (most specific) network
mask. At this point there may still be multiple routing entries to the
destination; if so then equi-cost multi-path routes exist to the destination. Such
equi-cost routes are appropriately used to share the load to the destination.
Configuring a Basic OSPF Network
This example ( Figure 20 ) is a simple network of two routers connected
together, each with its own local area network. The routers all belong to a
single class B network 172.31.0.0, which has further been subnetted using the
subnet mask 255.255.255.0.
Figure 20: .A basic OSPF network with an addressless PPP link.
UGOSPF1_R
LAN LAN
Point-to-Point link
172.31.2.1 172.31.2.2
172.31.108.10
Router 2 Router 1
172.31.1.1
Area 1