Ursalink UR51 Industrial Cellular Router User Guide

UR51 User Guide
4.2.7.3 OSPF
OSPF, short for Open Shortest Path First, is a link status based on interior gateway protocol
developed by IETF.
If a router wants to run the OSPF protocol, there should be a Router ID that can be manually
configured. If no Router ID configured, the system will automatically select an IP address of
interface as the Router ID. The selection order is as follows:
- If a Loopback interface address is configured, then the last configured IP address of
Loopback interface will be used as the Router ID;
- If no Loopback interface address is configured, the system will choose the interface with
the biggest IP address as the Router ID.
Five types of packets of OSPF:
- Hello packet
- DD packet (Database Description Packet)
- LSR packet (Link-State Request Packet)
- LSU packet (Link-State Update Packet)
- LSAck packet (Link-Sate Acknowledgment Packet)
-
Neighbor and Neighboring
After OSPF router starts up, it will send out Hello Packets through the OSPF interface. Upon
receipt of Hello packet, OSPF router will check the parameters defined in the packet. If it’s
consistent, a neighbor relationship will be formed. Not all matched sides in neighbor
relationship can form the adjacency relationship. It is determined by the network type. Only
when both sides successfully exchange DD packets and LSDB synchronization is achieved, the
adjacency in the true sense can be formed. LSA describes the network topology around a
router, LSDB describes entire network topology.
Figure 4-2-7-4
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