Ospf Concepts; Configuring Ospf - Siemens RX1500 User Manual

RUGGEDCOM ROX II
User Guide
used to pick the winner. Keeping the ID fixed will avoid any unexpected changes in the election of the
master router.
NOTE
In complex legacy networks, RIP, OSPF, BGP and IS-IS may all be active on the same router at the
same time. Typically, however, only one dynamic routing protocol is employed at one time.
The following sections describe how to configure and manage OSPF:
• Section 5.21.1, "OSPF Concepts"
• Section 5.21.2, "Configuring OSPF"
• Section 5.21.3, "Viewing the Status of Dynamic OSPF Routes"
• Section 5.21.4, "Managing Prefix Lists and Entries"
• Section 5.21.5, "Managing Areas"
• Section 5.21.6, "Managing Route Maps"
• Section 5.21.7, "Managing Incoming Route Filters"
• Section 5.21.8, "Managing Redistribution Metrics"
• Section 5.21.9, "Managing Routing Interfaces"
• Section 5.21.10, "Managing Message Digest Keys"
Section 5.21.1

OSPF Concepts

When an OSPF configured router starts operating, it issues a hello packet. Routers having the same OSPF Area,
hello-interval and dead-interval timers will communicate with each other and are said to be neighbors.
After discovering its neighbors, a router will exchange Link State Advertisements in order to determine the
network topology.
Every 30 minutes (by default), the entire topology of the network must be sent to all routers in an area.
If the link speeds are too low, the links are too busy or there are too many routes, some routes may fail to get re-
announced and will be aged out.
Splitting the network into smaller areas to reduce the number of routes within an area or reducing the number of
routes to be advertised may help to avoid this problem.
In shared access networks (i.e. routers connected by switches or hubs) a designated router and a backup
designated are elected to receive route changes from subnets in the area. Once a designated router is picked, all
routing state changes are sent to the designated router, which then sends the resulting changes to all the routers.
The election is decided based on the priority assigned to the interface of each router. The highest priority wins. If
the priority is tied, the highest router-id wins.
Section 5.21.2

Configuring OSPF

To configure dynamic routing using the Open Shortest Path First (OSPF) daemon, do the following:
1. Change the mode to Edit Private or Edit Exclusive.
OSPF Concepts
Chapter 5
Setup and Configuration
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