Datasheet

13-10
Cisco ONS 15454 SDH Reference Manual, R7.0
October 2008
Chapter 13 Management Network Connectivity
13.2.6 Scenario 6: Using OSPF
13.2.6 Scenario 6: Using OSPF
Open Shortest Path First (OSPF) is a link state Internet routing protocol. Link state protocols use a “hello
protocol” to monitor their links with adjacent routers and to test the status of their links to their
neighbors. Link state protocols advertise their directly connected networks and their active links. Each
link state router captures the link state “advertisements” and puts them together to create a topology of
the entire network or area. From this database, the router calculates a routing table by constructing a
shortest path tree. Routes are continuously recalculated to capture ongoing topology changes.
ONS 15454 SDH nodes use the OSPF protocol in internal ONS 15454 SDH networks for node discovery,
circuit routing, and node management. You can enable OSPF on the ONS 15454 SDH nodes so that the
ONS 15454 SDH topology is sent to OSPF routers on a LAN. Advertising the ONS 15454 SDH network
topology to LAN routers eliminates the need to enter static routes for ONS 15454 SDH subnetworks
manually.
OSPF divides networks into smaller regions, called areas. An area is a collection of networked end
systems, routers, and transmission facilities organized by traffic patterns. Each OSPF area has a unique
ID number, known as the area ID. Every OSPF network has one backbone area called “area 0.” All other
OSPF areas must connect to area 0.
When you enable an ONS 15454 SDH OSPF topology for advertising to an OSPF network, you must
assign an OSPF area ID to the ONS 15454 SDH network. Coordinate the area ID number assignment
with your LAN administrator. All DCC-connected ONS 15454 SDH nodes should be assigned the same
OSPF area ID.
Figure 13-8 shows a network enabled for OSPF.