References For Ospf; Ospf Functional Overview - Cisco NCS 5500 Series Configuration Manuals

Implementing OSPF
Displays OSPF interface information.
Example
The following is sample output that displays the GTSM security TTL value configured on an OSPF
interface:
show ospf 1 interface
TenGigE0/5/0/0 is up, line protocol is up

References for OSPF

To implement OSPF you need to understand the following concepts:

OSPF Functional Overview

OSPF is a routing protocol for IP. It is a link-state protocol, as opposed to a distance-vector protocol. A
link-state protocol makes its routing decisions based on the states of the links that connect source and destination
machines. The state of the link is a description of that interface and its relationship to its neighboring networking
devices. The interface information includes the IP address of the interface, network mask, type of network to
which it is connected, routers connected to that network, and so on. This information is propagated in various
types of link-state advertisements (LSAs).
A router stores the collection of received LSA data in a link-state database. This database includes LSA data
for the links of the router. The contents of the database, when subjected to the Dijkstra algorithm, extract data
to create an OSPF routing table. The difference between the database and the routing table is that the database
contains a complete collection of raw data; the routing table contains a list of shortest paths to known
destinations through specific router interface ports.
OSPF is the IGP of choice because it scales to large networks. It uses areas to partition the network into more
manageable sizes and to introduce hierarchy in the network. A router is attached to one or more areas in a
network. All of the networking devices in an area maintain the same complete database information about the
TenGigE0/5/0/0
Internet Address 120.10.10.1/24, Area 0
Process ID 1, Router ID 100.100.100.100, Network Type BROADCAST, Cost: 1
Transmit Delay is 1 sec, State BDR, Priority 1
TTL security enabled, hop count 2
Designated Router (ID) 102.102.102.102, Interface address 120.10.10.3
Backup Designated router (ID) 100.100.100.100, Interface address 120.10.10.1
Flush timer for old DR LSA due in 00:02:36
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 00:00:05
Index 1/1, flood queue length 0
Next 0(0)/0(0)
Last flood scan length is 1, maximum is 4
Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 1, Adjacent neighbor count is 1
Adjacent with neighbor 102.102.102.102
Suppress hello for 0 neighbor(s)
Multi-area interface Count is 0
Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 6.3.x
(Designated Router)
References for OSPF
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