Information Technology Reference
In-Depth Information
Now, the OSPF database and routing table are significantly reduced in Router 7, from seven
OSPF routes to one OSPF route in the
show ip route
output. Also, the default gateway has only
one summary network LSA. Example 8-18 displays the link-state database and routing table.
Example 8-18
Link-State Database and Routing Table for a Totally Stubby Area
Router7#sh ip ospf database
OSPF Router with ID (192.16.100.5) (Process ID 100)
Summary Net Link States (Area 10)
Link ID ADV Router Age Seq# Checksum
0.0.0.0 192.16.100.4 460 0x80000001 0x9371
Router7#sh ip ro
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is 192.16.100.245 to network 0.0.0.0
192.16.100.0/24 is variably subnetted, 3 subnets, 3 masks
C 192.16.100.128/27 is directly connected, Ethernet0
C 192.16.100.244/30 is directly connected, Serial0.1
C 192.16.100.5/32 is directly connected, Loopback0
O*IA 0.0.0.0/0 [110/65] via 192.16.100.245, 00:00:09, Serial0.1
Depending upon the configuration of the network and the number of external routes injected
into the OSPF AS, stub areas might not add much benefit to the configuration, although totally
stubby areas can have a large effect.
OSPF Summary
The characteristics of OSPF are summarized as follows:
•
Link-state routing protocol.
•
Uses IP protocol 89.
•
Classless Protocol (supports VLSMs).
•
Metric is cost (based on interface bandwidth) by default.
•
Sends partial route updates only when there are changes.
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