Advertised Loopback Address
Ex.: 172.16.17.5
??? Used for OSPF router ID.
??? Uses address space.
??? Can be used to remotely
administer router.
Network
172.16.0.0
Introducing OSPF 147
Table 4-2 describes the signi?¬?cant ?¬?elds shown in the show ip route display.
Gateway of last resort is 10.119.254.240 to network 10.140.0.0
O 10.110.0.0 [110/5] via 10.119.254.6, 0:01:00, Ethernet2
O IA 10.67.10.0 [110/10] via 10.119.254.244, 0:02:22, Ethernet2
O 10.68.132.0 [110/5] via 10.119.254.6, 0:00:59, Ethernet2
O 10.130.0.0 [110/5] via 10.119.254.6, 0:00:59, Ethernet2
O E2 10.128.0.0 [170/10] via 10.119.254.244, 0:02:22, Ethernet2
Table 4-2 IP Routing Table Fields
Value Description
O This ?¬?eld indicates the learning method that derived the route. It can be one of
the following values:
I: IGRP1-derived
R: RIP2-derived
O: OSPF-derived (the value displayed in the example)
C: Connected
S: Static
E: EGP3-derived
B: BGP4-derived
D: EIGRP5-derived
EX: EIGRP external
i: IS-IS6-derived
ia: IS-IS
M: Mobile
P: Periodic downloaded static route
U: Per-user static route
o: On-demand routing
Example 4-1 Displaying Routes Known by Router (Continued)
continues
148 Chapter 4: Single-Area OSPF Implementation
1 IGRP = Interior Gateway Routing Protocol
2 RIP = Routing Information Protocol
3 EGP = Exterior Gateway Protocol
4 BGP = Border Gateway Protocol
5 EIGRP = Enhanced Interior Gateway Routing Protocol
6 IS-IS = Intermediate System-to-Intermediate System
Use the show ip ospf command to verify the OSPF router ID.
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