Verifying OSPF Operation

After you enable OSPF routing on each of the three routers, verify its operation using show commands, as demonstrated in Example 2-10.

Example 2-10 Verifying OPSFRouting

Neo#show ip protocols

Routing Protocol is "ospf 100

Sending updates every 0 seconds

Invalid after 0 seconds, hold down 0, flushed after 0

Outgoing update filter list

for

all interfaces is

Incoming update filter list

for

all interfaces is

Redistributing: ospf 100

Routing for Networks:

10.0.0.0/25

192.168.254.0

201.0.0.0/25

Routing Information Sources

Gateway Distance

Last Update

192.168.254.84 110

03:09:43

192.168.254.83 110

03:09:43

Distance: (default is 110)

With this command output, you can gain some useful data regarding the operation of OSPF in your network. You can see the networks that OSPF is routing as well the RIDs of the other routers in the network that have sent routing information. The output from the show ip ospf command, as demonstrated in Example 2-11, displays more specific information regarding how OSPF is running on the router that the command is executed on.

Example 2-11 Output from the show ip ospf Command

Neo#show ip ospf Routing Process "ospf 100" with ID 192.168.254.82 Supports only single TOS(TOS0) routes Supports opaque LSA It is an area border router

SPF schedule delay 5 sees, Hold time between two SPFs 10 sees Minimum LSA interval 5 sees. Minimum LSA arrival 1 sees Number of external LSA 0. Checksum Sum 0x0 Number of opaque AS LSA 0. Checksum Sum 0x0 Number of DCbitless external and opaque AS LSA 0 Number of DoNotAge external and opaque AS LSA 0 Number of areas in this router is 2. 1 normal 1 stub 0 nssa External flood list length 0 Area BACKBONE(0)

Number of interfaces in this area is 2 Area has no authentication SPF algorithm executed 15 times Area ranges are

Number of LSA 4. Checksum Sum 0x158A8 Number of opaque link LSA 0. Checksum Sum 0x0 Number of DCbitless LSA 0 Number of indication LSA 0

continues

98 Chapter 2: Introduction to OSPF

Example 2-11 Output from the show ip ospf Command (Continued)

Number of DoNotAge LSA 0 Flood list length 0 Area 201

Number of interfaces in this area is 1 It is a stub area generates stub default route with cost 1 Area has no authentication SPF algorithm executed 7 times Area ranges are

100.0.0.0/16 Passive Advertise 201.0.0.0/16 Passive Advertise Number of LSA 6. Checksum Sum 0x42B44 Number of opaque link LSA 0. Checksum Sum 0x0 Number of DCbitless LSA 0 Number of indication LSA 0 Number of DoNotAge LSA 0 Flood list length 0

This show command provides a wealth of OSPF information and how OSPF is operating on the router that it is executed on. Through this command, you see what the RID is for OSPF (192.168.254.82), which is the loopback interface's IP address that you configured earlier in Example 2-8. You can also see what kind of OSPF router it is (for example, an ABR). You can also see how many times the SPF algorithm has run per area (recall that OSPF calculates the LSDB on a per-area basis).

On the router you are evaluating, you want to find out what the router knows about OSPF on other routers and the network in general. The next set of commands reference the neighbors and what router (Neo) has learned about them. Example 2-12 provides information about the neighboring routers using the show ip ospf neighbor command.

Example 2-12 Displaying Neighboring Router OSPF Information

Neo#show ip

ospf neighbor

Neighbor ID

Pri

State

Dead Time

Address

Interface

192.168.254

83 1

FULL/DROTHER

00:00:38

10.0.0.1

FastEthernet0/0

192.168.254

84 1

FULL/BDR

00:00:37

10.0.0.2

FastEthernet0/0

Neo#

In this output, you can see the following:

• RIDs of Neo's neighboring routers

• State of communication each is in (more on that in Chapter 3)

• IP address on the neighbor router from which Neo received the OSPF communication

• Receiving interface

This is useful information when you are working with networks that have large numbers of neighbors. Now look at the State column. As previously mentioned, Neo is communicating to each neighbor, as represented by the FULL status. The other part of the State column indicates the role that router is playing. In other words, the 192.168.254.84 neighbor is the BDR for the network, and neighbor 192.168.254.83 says it is DROTHER (that is, DR other). Can you guess which of the three routers is the DR? The results of the show ip ospf neighbor detail command in Example 2-13 tells you if you guessed correctly.

Example 2-13 Displaying Detailed Neighboring Router OSPF Information

Neo#show ip ospf neighbor detail

Neighbor 192.168.254.83, interface address 10.0.0.1 In the area 0 via interface FastEthernet0/0 Neighbor priority is 1, State is FULL, 6 state changes DR is 10.0.0.3 BDR is 10.0.0.2 Options is 0x2 Dead timer due in 00:00:33

Index 2/2, retransmission queue length 0, number of retransmission 2 First 0x0(0)/0x0(0) Next 0x0(0)/0x0(0) Last retransmission scan length is 1, maximum is 1 Last retransmission scan time is 0 msec, maximum is 0 msec Neighbor 192.168.254.84, interface address 10.0.0.2 In the area 0 via interface FastEthernet0/0 Neighbor priority is 1, State is FULL, 6 state changes DR is 10.0.0.3 BDR is 10.0.0.2 Options is 0x2 Dead timer due in 00:00:39

Index 1/1, retransmission queue length 0, number of retransmission 1

Last retransmission scan length is 1, maximum is 1

Last retransmission scan time is 0 msec, maximum is 0 msec

Neo#

The show ip ospf neighbor detail command provides all the data needed to analyze the communication between OSPF neighbor routers. Notice that this command identifies the DR and BDR for the network and shows all the information regarding the various OSPF timers.

The show ip ospf interface command is one of the most descriptive regarding the status of the network. With this command, you can determine how OSPF is operating on the interface it is run on and what those operational parameters are. Because each interface on a given router is connected to a different network, some of the key OSPF information is interface-specific. Example 2-14 demonstrates sample output from this command.

100 Chapter 2: Introduction to OSPF

Example 2-14 Output from the show ip ospf interface Command

Neo#show ip ospf interface fa0/0

FastEthernet0/0 is up, line protocol is up Internet Address 10.0.0.3/25, Area 0

Process ID 100, Router ID 192.168.254.82, Network Type BROADCAST, Cost: 1 Transmit Delay is 1 sec, State DR, Priority 1

Designated Router (ID) 192.168.254.82, Interface address 10.0.0.3 Backup Designated router (ID) 192.168.254.84, Interface address 10.0.0.2 Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5

Hello due in 00:00:09 Index 1/1, flood queue length 0 Next 0x0(0)/0x0(0)

Last flood scan length is 0, maximum is 3 Last flood scan time is 0 msec, maximum is 0 msec Neighbor Count is 2, Adjacent neighbor count is 2 Adjacent with neighbor 192.168.254.83

Adjacent with neighbor 192.168.254.84 (Backup Designated Router) Suppress hello for 0 neighbor(s) Neo#

The final command discussed in this chapter is the show ip ospf database command. You have seen how the LSDB is formed and the role that it plays in developing the routing table in an OSPF network. Example 2-15 demonstrates how the LSDB is represented in a Cisco router.

Example 2-15 Output from the show ip ospf database Command

Neo#show ip ospf database

OSPF Router with ID (192.168.254.82) (Process ID 100)

Router Link States (Area 0)

Link ID ADV Router Age Seq# Checksum Link count

192.168.254.82 192.168.254.82 1696 0x80000013 0x6A5A 2

192.168.254.83 192.168.254.83 1943 0X8000000D 0X4E71 2

192.168.254.84 192.168.254.84 1675 0X8000000D 0X5F5D 2

Net Link States (Area 0)

Link ID ADV Router Age Seq# Checksum

10.0.0.3 192.168.254.82 1951 0X8000000B 0x2090

Router Link States (Area 201)

Link ID ADV Router Age Seq# Checksum Link count

192.168.254.82 192.168.254.82 423 0X8000000F 0XD1EE 0

Example 2-15 Output from the show ip ospf database Command (Continued)

Summary Net Link States (Area 201)

Link ID

192.168.254.82

192.168.254.83

192.168.254.84

ADV Router Age Seq# Checksum

192.168.254.82 1178 0x8000000C 0xA8CF

192.168.254.82 1953 0x80000011 0x1FC9

192.168.254.82 1698 0x8000000B 0xCCF1

192.168.254.82 1953 0x8000000B 0xCCEF

192.168.254.82 1698 0x8000000B 0xC2F8

This command presents which LSDB to use based on area and LSA type; more discussion is presented in Chapter 3. However, you can see that each link is represented.

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