Table of contents
Chapter 1 OSPF Protocol Features and Configuration
Experiment 1-1 OSPF Single Area
Step 1. Basic configuration and IP addressing
Step 2. Configure OSPF for a single area
Step 3. Observe the process of establishing the adjacency relationship of the router on the Ethernet
Step 4. Configure the network type of the Loopback interface in OSPF
Step 5. Modify the OSPF cost value of the interface
Step 6. Configure OSPF Silent-interface
Additional Experiments: Think and Verify
Chapter 1 OSPF Protocol Features and Configuration
Experiment 1-1 OSPF Single Area
learning purpose
Master the configuration method of single-area OSPF
Master the configuration method of OSPF area authentication
· Understand the process of OSPF establishing neighbor relationships in multi-access networks
Understand the form of OSPF mask distribution for the network connected to the Loopback interface
Master the method of modifying the cost value of OSPF interface
Master the configuration method of Silent-interface in OSPF
Master the method of using Display to view various states of OSPF
Master the method of using the Debug command to view the OSPF adjacency relationship and troubleshoot
Topology
Figure 1-1 OSPF single area
Scenes
You are the company's network administrator. Now there are three ARG3 routers in the company's network, which are connected to each other through Ethernet. On a broadcast multi-access network like Ethernet, there may be security risks, so you choose to use OSPF area authentication to avoid malicious routing attacks. In the process of deploying the network, there is a network connectivity problem. You use the display and debug commands to troubleshoot.
Learning tasks
Step 1. Basic configuration and IP addressing
Configure IP addresses and masks for R1, R2, and R3. During configuration, the configuration mask of the loopback interface is 24 bits, which is simulated as a separate network segment. After the configuration is complete, test the connectivity of the direct link.
<R1>system-view
Enter system view, return user view with Ctrl+Z.
[R1]interface GigabitEthernet 0/0/0
[R1-GigabitEthernet0/0/0]ip address 10.0.123.1 24
[R1-GigabitEthernet0/0/0]quit
[R1]interface LoopBack 0
[R1-LoopBack0]ip address 10.0.1.1 24
[R1-LoopBack0]quit
<R2>system-view
Enter system view, return user view with Ctrl+Z.
[R2]interface GigabitEthernet 0/0/0
[R2-GigabitEthernet0/0/0]ip address 10.0.123.2 24
[R2-GigabitEthernet0/0/0]quit
[R2]interface LoopBack 0
[R2-LoopBack0]ip address 10.0.2.2 24
[R2-LoopBack0]quit
<R3>system-view
Enter system view, return user view with Ctrl+Z.
[R3]interface GigabitEthernet 0/0/0
[R3-GigabitEthernet0/0/0]ip address 10.0.123.3 24
[R3-GigabitEthernet0/0/0]quit
[R3]interface LoopBack 0
[R3-LoopBack0]ip address 10.0.3.3 24
[R3-LoopBack0]quit
After configuring the addresses of the interfaces, verify the connectivity between the routers.
[R1]ping -c 1 10.0.123.2
PING 10.0.123.2: 56 data bytes, press CTRL_C to break
Reply from 10.0.123.2: bytes=56 Sequence=1 ttl=255 time=2 ms
--- 10.0.123.2 ping statistics ---
1 packet(s) transmitted
1 packet(s) received
0.00% packet loss
round-trip min/avg/max = 2/2/2 ms
[R1]ping -c 1 10.0.123.3
PING 10.0.123.3: 56 data bytes, press CTRL_C to break
Reply from 10.0.123.3: bytes=56 Sequence=1 ttl=255 time=2 ms
--- 10.0.123.3 ping statistics ---
1 packet(s) transmitted
1 packet(s) received
0.00% packet loss
round-trip min/avg/max = 2/2/2 ms
[R2]ping -c 1 10.0.123.3
PING 10.0.123.3: 56 data bytes, press CTRL_C to break
Reply from 10.0.123.3: bytes=56 Sequence=1 ttl=255 time=2 ms
--- 10.0.123.3 ping statistics ---
1 packet(s) transmitted
1 packet(s) received
0.00% packet loss
round-trip min/avg/max = 2/2/2 ms
Step 2. Configure OSPF for a single area
Configure single-area OSPF. All routers belonging to area 0 are configured to use OSPF process 1. At the same time, configure regional authentication and use the password "huawei". In the zone, Huawei devices support authentication using plaintext or MD5 values. Here, we only use plaintext for authentication.
Note that when using the network command, use 0.0.0.0 for the wildcard mask. To ensure the stability of the Router ID of the router, we use the router-id parameter to statically specify the Router ID of the router when starting the OSPF process .
[R1]ospf 1 router-id 10.0.1.1
[R1-ospf-1]area 0
[R1-ospf-1-area-0.0.0.0]network 10.0.123.1 0.0.0.0
[R1-ospf-1-area-0.0.0.0]network 10.0.1.1 0.0.0.0
[R1-ospf-1-area-0.0.0.0]authentication-mode simple plain huawei
[R1-ospf-1-area-0.0.0.0]quit
[R1-ospf-1]quit
[R2]ospf 1 router-id 10.0.2.2
[R2-ospf-1]area 0
[R2-ospf-1-area-0.0.0.0]network 10.0.123.2 0.0.0.0
[R2-ospf-1-area-0.0.0.0]network 10.0.2.2 0.0.0.0
[R2-ospf-1-area-0.0.0.0]authentication-mode simple plain huawei
[R2-ospf-1-area-0.0.0.0]quit
[R2-ospf-1]quit
[R3]ospf 1 router-id 10.0.3.3
[R3-ospf-1]area 0
[R3-ospf-1-area-0.0.0.0]network 10.0.123.3 0.0.0.0
[R3-ospf-1-area-0.0.0.0]network 10.0.3.3 0.0.0.0
[R3-ospf-1-area-0.0.0.0]authentication-mode simple plain huawei
[R3-ospf-1-area-0.0.0.0]quit
[R3-ospf-1]quit
After the configuration is complete, check the routing table of the device and test the connectivity of the entire network. We start by looking at the routing table on R1.
[R1]display ip routing-table
Route Flags: R - relay, D - download to fib
----------------------------------------------------------------------------
Routing Tables: Public
Destinations : 12 Routes : 12
Destination/Mask Proto Pre Cost Flags NextHop Interface
10.0.1.0/24 Direct 0 0 D 10.0.1.1 LoopBack0
10.0.1.1/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.1.255/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.2.2/32 OSPF 10 1 D 10.0.123.2 GigabitEthernet0/0/0
10.0.3.3/32 OSPF 10 1 D 10.0.123.3 GigabitEthernet0/0/0
10.0.123.0/24 Direct 0 0 D 10.0.123.1 GigabitEthernet0/0/0
10.0.123.1/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
10.0.123.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
127.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
255.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
From the output, we can see that R1 has learned two routes from OSPF, 10.0.2.2/32 and 10.0.3.3/32, and the next hops are 10.0.123.2 and 10.0.123.3 respectively. Then check the connectivity of the loopback addresses from R1 to R2 and R3 respectively.
[R1]ping -c 1 10.0.2.2
PING 10.0.2.2: 56 data bytes, press CTRL_C to break
Reply from 10.0.2.2: bytes=56 Sequence=1 ttl=255 time=3 ms
--- 10.0.2.2 ping statistics ---
1 packet(s) transmitted
1 packet(s) received
0.00% packet loss
round-trip min/avg/max = 3/3/3 ms
[R1]ping -c 1 10.0.3.3
PING 10.0.3.3: 56 data bytes, press CTRL_C to break
Reply from 10.0.3.3: bytes=56 Sequence=1 ttl=255 time=2 ms
--- 10.0.3.3 ping statistics ---
1 packet(s) transmitted
1 packet(s) received
0.00% packet loss
round-trip min/avg/max = 2/2/2 ms
Run the display ospf brief command to view basic OSPF information running on the router.
[R1]display ospf brief
OSPF Process 1 with Router ID 10.0.1.1
OSPF Protocol Information
RouterID: 10.0.1.1 Border Router:
Multi-VPN-Instance is not enabled
Global DS-TE Mode: Non-Standard IETF Mode
Graceful-restart capability: disabled
Helper support capability : not configured
Applications Supported: MPLS Traffic-Engineering
Spf-schedule-interval: max 10000ms, start 500ms, hold 1000ms
Default ASE parameters: Metric: 1 Tag: 1 Type: 2
Route Preference: 10
ASE Route Preference: 150
SPF Computation Count: 9
RFC 1583 Compatible
Retransmission limitation is disabled
Area Count: 1 Nssa Area Count: 0
ExChange/Loading Neighbors: 0
Process total up interface count: 2
Process valid up interface count: 1
Area: 0.0.0.0 (MPLS TE not enabled)
Authtype: Simple Area flag: Normal
SPF scheduled Count: 9
ExChange/Loading Neighbors: 0
Router ID conflict state: Normal
Area interface up count: 2
Interface: 10.0.1.1 (LoopBack0)
Cost: 0 State: P-2-P Type: P2P MTU: 1500
Timers: Hello 10 , Dead 40 , Poll 120 , Retransmit 5 , Transmit Delay 1
Interface: 10.0.123.1 (GigabitEthernet0/0/0)
Cost: 1 State: DR Type: Broadcast MTU: 1500
Priority: 1
Designated Router: 10.0.123.1
Backup Designated Router: 10.0.123.2
Timers: Hello 10 , Dead 40 , Poll 120 , Retransmit 5 , Transmit Delay 1
From the above output, we can see that plaintext authentication (Authtype: Simple) is enabled in area 0, and two interfaces participate in the operation of OSPF: GigabitEthernet0/0/0 and LoopBack0. Among them, GigabitEthernet0/0/0 is a broadcast network (Broadcast), the cost (Cost) is 1, the priority (Priority) is 1, R1's own role is DR, and the BDR (10.0.123.2) on this network is listed later. The network type of another interface LoopBack0 running OSPF is P2P.
Run the display ospf peer brief command to check the establishment of the OSPF neighbor relationship of the router.
[R1]display ospf peer brief
OSPF Process 1 with Router ID 10.0.1.1
Peer Statistic Information
----------------------------------------------------------------------------
Area Id Interface Neighbor id State
0.0.0.0 GigabitEthernet0/0/0 10.0.2.2 Full
0.0.0.0 GigabitEthernet0/0/0 10.0.3.3 Full
----------------------------------------------------------------------------
Total Peer(s): 2
From the above output, we can see that in area 0.0.0.0, R1 has two neighbors, the router IDs of the neighbors are 10.0.2.2 and 10.0.3.3 respectively, and the status between them is Full.
Run the display ospf lsdb command to check the OSPF database information of the router.
[R1]display ospf lsdb
OSPF Process 1 with Router ID 10.0.1.1
Link State Database
Area: 0.0.0.0
Type LinkState ID AdvRouter Age Len Sequence Metric
Router 10.0.3.3 10.0.3.3 1569 48 80000005 0
Router 10.0.2.2 10.0.2.2 1568 48 80000006 0
Router 10.0.1.1 10.0.1.1 1567 48 80000008 0
Network 10.0.123.110.0.1.1 1567 36 80000004 0
Here we can see a total of 4 LSAs. The first 3 are Type 1 LSAs, generated by R1, R2, and R3 respectively. We can use AdvRouter to determine which router generated the LSA. The fourth is the second type of LSA, which is generated by the DR of a network segment. Here, R1 is the DR of the network segment 10.0.123.0/24, so we can see that the AdvRouter of this LSA is 10.0.1.1.
[R1]display ospf lsdb router self-originate
OSPF Process 1 with Router ID 10.0.1.1
Area: 0.0.0.0
Link State Database
Type : Router
Ls id : 10.0.1.1
Adv rtr : 10.0.1.1
Ls age : 430
Len : 48
Options : E
seq# : 80000009
chksum : 0x8188
Link count: 2
* Link ID: 10.0.1.1
Data : 255.255.255.255
Link Type: StubNet
Metric : 0
Priority : Medium
* Link ID : 10.0.123.1
Data : 10.0.123.1
Link Type: TransNet
Metric : 1
The above output is the detailed information of the Router LSA generated by R1. We can see that this LSA describes a total of 2 networks. The first network is the network segment where the loopback interface is located, and the link type is StubNet. Link ID and Data are the IP address and mask of the Stub network segment respectively. The second network is the Internet segment of the three routers, the link type is TransNet, you can see that the Link ID is the port address of DR 10.0.123.1, and the Data is the IP address of the local port on the network segment 10.0.123.1;
[R1]display ospf lsdb network self-originate
OSPF Process 1 with Router ID 10.0.1.1
Area: 0.0.0.0
Link State Database
Type : Network
Ls id : 10.0.123.1
Adv rtr : 10.0.1.1
Ls age : 1662
Len : 36
Options : E
seq# : 80000005
chksum: 0x3d58
Net mask : 255.255.255.0
Priority : Low
Attached Router 10.0.1.1
Attached Router 10.0.2.2
Attached Router 10.0.3.3
The above output is the detailed information of the Network LSA generated by R1. We can see that the second type of LSA describes the neighbor information of the network segment where the DR is located.
Step 3. Observe the process of establishing the adjacency relationship of the router on the Ethernet
First check the DR and BDR elections in the OSPF neighbor relationship on the 10.0.123.0/24 network segment, and analyze why this is the case? And whether the results are the same when everyone is doing this experiment?
We first check the DR and BDR elections in the OSPF neighbor relationship on the 10.0.123.0/24 network segment. From the output below, we can know that the interface IP of the DR on this network segment is 10.0.123.1, and the interface IP of the BDR is 10.0.123.2.
[R1]display ospf peer
OSPF Process 1 with Router ID 10.0.1.1
Neighbors
Area 0.0.0.0 interface 10.0.123.1(GigabitEthernet0/0/0)'s neighbors
Router ID: 10.0.2.2 Address: 10.0.123.2
State: Full Mode:Nbr is Master Priority: 1
DR: 10.0.123.1 BDR: 10 .0.123 .2 PERSON: 0
Dead timer due in 40 sec
Retrans timer interval: 5
Neighbor is up for 01:03:35
Authentication Sequence: [ 0 ]
Router ID: 10.0.3.3 Address: 10.0.123.3
State: Full Mode:Nbr is Master Priority: 1
DR: 10.0.123.1 BDR: 10.0.123.2 PERSON: 0
Dead timer due in 33 sec
Retrans timer interval: 5
Neighbor is up for 01:02:27
Authentication Sequence: [ 0 ]
It is possible that the output of the experimental results of each person is different. Because in OSPF, the election of DR is not preemptive, that is, when there is a DR or BDR in the network, a new router entering the network cannot preempt the role of DR or BDR. In this network, the router that starts the OSPF process or accesses the network first becomes the DR on the network segment, and other routers become the BDR or DROther.
When DR fails, BDR will take over the position of DR. In the experiment, we can observe the change of DR role by resetting the OSPF process. Here, we reset the OSPF process of R1.
<R1>reset ospf process
Warning: The OSPF process will be reset. Continue? [Y/N]:y
[R1]display ospf peer
OSPF Process 1 with Router ID 10.0.1.1
Neighbors
Area 0.0.0.0 interface 10.0.123.1(GigabitEthernet0/0/0)'s neighbors
Router ID: 10.0.2.2 Address: 10.0.123.2
State: Full Mode:Nbr is Master Priority: 1
DR: 10.0.123.2 BDR: 10.0.123.3 PERSON: 0
Dead timer due in 34 sec
Retrans timer interval: 0
Neighbor is up for 00:00:19
Authentication Sequence: [ 0 ]
Router ID: 10.0.3.3 Address: 10.0.123.3
State: Full Mode:Nbr is Master Priority: 1
DR: 10.0.123.2 BDR: 10.0.123.3 PERSON: 0
Dead timer due in 39 sec
Retrans timer interval: 5
Neighbor is up for 00:00:19
Authentication Sequence: [ 0 ]
After resetting the OSPF process of R1, the original BDR 10.0.123.2 on the network becomes the new DR, and the original DROother 10.0.123.3 becomes the new BDR.
Next, we shut down the G0/0/0 interfaces of R1, R2, and R3, and use the command debugging ospf 1 event to check the specific process of OSPF adjacency establishment. Then try to open the G0/0/0 interfaces of R1, R2 and R3 at the same time. Observe the change process of the neighbor state and the process of DR and BDR election on the broadcast multi-access network.
<R1>debugging ospf 1 event
<R1>terminal debugging
[R1]interface GigabitEthernet 0/0/0
[R1-GigabitEthernet0/0/0]shut
[R1-GigabitEthernet0/0/0]undo shut
<R2>debugging ospf 1 event
<R2>terminal debugging
[R2]interface GigabitEthernet 0/0/0
[R2-GigabitEthernet0/0/0]shut
[R2-GigabitEthernet0/0/0]undo shut
<R3>debugging ospf 1 event
<R3>terminal debugging
[R3]interface GigabitEthernet 0/0/0
[R3-GigabitEthernet0/0/0]shutdown
[R3-GigabitEthernet0/0/0]undo shutdown
Perform the same operation on R2 and R3, and check the debug information of R3. Since the default interface priority of all routers is 1, the Router ID of the router will be referred to during the DR election. Among the three routers, the Router ID of R3 is the largest, so R3 becomes the DR on this network segment.
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:54:59.220.1+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802c Line: 1326 Level: 0x20
OSPF 1: Intf 10.0.123.3 Rcv InterfaceUp State Down -> Waiting.
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:54:59.230.1+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802c Line: 1440 Level: 0x20
OSPF 1 Send Hello Interface Up on 10.0.123.3
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:08.550.2+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802d Line: 1200 Level: 0x20
OSPF 1: Nbr 10.0.123.1 Rcv HelloReceived State Down -> Init.
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:09.530.2+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802d Line: 1200 Level: 0x20
OSPF 1: Nbr 10.0.123.2 Rcv HelloReceived State Down -> Init.
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:18.540.2+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802d Line: 1796 Level: 0x20
OSPF 1: Nbr 10.0.123.1 Rcv 2WayReceived State Init -> 2Way.
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:19.570.2+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802d Line: 1796 Level: 0x20
OSPF 1: Nbr 10.0.123.2 Rcv 2WayReceived State Init -> 2Way.
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:39.370.1+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802d Line: 1796 Level: 0x20
OSPF 1: Nbr 10.0.123.1 Rcv AdjOk? State 2Way -> ExStart.
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:39.370.2+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802d Line: 1796 Level: 0x20
OSPF 1: Nbr 10.0.123.2 Rcv AdjOk? State 2Way -> ExStart.
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:39.370.3+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802c Line: 2127 Level: 0x20
OSPF 1 Send Hello Interface State Changed on 10.0.123.3
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:39.370.4+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802c Line: 2138 Level: 0x20
OSPF 1: Intf 10.0.123.3 Rcv WaitTimer State Waiting -> DR.
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:39.390.1+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802d Line: 1909 Level: 0x20
OSPF 1: Nbr 10.0.123.1 Rcv NegotiationDone State ExStart -> Exchange.
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:39.390.2+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802d Line: 1909 Level: 0x20
OSPF 1: Nbr 10.0.123.2 Rcv NegotiationDone State ExStart -> Exchange.
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:39.400.1+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802d Line: 2021 Level: 0x20
OSPF 1: Nbr 10.0.123.1 Rcv ExchangeDone State Exchange -> Loading.
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:39.400.2+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802d Line: 2423 Level: 0x20
OSPF 1: Nbr 10.0.123.1 Rcv LoadingDone State Loading -> Full.
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:39.400.3+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802d Line: 2021 Level: 0x20
OSPF 1: Nbr 10.0.123.2 Rcv ExchangeDone State Exchange -> Loading.
[R3-GigabitEthernet0/0/0]
Oct 12 2016 11:55:39.400.4+00:00 R3 RM/6/RMDEBUG:
FileID: 0xd017802d Line: 2423 Level: 0x20
OSPF 1: Nbr 10.0.123.2 Rcv LoadingDone State Loading -> Full.
<R1>undo debugging all
<R2>undo debugging all
<R3>undo debugging all
When the interface is just opened, the interface status changes from Down to Waiting. At this time, the router starts to exchange Hello data packets. After waiting for about 40 seconds, the interface of R3 changes from Waiting to DR.
Step 4. Configure the network type of the Loopback interface in OSPF
Observe the routing table of R1, focusing on these two routes: 10.0.2.2/32 and 10.0.3.3/32.
[R1]display ip routing-table
Route Flags: R - relay, D - download to fib
----------------------------------------------------------------------------
Routing Tables: Public
Destinations : 12 Routes : 12
Destination/Mask Proto Pre Cost Flags NextHop Interface
10.0.1.0/24 Direct 0 0 D 10.0.1.1 LoopBack0
10.0.1.1/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.1.255/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.2.2/32 OSPF 10 1 D 10.0.123.2 GigabitEthernet0/0/0
10.0.3.3/32 OSPF 10 1 D 10.0.123.3 GigabitEthernet0/0/0
10.0.123.0/24 Direct 0 0 D 10.0.123.1 GigabitEthernet0/0/0
10.0.123.1/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
10.0.123.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
127.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
255.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
When configuring the loopback interface addresses of R2 and R3, the mask used is 24 bits. Why is the route with a 32-bit mask displayed in the routing table here?
Run the display ospf interface LoopBack 0 verbose command to check the status of OSPF running on the Loopback 0 interface.
[R1]display ospf interface LoopBack 0 verbose
OSPF Process 1 with Router ID 10.0.1.1
Interfaces
Interface: 10.0.1.1 (LoopBack0)
Cost: 0 State: P-2-P Type: P2P MTU: 1500
Timers: Hello 10 , Dead 40 , Poll 120 , Retransmit 5 , Transmit Delay 1
IO Statistics
Type Input Output
Hello 0 0
DB Description 0 0
Link-State Req 0 0
Link-State Update 0 0
Link-State Ack 0 0
ALLSPF GROUP
OpaqueId: 0 PrevState: Down
It can be seen that for the loopback interface, OSPF knows that the network segment can only have one IP address, so the subnet mask of the advertised route is 32 bits.
Change the network type of the Loopback0 interface on R2 to Broadcast. When OSPF advertises the network information of this interface, it will use a 24-bit mask to advertise.
[R2]interface LoopBack 0
[R2-LoopBack0]ospf network-type broadcast
At this time, we see that the routing subnet mask of the Loopback 0 address advertised by R2 is 24 bits.
[R1]display ip routing-table
Route Flags: R - relay, D - download to fib
----------------------------------------------------------------------------
Routing Tables: Public
Destinations : 12 Routes : 12
Destination/Mask Proto Pre Cost Flags NextHop Interface
10.0.1.0/24 Direct 0 0 D 10.0.1.1 LoopBack0
10.0.1.1/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.1.255/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.2.2/24 OSPF 10 1 D 10.0.123.2 GigabitEthernet0/0/0
10.0.3.3/32 OSPF 10 1 D 10.0.123.3 GigabitEthernet0/0/0
10.0.123.0/24 Direct 0 0 D 10.0.123.1 GigabitEthernet0/0/0
10.0.123.1/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
10.0.123.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
127.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
255.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
Run the display ospf interface LoopBack 0 verbose command to check the running status of the Loopback interface. You can see that the network type of the interface is Broadcast.
[R2]display ospf interface LoopBack 0 verbose
OSPF Process 1 with Router ID 10.0.2.2
Interfaces
Interface: 10.0.2.2 (LoopBack0)
Cost: 0 State: DR Type: Broadcast MTU: 1500
Priority: 1
Designated Router: 10.0.2.2
Backup Designated Router: 0.0.0.0
Timers: Hello 10 , Dead 40 , Poll 120 , Retransmit 5 , Transmit Delay 1
IO Statistics
Type Input Output
Hello 0 0
DB Description 0 0
Link-State Req 0 0
Link-State Update 0 0
Link-State Ack 0 0
ALLSPF GROUP
ALLDR GROUP
OpaqueId: 0 PrevState: Waiting
Step 5. Modify the OSPF cost value of the interface
First check the cost value of the route from R1 to the Loopback0 interface of R3 on R1. We can see that the cost value of the route to 10.0.3.3/32 is 1.
[R1]display ip routing-table
Route Flags: R - relay, D - download to fib
----------------------------------------------------------------------------
Routing Tables: Public
Destinations : 12 Routes : 12
Destination/Mask Proto Pre Cost Flags NextHop Interface
10.0.1.0/24 Direct 0 0 D 10.0.1.1 LoopBack0
10.0.1.1/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.1.255/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.2.2/24 OSPF 10 1 D 10.0.123.2 GigabitEthernet0/0/0
10.0.3.3/32 OSPF 10 1 D 10.0.123.3 GigabitEthernet0/0/0
10.0.123.0/24 Direct 0 0 D 10.0.123.1 GigabitEthernet0/0/0
10.0.123.1/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
10.0.123.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
127.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
255.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
Change the cost of the G0/0/0 interface on R1 to 20, and modify the cost of the G0/0/0 interface on R3 to 10.
[R1]interface GigabitEthernet 0/0/0
[R1-GigabitEthernet0/0/0]ospf cost 20
[R1-GigabitEthernet0/0/0]quit
[R3]interface GigabitEthernet 0/0/0
[R3-GigabitEthernet0/0/0]ospf cost 10
[R3-GigabitEthernet0/0/0]quit
Check the cost value of the route from R1 to the Loopback0 interface of R3 again, and you can see that the cost value of the route to 10.0.3.3/32 is 20.
[R1]display ip routing-table
Route Flags: R - relay, D - download to fib
----------------------------------------------------------------------------
Routing Tables: Public
Destinations : 12 Routes : 12
Destination/Mask Proto Pre Cost Flags NextHop Interface
10.0.1.0/24 Direct 0 0 D 10.0.1.1 LoopBack0
10.0.1.1/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.1.255/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.2.2/24 OSPF 10 20 D 10.0.123.2 GigabitEthernet0/0/0
10.0.3.3/32 OSPF 10 20 D 10.0.123.3 GigabitEthernet0/0/0
10.0.123.0/24 Direct 0 0 D 10.0.123.1 GigabitEthernet0/0/0
10.0.123.1/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
10.0.123.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
127.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
255.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
Looking at the cost value of 10.0.1.1/32 on R3, you can see that the value is 10.
[R3]display ip routing-table
Route Flags: R - relay, D - download to fib
----------------------------------------------------------------------------
Routing Tables: Public
Destinations : 12 Routes : 12
Destination/Mask Proto Pre Cost Flags NextHop Interface
10.0.1.1/32 OSPF 10 10 D 10.0.123.1 GigabitEthernet0/0/0
10.0.2.0/24 OSPF 10 10 D 10.0.123.2 GigabitEthernet0/0/0
10.0.3.0/24 Direct 0 0 D 10.0.3.3 LoopBack0
10.0.3.3/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.3.255/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.123.0/24 Direct 0 0 D 10.0.123.3 GigabitEthernet0/0/0
10.0.123.3/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
10.0.123.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
127.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
255.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
Step 6. Configure OSPF Silent-interface
Configure the G0/0/0 interface of R1 as a silent-interface.
[R1]ospf 1
[R1-ospf-1]silent-interface GigabitEthernet 0/0/0
[R1-ospf-1]quit
Check the neighbor relationship establishment and routing table learning status of R1. It can be found that the routing entries learned from OSPF in the routing table disappear.
[R1]display ip routing-table
Route Flags: R - relay, D - download to fib
----------------------------------------------------------------------------
Routing Tables: Public
Destinations : 12 Routes : 12
Destination/Mask Proto Pre Cost Flags NextHop Interface
10.0.1.0/24 Direct 0 0 D 10.0.1.1 LoopBack0
10.0.1.1/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.1.255/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.123.0/24 Direct 0 0 D 10.0.123.1 GigabitEthernet0/0/0
10.0.123.1/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
10.0.123.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
127.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
255.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
View the neighbor list of R1, and you can see that the neighbor relationship between R1, R2, and R3 also disappears. After an interface is set as a Silent-interface in RIP, the interface will no longer send RIP updates. However, in OSPF, routers need to establish neighbor relationships before exchanging routing information. When an interface is set as Silent-interface, the interface will no longer receive or send Hello packets. As a result, the interface cannot form neighbor relationships with other routers.
[R1]display ospf interface GigabitEthernet 0/0/0
OSPF Process 1 with Router ID 10.0.1.1
Interfaces
Interface: 10.0.123.1 (GigabitEthernet0/0/0)
Cost: 20 State: DR Type: Broadcast MTU: 1500
Priority: 1
Designated Router: 10.0.123.1
Backup Designated Router: 0.0.0.0
Timers: Hello 10 , Dead 40 , Poll 120 , Retransmit 5 , Transmit Delay 1
Silent interface, No hellos
Restore the G0/0/0 interface of R1 to the default state, and configure the Loopback0 interface of the three routers as Silent-interface.
[R1]ospf 1
[R1-ospf-1]undo silent-interface GigabitEthernet0/0/0
[R1-ospf-1]silent-interface LoopBack 0
[R1-ospf-1]quit
[R2]ospf 1
[R2-ospf-1]silent-interface LoopBack 0
[R1-ospf-1]quit
[R3]ospf 1
[R3-ospf-1]silent-interface LoopBack 0
[R1-ospf-1]quit
Check the routing table of R1. It can be seen that setting the loopback to Silent-interface does not affect the advertisement of the interface route.
[R1]display ip routing-table
Route Flags: R - relay, D - download to fib
----------------------------------------------------------------------------
Routing Tables: Public
Destinations : 12 Routes : 12
Destination/Mask Proto Pre Cost Flags NextHop Interface
10.0.1.0/24 Direct 0 0 D 10.0.1.1 LoopBack0
10.0.1.1/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.1.255/32 Direct 0 0 D 127.0.0.1 LoopBack0
10.0.2.0/24 OSPF 10 20 D 10.0.123.2 GigabitEthernet0/0/0
10.0.3.3/32 OSPF 10 20 D 10.0.123.3 GigabitEthernet0/0/0
10.0.123.0/24 Direct 0 0 D 10.0.123.1 GigabitEthernet0/0/0
10.0.123.1/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
10.0.123.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet0/0/0
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
127.255.255.255/32Direct 0 0 D 127.0.0.1 InLoopBack0
Additional Experiments : Think and Verify
Why is the wildcard mask 0.0.0.0 used when configuring OSPF, and the wildcard mask 0.0.0.255 can also be used in the actual configuration? Think about the difference between these two expressions?
Analyze which types of interfaces should be configured as silent-interfaces in the actual network?
final device configuration
<R1>display current-configuration
[V200R007C00SPC600]
#
sysname R1
#
interface GigabitEthernet0/0/0
ip address 10.0.123.1 255.255.255.0
ospf cost 20
#
interface LoopBack0
ip address 10.0.1.1 255.255.255.0
#
ospf 1 router-id 10.0.1.1
silent-interface LoopBack0
area 0.0.0.0
authentication-mode simple plain huawei
network 10.0.1.1 0.0.0.0
network 10.0.123.1 0.0.0.0
#
return
<R2>display current-configuration
[V200R007C00SPC600]
#
sysname R2
#
interface GigabitEthernet0/0/0
ip address 10.0.123.2 255.255.255.0
#
interface LoopBack0
ip address 10.0.2.2 255.255.255.0
ospf network-type broadcast
#
ospf 1 router-id 10.0.2.2
silent-interface LoopBack0
area 0.0.0.0
authentication-mode simple plain huawei
network 10.0.2.2 0.0.0.0
network 10.0.123.2 0.0.0.0
#
return
<R3>display current-configuration
[V200R007C00SPC600]
#
sysname R3
#
interface GigabitEthernet0/0/0
ip address 10.0.123.3 255.255.255.0
ospf cost 10
#
interface LoopBack0
ip address 10.0.3.3 255.255.255.0
#
ospf 1 router-id 10.0.3.3
silent-interface LoopBack0
area 0.0.0.0
authentication-mode simple plain huawei
network 10.0.3.3 0.0.0.0
network 10.0.123.3 0.0.0.0
#
return