Result Analysis of router OSPF Configuration

Route table query on the R1 Router

It is particularly important to view the route table, because after the entire OSPF protocol is successfully run on three devices, the table items of the route tables of the three devices should be the same, the route entries and content in the route table are the focus of viewing the route table. Therefore, you must learn to analyze and identify the route table.

Enter the query command in the privileged mode of R1. Three R routes are displayed.

 
 

  
  
R1 # sh ip route query the R1 route table
  
  
 
  
  
Codes: C-connected, S-static, I-IGRP, R-RIP, M-mobile, B-BGP
  
  
 
  
  
D-OSPF, EX-VPN 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, su-IS summary, L1-IS-level-1, L2-IS level-2
  
  
 
  
  
Ia-IS inter area, *-candidate default, U-per-user static route
  
  
 
  
  
O-ODR, P-periodic downloaded static route
  
  
 
  
  
Gateway of last resort is not set
  
  
 
  
  
1.0.0.0/24 is subnetted, 1 subnets
  
  
 
  
  
C 1.1.1.0 is directly connected, Loopback0
  
  
 
  
  
2.0.0.0/32 is subnetted, 1 subnets
  
  
 
  
  
O 2.2.2.2 [110/65] via 199.99.1.2, 00:04:14, Serial1/0
  
  
 
  
  
3.0.0.0/32 is subnetted, 1 subnets
  
  
 
  
  
O 3.3.3.3 [110/129] via 199.99.1.2, 00:04:14, Serial1/0
  
  
 
  
  
O 199.99.2.0/24 [110/128] via 199.99.1.2, 00:04:14, Serial1/0
  
  
 
  
  
C 199.99.1.0/24 is directly connected, Serial1/0
 
 

The above "C" route is a direct connection interface route, meaning: the route that grows on the router body, that is, the interface route, as long as the interface link is normal, the IP address is successfully configured, it automatically enters the route table to form a "C" route. The "O" routing represents the OSPF routing protocol, which will be further analyzed in the following sections.

OSPF configuration-Test Result Analysis

The analysis of the test results is very important. This result has exceeded the scope of the configuration results. It should be said that it is the analysis and troubleshooting of the Protocol process.

Route table Item Analysis

In the route table, what are the meanings of all table items and the understanding of each detail section. It is very important for every beginner. Through understanding this, we can lay a very solid theoretical foundation.

 
 

  
  
R1 # sh ip route query the R1 route table
  
  
 
  
  
Codes: C-connected, S-static, I-IGRP, R-RIP, M-mobile, B-BGP
  
  
 
  
  
D-OSPF, EX-VPN 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, su-IS summary, L1-IS-level-1, L2-IS level-2
  
  
 
  
  
Ia-IS inter area, *-candidate default, U-per-user static route
  
  
 
  
  
O-ODR, P-periodic downloaded static route
  
  
 
  
  
Gateway of last resort is not set
  
  
 
  
  
1.0.0.0/24 is subnetted, 1 subnets
  
  
 
  
  
C 1.1.1.0 is directly connected, Loopback0
  
  
 
  
  
2.0.0.0/32 is subnetted, 1 subnets
  
  
 
  
  
O 2.2.2.2 [110/65] via 199.99.1.2, 00:04:14, Serial1/0
  
  
 
  
  
3.0.0.0/32 is subnetted, 1 subnets
  
  
 
  
  
O 3.3.3.3 [110/129] via 199.99.1.2, 00:04:14, Serial1/0
  
  
 
  
  
O 199.99.2.0/24 [110/128] via 199.99.1.2, 00:04:14, Serial1/0
  
  
 
  
  
C 199.99.1.0/24 is directly connected, Serial1/0
 
 

The preceding command clearly shows the table items of the R1 route table. "C" indicates a direct connection route, that is, the physical interface advertised on the router is a local link; "O" indicates that the routing protocol is learned through OSPF; "2.2.2.2" indicates the learned routing prefix; "[110/65]" indicates that the OSPF protocol is managed at a distance of 110 and the COST overhead is 65; "00:04:14" indicates the time when route information is learned. This time is very important. When you are looking at Route status updates later, you need to observe the time when route entries are different from other times; "via 199.99.1.2" indicates the next hop address; "Serial1/0" indicates the interface learned from.

Analyze how COST overhead is calculated for 65. OSPF has a standard overhead setting. The overhead of the serial interface is 64, and the overhead of Ethernet 10 m is 10, M Ethernet overhead is 1 and logical interface overhead is 1. When we learn 2.2.2.2 of the loop0 interface of R2, the overhead of the serial interface from R1 to R2 is 64, the loo0 overhead of R2. The total overhead is 65.

The process of viewing the analysis results of the route table in the router OSPF configuration is complete. Please master the OSPF configuration of the router in conjunction with previous articles.

1. Basic description of router OSPF Configuration
2. Describes the basic interface configuration for router OSPF configuration.
3. Test interface connectivity for router OSPF Configuration
4. Describes how to query the OSPF neighbor table on a router in the OSPF configuration of a router.
5. Describes the basic configuration and connectivity test of OSPF in Router OSPF configuration.
6. Describes how to query the connection status database of ospf on a Router Based on the OSPF configuration of a router.