Network design - Master Tran Van Long, Master Tran Dinh Tung Compiled

Area ID (4 octets): Identification of the area to which the packet belongs. Checksum (2 octets): Checks the packet for errors.

Authentication type (2 octets): Contains the authentication type. All information exchanged in OSPF must be authenticated. There are 3 types of authentication:

Type 0 (Null): Not authenticated.

Type 1 (Plain text): Authentication using plain text. Type 2 (MD5): Authentication using MD5 encryption.

Authentication data (8 octets): Contains authentication information. Data: Contains OSPF packet data.

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4) OSPF configuration command

Router#config t

Router(config)#router ospf [process_ID] //process_ID is the index that identifies the routing process on the Router, its value ranges from 1 to 65535.

Router(config-router)#network [Network_ID] [wildcard_mark] area [area_ID]// Add the IP addresses of the networks that are directly connected to the Router. These networks are conventionally located in an area called area_ID (0 - 4294967295). For example: (config - router)

#network 175.14.0.0 0.0.255.255 area 0

5) Application examples

Given the network diagram with the same IP address as shown below. Configure OSPF routing protocol on 3 Routers so that the Routers can Ping each other.

Figure 4.41. OSPF routing protocol configuration network diagram Interface configuration:

Router 1:

Router(config)#hostname R1 R1(config)#int s2/0

R1(config-if)#ip address 172.16.10.1 255.255.0.0 R1(config-if)#no shutdown

R1(config-if)#clock rate 64000 R1(config-if)#exit

R1(config)# R1(config)#int fa0/0

R1(config-if)#ip address 10.1.1.1 255.255.255.0 R1(config-if)#no shutdown

R1(config-if)#exit R1(config)#

Router 2:

Router(config)#hostname R2 R2(config)#int fa0/0

R2(config-if)#ip address 10.1.1.2 255.255.255.0 R2(config-if)#no shutdown

R2(config-if)#exit R2(config)#

Router 4:

Router(config)#hostname R4 R4(config)#int s2/0

R4(config-if)#ip address 172.16.10.2 255.255.0.0 R4(config-if)#no shutdown

R4(config-if)#clock rate 64000 R4(config-if)#exit

R4(config)#

Configure OSPF routing protocol: Router 1:

R1#config t

R1(config)#router ospf 100 (100 is Process_ID)

Figure 4.42. Process ID declaration

Add the IP addresses of the networks that are directly connected to R1:

Router 2:

Similar to Router 1

Figure 4.43. Add network IP addresses

Router 4:

Similar to Router 1

Figure 4.44. Add network IP addresses

Figure 4.45. Add network IP addresses

Check the results:

From Router 2 Ping to port Se2/0 of Router 4 with IP address 172.16.10.2

Figure 4.46. Ping command results

From Router 4 Ping to port Fa0/0 of Router 2 with IP address 10.1.1.2

Figure 4.47. Ping command results Thus, all Routers have been able to Ping each other.

View Router 2's routing table

Figure 4.48. Router 2's routing table View Router 1's routing protocol information

Figure 4.49. Routing protocol information Displaying the OSPF database contents of Router 1

Figure 4.50. OSPF database contents

4.8.5. EIGRP routing protocol

1) Introduction

EIGRP (Enhanced Interior Gateway Routing Protocol) is a Cisco proprietary routing protocol developed from IGRP (Interior Gateway Routing Protocol, a link-state routing protocol). Unlike IGRP, which is a classful routing protocol, EIGRP supports classless inter-domain routing (CIDR) and allows network designers to optimize address space using VLSM (Variable Length Subnet Mask). Compared to IGRP, EIGRP has faster convergence time, better scalability, and higher loop tolerance.

Furthermore, EIGRP can also replace Novell RIP (Novell Routing Information Protocol) and RTMP (Apple Talk Routing Table Maintenance Protocol) to efficiently serve both IPX and Apple Talk networks.

EIGRP is considered a hybrid protocol because it combines the advantages of both distance vector and link state routing protocols. EIGRP is chosen for large, multiprotocol networks built on Cisco Routers.

2) Characteristics

a) Routers store information about routes and network topology in RAM, so they respond quickly to changes in network topology. EIGRP stores the routes it learns in a special way, each with its own state and markings to provide additional useful information. Like OSPF, EIGRP also stores this information in different tables and databases. EIGRP has three types of tables:

Neighbor table

Topology table Routing table

- Neighbor table:

The most important table in EIGRP. Each EIGRP Router maintains a neighbor table, which is a list of routers adjacent to it. This table is similar to the OSPF neighbor database.

- Network structure table:

The topology table is the table that provides data to build the EIGRP routing table. DUAL takes information from the neighbor table and the topology table to calculate the lowest-cost path to each destination network.

Each EIGRP Router maintains a separate topology table corresponding to each different type of network protocol. The topology table contains information about all paths

that the Router learns. Thanks to this information, the Router can determine an alternative path quickly when necessary. The DUAL algorithm chooses the best path to the destination network called the Successor.

The following is the information contained in the network topology table:

Feasible distance (FD): The FD of the Router under consideration is the distance (metric) from it to the destination network.

Advertised distance (AD): The AD of the Router under consideration is the distance (metric) from its neighboring Router to the destination network.

Route source: The source of information about a particular route. This information is only available for routes learned from outside the EIGRP network.

Reported disdiance: Routing parameters to a neighboring Router. Information about the interface the Router uses to reach the destination network.

Path state: The passive state (P) is a stable state, ready for use. The active state (A) is a state in the process of DUAL's recalculation.

Figure 4.51. Network structure table

The topology table also stores a lot of other information about routes. EIGRP classifies routes into areas and outside areas. Area routes are routes originating from within the EIGRP autonomous system (AS), EIGRP has a label (Administrator tag) with a value from 0 to 255 to distinguish which type of route it belongs to. Outside areas routes are routes originating from outside the EIGRP AS, outside areas routes are routes learned from other routing protocols such as RIP, OSPF and IGRP.

Figure 4.52. Administrator tag value label

- Route selection table:

The EIGRP routing table maintains a list of best paths to destination networks. The information in the routing table is generated from the topology table and the neighbor table.

The path chosen as the primary path to the destination network is called the Successor. From the information in the neighbor table and the network topology table, DUAL chooses a primary path. There can be up to 4 Successors to a destination network. These paths have equal or unequal costs. Information about Successors is also placed in the network topology table.

Figure 4.53. Successor Line

Figure 4.54. Neighbor table and network topology table

Figure 4.55. Using the DUAL algorithm

Network design - Master Tran Van Long, Master Tran Dinh Tung Compiled - 16

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