The Router Eigrp [As Number] Cisco command

The Cisco command 'router eigrp [AS_number]' is used to enable Enhanced Interior Gateway Routing Protocol (EIGRP) routing on a Cisco router and assign an autonomous system (AS) number to it. Here's a more detailed explanation:

Command Syntax:

router eigrp [AS_number]

Purpose:

• Enables EIGRP routing on the router.
• Assigns an AS number to the router for routing.

Usage:

1. Enter the 'configure terminal' command to enter global configuration mode.
2. Use the 'router eigrp [AS_number]' command to enable EIGRP and assign an AS number.
3. Configure additional EIGRP parameters as needed, such as network statements, redistributive routes, etc.
4. Use the 'end' command to exit configuration mode and save your changes.

Type of Equipment:

• Cisco routers that support EIGRP

Command Details:

• '[AS_number]': This is the AS number to be assigned to the router. It must be a unique number within the EIGRP routing domain.
• You can configure multiple EIGRP instances on a single router by assigning different AS numbers to each instance.
• EIGRP is a distance-vector routing protocol that uses the Diffusing Update Algorithm (DUAL) to calculate the best paths to destinations.
• EIGRP supports various features such as route summarization, load balancing, and fast convergence.

Additional Information:

• EIGRP is commonly used in enterprise networks and service provider networks.
• It is also widely used in large-scale networks with complex routing requirements.
• EIGRP can be used together with other routing protocols, such as OSPF, BGP, or RIP, to create a comprehensive routing solution.
• The 'router eigrp [AS_number]' command is equivalent to the 'eigrp router [AS_number]' command in Cisco IOS.

router eigrp [AS_number] Usage Examples

1. Enabling EIGRP on a Router:

Command: router eigrp 10

Explanation: This command enables EIGRP on a router and assigns it to autonomous system 10. The value "10" can be replaced with any valid AS number.

2. Configuring EIGRP Network Parameters:

Command: router eigrp 10 network 192.168.1.0 0.0.0.255

Explanation: This command configures the network parameters for EIGRP in autonomous system 10. It specifies the network address "192.168.1.0" and the subnet mask "0.0.0.255."

3. Redistributing Connected Routes into EIGRP:

Command: redistribute connected metric 100 1000 255 1 1

Explanation: This command redistributes routes learned from directly connected networks into EIGRP. The "metric 100 1000 255 1 1" specifies the default metric attributes for the redistributed routes.

4. Summarizing Routes in EIGRP:

Command: ip summary-address eigrp 10 192.168.0.0/16

Explanation: This command summarizes the routes matching "192.168.0.0/16" in EIGRP autonomous system 10. The summarized route will be advertised with a shorter prefix.

5. Configuring EIGRP Stub Routes:

Command: eigrp stub

Explanation: This command configures the router to be an EIGRP stub router. Stub routers only accept routes from their upstream neighbors and do not advertise their routes further.

6. Configuring EIGRP Default Routes:

Command: default-information originate 192.168.0.0/24

Explanation: This command originates a default route "192.168.0.0/24" via EIGRP. The default route will be advertised to all EIGRP neighbors.

7. Configuring EIGRP Route Maps:

Command: route-map RM-1 match ip address 192.168.1.0/24

Explanation: This command creates an EIGRP route map named "RM-1" and matches packets with an IP address "192.168.1.0/24." Route maps are used to control the advertisement and acceptance of routes.

8. Applying EIGRP Route Maps:

Command: router eigrp 10 distribute-list RM-1 out

Explanation: This command applies the route map "RM-1" to outgoing EIGRP updates in autonomous system 10. This allows the router to filter routes before they are advertised to neighbors.