Cisco EIGRP Configuration: A Quick How To

Cisco’s Enhanced Interior Gateway Routing Protocol (EIGRP) is a proprietary routing protocol developed by Cisco Systems. EIGRP falls into the category of advanced distance-vector routing protocols, although it incorporates features that make it more like a hybrid protocol. EIGRP is designed to efficiently handle routing within an autonomous system (AS) and is commonly used in enterprise networks.

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Key features of Cisco EIGRP include:

1. Fast Convergence: EIGRP is known for its fast convergence capabilities. It uses Diffusing Update Algorithm (DUAL) to quickly converge the network topology when there are topology changes, such as link failures or network additions.
2. Advanced Metrics: EIGRP uses a composite metric to determine the best path for routing. This metric takes into account bandwidth, delay, reliability, and load. This allows EIGRP to make intelligent routing decisions based on a variety of factors.
3. VLSM and CIDR Support: EIGRP supports Variable Length Subnet Masking (VLSM) and Classless Inter-Domain Routing (CIDR), enabling efficient use of IP address space and allowing for more flexible network design.
4. Route Summarization: EIGRP can perform route summarization, reducing the number of routes advertised and helping to optimize routing table size.
5. Neighbor Relationships: EIGRP forms neighbor relationships with directly connected routers. These relationships enable efficient exchange of routing information.
6. Dual Stacking: EIGRP supports both IPv4 and IPv6 routing, allowing for smooth transition to IPv6 networks.
7. Loop-Free Routing: EIGRP ensures loop-free routing by using the Diffusing Update Algorithm. This algorithm guarantees that there will be no routing loops in the network.
8. Unequal-Cost Load Balancing: EIGRP supports unequal-cost load balancing, allowing traffic to be distributed across multiple paths with different metrics.
9. Route Authentication: EIGRP supports route authentication, adding an extra layer of security to routing updates.

EIGRP operates within a single autonomous system and is not designed to be used as an inter-domain routing protocol like BGP. It’s commonly used in enterprise networks due to its efficient convergence, scalability, and support for various IP features.

However, it’s important to note that EIGRP is a Cisco-proprietary protocol, which means it generally only works on Cisco routers and devices. If you’re working in a multi-vendor environment, you might need to consider using standard protocols like OSPF or BGP for interoperability.

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Cisco EIGRP Configuration

Configuring Cisco’s Enhanced Interior Gateway Routing Protocol (EIGRP) involves a series of steps that need to be executed on the Cisco router. EIGRP is a Cisco-proprietary routing protocol used for routing within an autonomous system (AS). Here’s a basic outline of the steps required to configure EIGRP on a Cisco router:

Enable EIGRP and Define an Autonomous System (AS):

router eigrp <AS_number>

Replace <AS_number> with the autonomous system number you want to use. This number helps differentiate EIGRP instances from each other.

Define Networks to Advertise: Specify the networks you want EIGRP to advertise. This is done using the network command followed by the network address and wildcard mask.

network <network_address> <wildcard_mask>

Replace <network_address> with the network you want to advertise and <wildcard_mask> with the wildcard mask that corresponds to that network.

Optional: Adjust Metrics and Other Parameters: You can adjust various EIGRP parameters, such as bandwidth, delay, reliability, and load. These parameters affect the metric calculation.

metric weights 0 1 0 1 0 0

The above command sets bandwidth and delay as the only non-default metric components.

Optional: Filter Routes: You can use distribute-lists or access-lists to filter which routes are advertised or learned. For example, you might use distribute-list to filter routes based on specific criteria.

distribute-list <access-list-name> <strong>out</strong> <<strong>interface</strong>>

View EIGRP Status and Neighbors: To view EIGRP status and neighbor information, use the following commands:

<strong>show</strong> ip eigrp neighbors
<strong>show</strong> ip eigrp topology

Save Configuration Changes: After configuring EIGRP, remember to save your configuration changes to ensure they persist after a router restart.

copy running-config startup-config

Keep in mind that this is just a basic outline of the configuration process. The specific commands you use might vary based on your network’s requirements and the Cisco IOS version you’re using. Always refer to the official Cisco documentation or relevant resources for the most accurate and up-to-date information. Additionally, the network topology, IP addressing scheme, and other factors will influence the exact configuration you need to implement.

Frequently Asked Questions About Cisco EIGRP