CCNP EIGRP Components

EIGRP Tables
DUAL uses the EIGRP tables, which are provided. Within the EIGRP tables you will find a neighbor table, a topology table and a routing table.

Here are functions each table performs.
Neighbours Table - shows all neighbours adjacent to router
Topology Table - shows all route entries learned by the router
Routing Table – shows the best route to get to other points on the network


EIGRP Packets

Uses Five Packet Types

Hello
Check if the neighbor is up
Update
Used to send routing updates
Query
Finds out information from neighbors regarding routing updates
Reply
This is where the neighbors give a response
Acknowledgement
If you send a message, it must be acknowledged by the person who receives it. This packet is used to acknowledge a reliable packet.
The above are five main packets EIGRP uses. However, EIGRP can also use a packet called request.

Request – This packet is used to get information for a specific route. The information is received from one or more neighbors. Therefore the methods to send a request can either be through a unicast or a multicast process.




EIGRP Metric
EIGRP uses the metric component.
Metric is a Calculation done by the Routing protocol to determine the best path through a network. Since EIGRP uses 32 bits for its calculation it is metric is multiplied by 256. Metric consists of 5 components which are bandwidth, delay, reliability, loading, MTU.

EIGRP Metric Calculation
Metric = bandwidth + delay

EIGRP uses two of the components of metric which are bandwidth and delay. In the bandwidth, the measurement is based on the smallest amount of consumed data between the source and destination. In delay the delays in the path is measured.

CCNP EIGRP Fundamentals

Enhanced Interior Gateway Routing Protocol (EIGRP) is an advanced distance vector protocol. However, it also has a hybrid routing protocol capability since it combines the best of a distance vector protocol with link state algorithms by using partial updates and neighbor discovery. From other distance vector protocols it offers improvements such as reduction of bandwidth use, fast convergence, support for classless subnets which use CIDR and VLSM, and support for multiple routed protocols like Apple Talk, IP and IPX.


Among the key feature of EIGRP the following are included:
1)Fast Convergence
2)VLSM Subnetting
3)Partial Update
4)Multiple Network Layer Protocol Support

Fast Convergence: EIGRP stores its neighbours routing table so it can take alternatives routes if it original route is gone. Also, it has the ability to ask its neighbours for alternative routes if needed.

VLSM Support: EIGRP uses classless subnets within it routing network. For classful major networks it automatically summarizes routes on the attached interfaces. EIGRP also support manual summarization, and for this it uses VLSM to force a summary route from an interface.

Partial Updates: Partial Updates contain information about the change routes, and they are sent when route need a change in its metric or path. They are handled by multicast or unicast packet instead of broadcast packets since it reduces the use of bandwidth.

Multiple Network Layer Protocol: EIGRP can support IP, IPX, and AppleTalk routed protocols which enable EIGRP to have good stability and high performance networks.


EIGRP has four unique key components.

1. Protocol-dependent modules: Responsible for requirements within the network layer protocols.
2. Reliable Transport Protocol (RTP) : Support Unicast and Multicast transmission. RTP's main role is to guarantee a a timely, reliable and efficiently. EIGRP reliable transport protocol (RTP) guarantees timely, reliable, and efficient exchange of routing data between EIGRP neighbours.
3. Neighbor Discovery and Recovery: Discovery and Recovery allow routers about the other routers that are attached on the network neighbor discovery and recovery enables routers to dynamically learn about other routers on their directly attached network . It does this by allowing EIGRP to build a neighbor table which shows all neighbors adjacent to the router, to a topology table which discovers routes and routing table which choses the best path.
   

4. Diffusing Update Algorithm (DUAL): DUAL is the heart of EIGRP. It relies on
protocols and data structures to provide all the routers in a network to lead up to the final route.

EIGRP Tables

Neighbours Table - shows all neighbours adjacent to router

Topology Table - shows all route entries learned by the router

Routing Table – shows the best route to get to other points on the network

OSPF Tables

Neighbours Table - shows all neighbours adjacent to router.

Topology Table - shows all route entries learned by the router.

Routing Table – shows the best route to get to other points on the network.

Routing Table

A routing table contains the information necessary to forward a packet along the best path toward its destination. Each packet contains information about its origin and destination. When a packet is received, a network device examines the packet and matches it to the routing table entry providing the best match for its destination. The table then provides the device with instructions for sending the packet to the next hop on its route across the network.

A basic routing table includes the following information:

Destination: The IP address of the packet's final destination
Next hop: The IP address to which the packet is forwarded
Interface: The outgoing network interface the device should use when forwarding the packet to the next hop or final destination

Metric: Assigns a cost to each available route so that the most cost-effective path can be chosen

Routes: Includes directly-attached subnets, indirect subnets that are not attached to the device but can be accessed through one or more hops, and default routes to use for certain types of traffic or when information is lacking.