A full form of EIGRP is Enhanced Interior Gateway Routing Protocol. EIGRP is an advanced distance-vector & Hybrid Routing. It is not used distance for the best path but still hops count will be forwarded in EIGRP updates. Next hop calculates by a source of update (this feature of Distance vector routing protocol).
In EIGRP three tables made: Neighbor Table, Topology Table, Routing Table (this feature of Link State Routing Protocol).
EIGRP is a classless routing protocol. When a Router update of any network then it will send the same network ID or Subnet this way called classless. It is layer three routing Protocol: encapsulate with IP packets used 88 port no. AD (Administrative Distance) for the same domain or internal route used 90. AD (Administrative Distance) for the different domains or external routes used 170.
EIGRP works on AS (Autonomous System): which shares the same routing policies and its control by a single network Admin.
What Is EIGRP In Networking
Above is the properties of EIGRP, I Hope you know these all things and this will help you to shine your EIGRP memory. Now my concern is that EIGRP to make communication possible inside an AS & how EIGRP will form its neighbor???????
#Router EIGRP <1-65535> AS number range: This is the command for enabling EIGRP on a Router.
Note* on neighbor Router AS must be the same.
#Network 220.127.116.11: this is class A & network Bit 8. By this command all interface where the 8 Bit match & EIGRP network enables.
Wildcard Mask used for matching that which OCTET will Match for the network.
When EIGRP enable on an Interface:
- A router will start a dynamic neighbor discovery on that interface.
- The router will add a network present on that interface to the local topology table.
- A router will discover neighbors with hello messages uses multicast address 18.104.22.168.
When hello message sends then first match the parameter for the neighbor ship after that it will become a neighbor.
You also read that how to work DHCP Dora process
Hello and dead interval time:
- For P2p and Ethernet: hello 5 sec and dead 15 sec.
- For Slow links like frame relay: hello 60 sec and dead 180 sec.
Hello, message check neighbor is alive or not. Hello, message sends only when a state of Router is UP and line protocol of Router also UP. Mainly hello message use when two routers are indirectly connected.
A parameter of Hello message:
- AS number must match
- K values Must match: EIGRP uses a composite metric in hello packets with the router will tell each other what k value they are using for metric calculation. By default, K1, k3 is used but we have five k values.
- Authentication (if configured) can be different.
- Hold time: how long you have to wait for me.
This all is about for basics of EIGRP. This information helps you with the basic knowledge of EIGRP.
Find below some show command for troubleshooting:
- #To Show IP protocol summary: for this command find the running protocol on a device.
- #Show Process CPU | include EIGRP
- #To Show IP EIGRP interface: detail of EIGRP on all interface#Show IP protocol: detail about protocol
- #Show IP EIGRP interface detail F0/0: detail of EIGRP on a single interface