CCNP Network Route Part-I

EIGRP:Enhanced Interior Gateway Routing Protocol:- The most easy routing protocol of all.- It keeps backup routes- Other routing protocol only consider primary routes and forgets about the backup routes.- It is Fast routing protocol.- It is a Cisco proprietary protocol.- It has a successor and a Feasible Successor.

CCNP Network Route Part-ISuccessor:It is the primary path to the destination network.

Feasible Successor: It is the secondary path or backup path for routes or 2nd best path to the destination.

Eigrp uses Hello packets to discover neighboring routers.

Eigrp combines the characteristics of both Distance Vector and Link State routing protocol.

Distance Vector:It knows what it’s neighbor tells it.

Links state:Keeps topology table memory resident and keeps most of the database available all the time.

CCNP Network Route Part-IEigrp can perform unequal cost load-balancing, meaning it can pass 4 packets on one link and 2 packets on another link depending upon the bandwidth.

EIGRP TABLE:Every EIGRP maintains a neighbor table.This table has a list of all the neighbor routers.

EIGRP TOPOLOGY TABLE:It contains the best routes to reach the destination or know as Successor routes.It also has the 2nd best routes which is Feasible successors.

Routing Table:It contains what are the best routes available.

CCNP Network Route Part-I

EIGRP TERMINOLOGIES:

FD or Feasible Distance:It is the distance from a router to reach a specific route.e.g cost to reach the final networkExample:R1 (main router) ---(100)-R2—(10)-Final Network.

In above example cost or metric from R1 to R2 is 100 and cost from R2 to Final Network is 10 so FD (which is the distance from a router to a specific route network) would be 110.

CCNP Network Route Part-I

EIGRP TERMINOLOGIES:

AD or Advertised Distance:It is the distance from a neighbor to reach a specific route.Example:R1 (main router) ---(100)-R2—(10)-Final Network.In above example cost or metric from R2 to Final Network is 10 so AD (which is the distance from a Neighbour to a specific route or network) would be 10.

CCNP Network Route Part-I

EIGRP TERMINOLOGIES:

SUCCESSOR:These are primary routes:

FEASIBLE SUCCESSOR:These are backup routes.Rule of Feasible Successor:To become a FS (Feasible Successor) the AD (Advertised Distance) must be less than FD (Feasible Distance) of the Successor.The above rule is actually a loop prevention system.

CCNP Network Route Part-I

EIGRP TERMINOLOGIES:

ACTIVE ROUTES:This means that Router is actively looking for a backup.This is not a good sign.It is show with an “A”PASSIVE ROUTES:This means that Router is working fine and not look for any backup routes to do its job done.This is a Good signIt is shown with a “P”

CCNP Network Route Part-IEIGRP RELATIONSHIP FORMATION: (R1 & R2)Lets say R1 and R2 wish to become Neighbors via EIGRP

HELLO PACKETS:Firstly Hello Packets are exchanged among R1 & R2.A hello packet is sent from one router (R1) to its neighbor (R2) at a multicast frequency which is 224.0.0.10 (EIGRP Routers are tuned at this frequency).The Neighbor router (R2) replies and form a relationship with R1.Then the router R1 will send its entire routing table to R2 in the form of update.R2 sends update to R1.

Query:If R1 looses any routes from its routing table, it then queries its neighbor for those routes.

Reply:It’s a Reply from the neighbor.

CCNP Network Route Part-I

How EIGRP Finds the Best way around Network:It uses a formula:

K1 * BW + ((K2 * BW)/256-load) + K3 * Delay) * (K5/(reliability +K4)

Now lets define the above one by one:K1 = BANDWIDTHK2 = LOADINGK3 = DELAYK4 & K5 = RELIABILITYMostly default metric Which is only BW and Delay for calcluations.Then K1 and K3 are set to 1 and all other values are “0”So the above formula can be written as:Default Metric = 256* (slowest BW + All Link Delays)Or 256 * (k1 + k3)

CCNP Network Route Part-IDefault Metric = 256* (slowest BW + All Link Delays)Or 256 * (k1 + k3)

Slowest Link found is the slowest bandwidth. Example

R1 ---128Kbps - R2 ----64Kbps- R3----128Kbps-In above example the slowest bandwidth would be 64

Where Slowest_BW = 10^7/BW

So Default Metrick = 256 * (10 ^ 7/BW + 2000+2000+2000) Note: 2000 is default link dealy for a serialPlease refer to the the chart provided at the end of the slide.

CCNP Network Route Part-IThe below chart shows default delay EIGRP values.

Please comment,Thanks,Hyp3ri0nwww.itpings.com