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-I Successor: It is the primary path to the destination network. Feasible Successor: It is the secondary path or backup path for routes or 2 nd 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-I Eigrp 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 2 nd 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 network Example: 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 sign It is shown with a “P”

CCNP Network Route Part-I EIGRP 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 (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 = BANDWIDTH K2 = LOADING K3 = DELAY K4 & K5 = RELIABILITY Mostly 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-I Default Metric = 256* (slowest BW + All Link Delays) Or 256 * (k1 + k3) Slowest Link found is the slowest bandwidth. Example R Kbps -  R Kbps-  R Kbps-  In above example the slowest bandwidth would be 64 Where Slowest_BW = 10^7/BW So Default Metrick = 256 * (10 ^ 7/BW ) Note: 2000 is default link dealy for a serial Please refer to the the chart provided at the end of the slide.

CCNP Network Route Part-I The below chart shows default delay EIGRP values. Please comment, Thanks, Hyp3ri0n