Scenario: Recently MTA corporation has opened up 3 offices, you are being tasked to setup edge routers of each office. Since MTA office networks only use Cisco routers you suggested to your boss on using EIGRP. You explained the advantages of using EIGRP:
1. It is the only routing protocol that support multiple network protocols they are IP, IPX and Apple Talk.
2. It is the only routing protocol that saved the backup routes (Feasible successor) into its topology table.
3. Should there be a lost of the primary route (successor route) in the routing table the secondary route (feasible successor) will be moved from the topology table to the routing table.
4. Hence convergence is faster, and because each EIGRP does not need to maintain the big picture (as oppose to OSPF’s topology table, which contains the entire route map of the network within the same area) of the network it is not as processor intensive than OSPF.
5. While routing if a successor route is lost, EIGRP enabled routers will ask for a feasible successor route to reach the network.
Your boss is interested with EIGRP and hence asked further about the technology behind this protocol. You gladly described part of the EIGRP routing technology as follow:
There are five packets used by EIGRP to discover and maintain the network:
1. Hello: This is to discover neighbour routers and form neighbourship within the same autonomous system. Think of autonomous system as a company, when you just started work you are introduced to your new colleagues and co-working relationship is formed.
2. Query: This is the packet use to ask an alternate route (feasible successor) should the primary route (successor) is lost. When you are in doubt during work and need to accomplish a task, you will need to ask someone who may know how to advise you to accomplish your task, if that person does not know he/she will help you to find someone who may know. This is what query does.
3. Reply: This is how EIGRP responds to the query sent by neighbour. If someone ask you a question will you reply? If you do not know the answer just say “sorry I do not know” if you know tell him/her.
4. Update: When EIGRP neighbourship is formed, neighbours exchange their known route with each other, if there’s a new route of the neighbour, only the new route will be updated to the neighbour. While working with your colleagues on an existing project, all of you will brainstorm and exchange information which you know, if there’s new information that’s related to the project you share it with you team.
5. Ack: This is acknowledgment. After someone did you a favour, your politeness prompts you to say Thank you spontaneously.
EIGRP uses a math known as Diffusing Update ALgorithm (DUAL), this algorithm calculates the loop-free path.
EIGRP uses Reliable Transport Protocol to send the above 5 message packets.
EIGRP has protocol independent module, this is why EIGRP is the only routing protocol that’s able to support more than one network protocol.
EIGRP has 3 tables to keep route databases.
1. Neighbour table (show ip eigrp neighbors <asn>) . This is similar to our email address book or our personal phone book, you share information with good buddies don’t you? For EIGRP it’s the same, share updates with neighbour of the same autonomous system using RTP.
2. Topology table (show ip eigrp topology<asn> ). This is similar to your school report, report is compiled based on information you learned, heard, reading books etc… This topology table is stores the route information learned from neighbours, this contains loop-free alternatives and the best route to the destination.
3. Routing table (show ip route eigrp <asn>). Should I say more? This is the GPS with the best route plotted for you while driving 😉
Blah blah blah….
Let’s start the lab! Yawn….
1. Use EIGRP autonomous system number 100 to form route among 3 branch offices.
2. All routers should reach one another.
3. Each router should summarize its routing table to minimize the processor load of the router.
4. Make HQ router to utilize 20% more bandwidth on its serial interface than the default EIGRP bandwidth utilization.