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All rights reserved. No part of this document or the related files may be reproduced or transmitted in any form, by any means electronic, photocopying, recording, or otherwise without the prior written permission of the publisher. Limit of Liability and Disclaimer of Warranty: The publisher has used its best efforts in preparing this book, and the information provided herein is provided "as is.
Trademarks: This book identifies product names and services known to be trademarks, registered trademarks, or service marks of their respective holders. They are used throughout this book in an editorial fashion only. Use of a term in this book should not be regarded as affecting the validity of any trademark, registered trademark, or service mark. The problem with networking is that you need to know what you are doing before you can configure anything.
Even if you have all the commands you still need to understand what and why you are typing these commands. I have tried to put all the important keywords in bold.
One last thing before we get started. Notes are just lists with random information while mindmaps show the relationship between the different items.
If you have any questions or comments about this book, please let me know: E-mail: info gns3vault. Introduction to OSPF. OSPF Summarization. OSPF Authentication. Routing Manipulation. BGP Attributes and Path selection. Introduction to IPv6. IPv6 Routing Protocols. Final Thoughts. If you want routing with devices from different vendors like Juniper you will have to look for another routing protocol.
Cisco added some of the features from link-state routing protocols to EIGRP which makes it far more advanced than a true distance vector routing protocol like RIP. This is why probably the marketing department calls EIGRP an advanced distance vector or hybrid routing protocol. EIGRP does not use broadcast packets to send information to other neighbors but will use multicast or unicast. EIGRP has its own protocol number which is EIGRP routers will start sending hello packets to other routers just like OSPF does, if you send hello packets and you receive them you will become neighbors.
EIGRP neighbors will exchange routing information which will be saved in the topology table. The best path from the topology table will be copied in the routing table. We are going to calculate the best path to the destination which is behind router Carl.
EIGRP uses a rich set of metrics namely bandwidth, delay, load and reliability which we will cover later. These values will be put into a formula and each link will be assigned a metric. The lower these metrics the better. Router Carl will advertise to router Ann its metric towards the destination. This is called the advertised distance.
We know the advertised distance is 5 since this is what router Carl told us. We also know the metric of the link between router Ann and router Carl since this is directly connected. Router Ann now knows the metric for the total path to the destination, this total path is called the feasible distance and it will be saved in the topology table. The advertised distance, your neighbor tells you how far it is for him to reach the destination and the feasible distance which is your total distance to get to the destination.
Router Ann is sending its feasible distance towards router KingKong which is Router KingKong will save this information in the topology table as the advertised distance.
This information is saved in the topology table. The best path to the destination is called the successor! The successor will be copied from the topology table to the routing table. How do we find out if we have a feasible successor? Router KingKong is telling us the destination is 10 away, router Ann tells us its 5 away and router Carl tells us its 9 away. Advertised Distance Feasible distance KingKong 10 15 Ann 5 10 Carl 9 The path with the lowest feasible distance will be the successor router Ann so now we answered the first question.
The advertised distance of router Carl is 9 which is lower than the feasible distance of router Ann which is Router Carl will be a valid feasible successor and used as a backup path!
You will find both entries in the EIGRP topology but you will only find the successor in the routing table. Now look closely to the feasible distance of router Carl and router KingKong…what do you see? Does this make any sense? Nope this is perfectly the way it should be! Distance vector routing protocols only know which way to go vector and how far away the destination is distance.
EIGRP has another trick in its hat. EIGRP can do something cool…unequal load balancing! Even better it will share traffic in a proportional way, if you have a feasible successor that has a feasible distance which is 5 times worse than the successor traffic will be shared in a way. If you look at the routing table you will only find the successor there. You can do this by using the variance command.
In order to load-balance our feasible successor needs to have a lower feasible distance than the successor X multiplier. Are we ever going to use the route through router KingKong? Router Spade will advertise the destination network to router Hearts. Router Hearts will advertise the network to router Clubs and Diamond. Router Clubs will advertise the network to router Diamond. Router Diamond will advertise the network to router Clubs. Router Clubs will advertise this network back to router Hearts.
Router Diamond will advertise this network back to router Hearts. Advertised Distance Feasible distance Spade 5 Clubs 25 Diamond 19 Here we have the advertised distance; our neighbors are telling us how far it is for them to reach the destination network. Next step is to fill in the feasible successors. How did I get the numbers in the advertised distance table? The destination has a distance of 5 as seen in the topology picture. This will be advertised to router Hearts and placed in its topology table.
Router Clubs will learn the destination network through router Hearts and router Diamond. Good question! Remember split-horizon? How did I get to 25? The same thing applies for the advertised distance of 19 for router Diamond: 1.
Router Spade advertises a distance of 5 to router Hearts. Last step is to pick our successor. This makes sense right? If these routers become backup paths we would have a loop! What do you think? Was this new for you or just CCNA refreshment? Make sure you understand all the key concepts because in the next chapter we are going to dive deeper into the material. If you send hello packets and receive them then EIGRP will form a neighbor relationship with the other router.
It can use multicast or unicast and to keep things efficient not all packets are sent reliable. Reliable means that when we send a packet we want to get an acknowledgment from the other side to make sure that they received it.
Hello packets are sent between routers in order to form adjacencies. As you can see router Lizzy is sending 3 hello packets meant for router Jack, John and Lizzy. Sending 3 packets on the same link is not very useful so instead of doing this EIGRP will send hello packets by using multicast on a multi-access network like Ethernet.
As soon as you send hello packets and receive them your EIGRP routers will try to form the neighbor adjacency. Update packets have routing information and are sent reliable to whatever router that requires this information. Update packets can be sent to a single neighbor using unicast or to a group of neighbors using multicast. What happens is that your router will send query packets to its neighbors asking them if they have information about this particular network.
Reply packets are used in response to the query packets and are reliable. ACK packets are used to acknowledge the receipt of update, query and replay packets. ACK packets are sent by using unicast. The first one is the neighbor table and this is where EIGRP stores all information of directly connected neighbors.
After we have become neighbors routers will exchange routing information which is stored in the EIGRP topology table. As soon as we enable it for the interface they will start sending hello packets.
Book Review: How to Master CCNP Route
Before you start with this…. Scenario: The fermentum corporation has hired you to troubleshoot their international network that consists of BGP routers. There are a number of issues. Some BGP routers are unable to establish a neighbor adjacency and others are having issues….