1. EIGRP

2. Introduction to EIGRP
advanced distance vector routing protocol developed by Cisco Systems.
IGRP is an older classful, distance vector routing protocol.
includes features found in link-state routing protocols.
suited for many different topologies and media.
scale to include multiple topologies and can provide extremely quick convergence times with minimal network traffic.
EIGRP became a multi-vendor routing protocol.
Has a composite metric
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3. DUAL Diffusing Update Algorithm.
DUAL guarantees loop-free and backup paths throughout the routing domain. 
Using DUAL, EIGRP stores all available backup routes for destinations so that it can quickly adapt to alternate routes when necessary. Fast convergence time
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4. Features of EIGRP Establishing Neighbor Adjacencies .
Reliable Transport Protocol.
 flexible and can be used for protocols other than those from the TCP/IP
Partial Updates.
update only includes information about the route changes, such as a new link or a link becoming unavailable.
Does not age out entries
Bounded Updates
propagation of partial updates are sent only to those routers that the changes affect. 
This minimizes the bandwidth that is required to send EIGRP updates.
Equal and Unequal Cost Load Balancing
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5. Autonomous System number
EIGRP uses the router eigrp autonomous-system command to enable the EIGRP process. 
Is only significant to the EIGRP routing domain.
It functions as a process ID to help routers keep track of multiple running instances of EIGRP. 
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6. Autonomous System number
The autonomous-system argument can be assigned to any 16- bit value between the number 1 and 65,535.
All routers within the EIGRP routing domain must use the same autonomous system number
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7. Router ID
The EIGRP router ID is used to uniquely identify each router in the EIGRP routing domain.
EIGRP for IPv4 uses the 32-bit router ID to identify the originating router for redistribution of external routes.
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8. Router ID
1. Use the address configured with the eigrp router-id ipv4- address router configuration mode command.
2. If the router ID is not configured, choose the highest IPv4 address of any of its loopback interfaces.
3. If no loopback interfaces are configured, choose the highest active IPv4 address of any of its physical interfaces.
A loopback address is a virtual interface and is automatically in the up state when configured.
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9. Encapsulation Frame header IP packet header EIGRP packet header
Type/ length/ value data
Opcode AS number
If Ethernet, destination MAC address multicast E A.
EIGRP Parameters, IP Internal Routes, IP External Routes.
Protocol field 88 destination address multicast
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10. EIGRP packet header
EIGRP packet header
Opcode specifies packet type: Update, Query, Reply, Hello
Autonomous system (AS) number specifies the EIGRP process. Several can run at the same time.
Other fields allow for reliability if needed.
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11. EIGRP TLV field Type/ length/ value data
Values needed for calculating metric
K1 value, default 1, weighting for bandwidth
K2 value, default 0, weighting for
K3 value, default 1, weighting for delay
K4 value, default 0, weighting for
K5 value, default 0, weighting for
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12. EIGRP TLV field Type/ length/ value data Hold time:
The number of seconds a router should wait for a hello message before considering that a neighbour router is down.
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13. Internal routes
Type/ length/ value data
Internal routes originate within the AS.
Their messages include
metric information: bandwidth, delay, load, reliability
prefix length and network address
Next hop address
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14. External routes Type/ length/ value data
External routes originate elsewhere and are imported. (Static, other protocol, other AS)
Their messages include all the internal route information.
Plus extra fields used to track the source of the information.
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15. Metrics
Bandwidth
Bandwidth is the capacity of a wired or wireless network link to transmit the maximum amount of data from one point to another in a given amount of time.
Bandwidth is usually considered as the lowest configured bandwidth on any interface on the route.
You should always configure a bandwidth value on an interface when using EIGRP, otherwise a default is used.
Take the lowest bandwidth value in the path.
Calculate (10,000,000/bandwidth) * 256
This is the bandwidth part of the metric.
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16. Administrative Distance (AD)
Administrative distance is the feature that routers use in order to select the best path when there are two or more different routes to same destination from two different routing protocols.
Administrative distance defines the reliability of a routing protocol.
Each routing protocol is prioritized in order of most to least reliable with the help of an administrative distance value.

17. Metrics
Delay: is how long it takes for a bit to travel across the network from one node to another.
It includes the following: (Processing– Queuing-Transmission – Propagation)
Delay is calculated as the sum of delays from source to destination in units of 10 microseconds.
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18. EIGRP metric Bandwidth and delay are used by default.
Load and reliability can be used too.
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19. K values EIGRP metric weight:
Show ip protocols will show the K values.
EIGRP metric weight:
K1(bandwidth)=1, K2(Load)=0, K3(Delay)=1, K4(Reliability)=0,K5(Reliability)=0
Metric= Bandwidth + Delay
Metric= [K1*”bandwidth”]+[K3*”delay”]
Metric = [K1* “(10,000,000/bandwidth) * 256”] [K3*”(sum of delay/10)* 256”]
Leave K’s alone unless there is a very good reason to change them.
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20. Delay
Delay is a measure of the time it takes for a packet to traverse a route.
Delay is not measured dynamically.
Default values are used, e.g.
Serial interfaces 20,000 microseconds
FastEthernet interfaces 100 microseconds
The delay value can be changed.
Find the delay value on every outgoing interface along the path.
Delay metric = (sum of delay/10)* 256
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21. Example step 1 Metric to this network? BW1 1,024 Kbps delay1 20000
Best route (Path)
What is the bandwidth of the above route?
BW1= 1024 Kbps > BW2 = 100,000 Kbps BW = 1024 Kbps
(The smallest bandwidth along the route is chosen as the bandwidth of the route)
Bandwidth metric = (10,000,000/1024)*256
Round 10,000,000/1024 to a whole number before multiplying by 256
Bandwidth metric = 2,499,840.
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22. Example step 2 Metric to this network? BW1 1,024 Kbps delay1 20000
Best route (Path)
Delay metric = (sum of delay/10)* 256
= (20100/10)*256 =
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23. Example step 3 Metric to this network? BW1 1,024 Kbps delay1 20000
Best route (Path)
Bandwidth metric = 2,499,840
Delay metric =
Bandwidth + delay =
This is the metric calculated by the router on the left.
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24. Reliability and Load
Reliability is measured dynamically. It measures the frequency of errors and the probability that the link will fail.
255 is totally reliable, 0 is totally unreliable.
Not a default EIGRP metric.
Load is measured dynamically. It shows the amount of traffic using the link.
1/255 is minimal load. 255/255 is fully saturated.
Both transmit and receive load are measured.
Not a default EIGRP metric
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25. DUAL terminology
D /24 [90/ ] via , 00:00:31, Serial0/0/1
Interface of successor router that provides the next hop on the best path.
Feasible distance: the metric of the best path.
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26. DUAL terminology destination FD 3014400 RD 28160 FD 28160
Reported distance: the metric that a neighbour (closer to the destination) reports for a route. This is the neighbours feasible distance for the route.
destination
FD RD 28160
FD 28160
FD RD
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27. Feasibility condition (FC)
This condition is met if the reported distance (RD) to a network, learned from a neighbour, is less than the router’s own feasible distance.
30720 no
destination
yes
28160
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28. Feasible successor (FS)
A feasible successor (FS) is a neighbour who has a path to the same network as the successor, and satisfies the feasibility condition.
This path should be loop-free and is kept as a backup path.
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29. Topology table
P /24, 1 successors, FD is via ( /28160), Serial0/ via ( / ), Serial0/0
Lists all successors and feasible successors (backup routes)
Gives feasible distance and reported distance
Note that reported distance of backup route is less than feasible distance of successor.
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30. Topology table – passive/active
P /24, 1 successors, FD is via ( /28160), Serial0/ via ( / ), Serial0/0
P is for passive. The route is stable, not being recalculated, therefore it can be used.
A means active. An active route is in the process of being recalculated by DUAL and cannot be used.
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31. Network layer protocols
EIGRP can support more than one network layer protocol, e.g. IP, IPX, Appletalk.
It has protocol dependent modules to support the different network layer protocols.
It keeps separate routing tables, neighbor tables and topology tables for the different network layer protocols.
The main EIGRP software is independent of the network layer protocol.
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32. Reliable Transport Protocol
RTP is used instead of TCP and UDP.
It can provide reliability like TCP by means of acknowledgements.
It can send some packets unreliably like UDP.
TCP and UDP are not used because that would tie EIGRP to the TCP/IP suite, and it was designed to be independent.
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33. Protocol dependent modules
IPX PDM
IP PDM
Appletalk PDM + + +
DUAL
Neighbour discovery
RTP
DUAL
Neighbour discovery
RTP
DUAL
Neighbour discovery
RTP
IPX encapsulation
IP encapsulation
Appletalk encapsulation
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34. EIGRP Packet Types
Hello packets - Used for neighbor discovery and to maintain neighbor adjacencies.
Sent with unreliable delivery
Multicast
Holdtime=3× helloInterval
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35. EIGRP Packet Types
Update packets - Propagates routing information to EIGRP neighbors. (partial update, bounded update)
Sent with reliable delivery
Unicast or multicast
Acknowledgment packets
Sent with unreliable delivery
Unicast
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36. EIGRP Packet Types Query packets -
Sent with reliable delivery
Unicast or multicast
Reply packets - Sent in response to an EIGRP query.
Unicast
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37. EIGRP Packet Types
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38. Subnet mask, wildcard mask - -
Subnet mask Wildcard mask - -
Subnet mask Wildcard mask
Wildcard mask is the inverse of the subnet mask
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39. Feasibility condition Link down and switching to the backup route
Feasible successor
Feasibility condition
Link down and switching to the backup route
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