Eigrp

Front 1

EIGRP is a LS or DV protocol?

Back 1

Neither, it is a hybrid

Front 2

EIGRP is open standards / propietary?

Back 2

Proprietary

Front 3

Topology table

Back 3

A table that contains all the paths advertised by neighbors to all the known networks. This is a list of all the successors, feasible successors, the feasible distance, the advertised distance, and the outgoing interface. DUAL acts on the topology table to determine successors and feasible successors by which to build a routin table.

Front 4

when is a update sent?

Back 4

• When a neighbor first comes up
• When a neighbor transitions from active to passive for a
destination
• When there is a change in calculated metric for a destination

Front 5

Query

Back 5

Sent from the router when it loses a path to a network. If there is no alternate route (feasible successor), it will send out queries to neighbors inquiring whether they have a feasible successor.

Front 6

SRTT

Back 6

Smooth Round-Trip Time
The time that the router waits after sending a packet reliably to hear an acknowledgment. This is held in the neighbor table and is
used to calculate the RTO.

Front 7

RTO

Back 7

Retransmission Timeout
Timer calculated in reference to the SRTT. RTO determines howlong the router waits for an ACK before retransmitting the packet.

Front 8

RTP

Back 8

Reliable Transport Protocol
Mechanism used to determine requirements that the packets be
delivered in sequence and guaranteed.

Front 9

DUAL

Back 9

Diffusing Update Algorithm
An algorithm performed on the topology table to converge the
network. It is based on a router detecting a network change within a finite time, with the change being sent reliably and in sequence.
As the algorithm is calculated simultaneously, in order, and
within a finite time frame on all affected routers, it ensures a loop-free network.

Front 10

AD

Back 10

Advertised distance
The cost of the path to the remote network from the neighbor (the metric from the next-hop router).

Front 11

FD

Back 11

Feasible distance
The lowest-cost distance (metric) to a remote network.

Front 12

FC

Back 12

Feasible condition
When a neighbor reports a path cost (AD) that is lower than the
router’s FD to a network.

Front 13

FS

Back 13

Feasible successor
The neighbor reporting the AD that is lower than the router’s FD becomes the feasible successor. The next-hop router that meets
the FC.

Front 14

Successor

Back 14

The next-hop router that passes the FC. It is chosen from the FSs as having the lowest metric to the remote network.

Front 15

SIA

Back 15

Stuck in Active
State reached when a router has sent out network packets and is waiting for ACKs from all its neighbors. The route is active until all the ACKs have been received. If they do not appear after a certain time, the router is SIA for the route.

Front 16

Query scoping

Back 16

Network design to limit the scope of the query range, that is, how far the query is allowed to propagate in search of a feasible successor. This is necessary to prevent SIA, which can cause multiple problems for the network.

Front 17

Active

Back 17

Route state when there is a network change, but after examining the topology table, no FS is found. The route is set to active mode, and the router queries its neighbors for alternative routes.

Front 18

Passive

Back 18

An operational route is passive. If the path is lost, the router examines the topology table to find an FS. If there is an FS, it is placed in the routing table; otherwise, the router queries its neighbors, sending the route into active mode.

Front 19

EIGRP increases the potential growth of a network by reducing the convergence time using what features?

Back 19

■ DUAL
■ Loop-free networks
■ Incremental updates
■ Multicast addressing for updates
■ Loop-free routing tables
■ Support for different topologies
■ Rapid convergence
■ Reduced bandwidth use
■ Protocol independence at Layer 3
■ Compatibility with IGRP
■ Easy configuration
■ Use of a composite metric
■ Unequal-cost load balancing
■ Advanced distance vector protocol

Front 20

four main components of EIGRP:

Back 20

■ Protocol-dependent modules
■ RTP
■ Neighbor discovery and recovery
■ DUAL

Front 21

There are three main tables in EIGRP:

Back 21

■ The neighbor table
■ The topology table
■ The routing table

Front 22

The neighbor table is maintained by means of ________

Back 22

the hello protocol

Front 23

The neighbor table includes the following information:

Back 23

■ The address of the neighbor.
■ The interface through which the neighbor’s Hello was heard.
■ The holdtime, or how long the neighbor table waits without hearing a Hello from a neighbor,
before declaring the neighbor unavailable and purging the database. This is three times the value of the Hello timer by default.
■ The uptime, or how long since the router first heard from the neighbor.
■ The sequence number.
It tracks both the last sequence number sent to the neighbor and the last sequence number received from the neighbor.
■ SRTT. This calculates the RTO. This is the time in milliseconds that it takes a packet to be sent to a neighbor and a reply to be received.
■ RTO. This states how long the router will wait on a connection-oriented protocol without an acknowledgment before retransmitting the packet.

Front 24

If the original packet that was unacknowledged was multicast, the retransmitted packets will be

Back 24

unicast.

Front 25

The EIGRP Hello protocol uses a multicast address of

Back 25

224.0.0.10

Front 26

To become a neighbor, the following conditions must be met:

Back 26

■ The router must hear a Hello packet or an ACK from a neighbor.
■ The autonomous system number in the packet header must be the same as that of the receiving router.
■ The neighbor’s metric settings must be the same as that of the receiving router.

Front 27

The topology table includes the following information:

Back 27

■ Whether the route is passive or active.
■ That an update has been sent to the neighbors.
■ That a query packet has been sent to the neighbors. If this field is positive, at least one route will
be marked as active.
■ If a query packet has been sent, another field will track whether any replies have been received from the neighbors.
■ That a reply packet has been sent in response to a query packet received from a neighbor.
■ The remote networks.
■ The prefix or mask for the remote network.
■ The metric for the remote network, the FD.
■ The metric for the remote network advertised by the next logical hop, the AD.
■ The next hop.
■ The outgoing interface to be used to reach the next logical hop.
■ The successors, the path to the remote network stated in hops.

Front 28

The three reasons that might cause a topology table to be recalculated:

Back 28

■ The router hears a change when a new network is available
■ The router changes the successor in the topology table and routing table
■ The router hears a change from a neighbor when a network has become unavailable

Front 29

The router hears a change when a new network is available because of one of the following
reasons:

Back 29

— The topology table receives an update stating that there is a new remote network.
— The interface for a directly connected EIGRP network comes online.

Front 30

The router changes the successor in the topology table and routing table in these circumstances:

Back 30

— The topology table receives a reply or a query from a neighbor.
— There is local configuration of a directly connected interface to change the cost of the link.

Front 31

The router hears a change from a neighbor when a network has become unavailable because of
one of the following reasons:

Back 31

— The topology table receives a query, reply, or update stating that the remote network
is down.
— The neighbor table does not receive a Hello within the holdtime.
— The network is directly connected, and the router senses a loss of carrier.

Front 32

The main difference between the metrics used in EIGRP and IGRP =

Back 32

Is the calculation is held in a 32-bit field.

Front 33

EIGRP Routing Types

Back 33

Internal
Internal paths to the autonomous system

Summary
Internal paths that have been summarized

External
External paths to the autonomous system that have been redistributed into this EIGRP autonomous system

Front 34

The equation for the default metric used is this:

Back 34

metric = [(10000000  smallest bandwidth kbps) + sum of delays] * 256

Front 35

EIGRP Metric Values:
K1
K2
K3
K4
K5

Back 35

Bandwidth
Loading
Delay
Reliability
MTU

Front 36

what is the metric Delay?

Back 36

The delay calculated on the outgoing interface. The value used is
the cumulative total of the delay on all the interfaces between the
hosts. The delay is measured in units of 10 ms to 168 seconds. A delay of all 1s in the 32-bit field means the network is unreachable.

Front 37

The default for the K constants are
K1
K2
K3
K4
K5

Back 37

K1 = 1,
K2 = 0,
K3 = 1,
K4 = 0,
K5 = 0

Front 38

The metric or cost from the neighbor advertising the route is known as the

Back 38

advertised distance

Front 39

The metric or cost from the router that is determining the metric or the local router is referred to as

Back 39

feasible distance

Front 40

A neighbor can become an FS for a route only if its __ is less than the __.

Back 40

AD
FD

Front 41

The factors that can affect the scaling of EIGRP are as follows:

Back 41

■ The amount of information sent between neighbors
■ The number of routers that are sent updates
■ How far away the routers are that have to send updates
■ The number of alternative paths to remote networks

Front 42

Poorly scaled EIGRP networks can result in the following:

Back 42

■ A route being SIA
■ Network congestion
■ Router memory running low
■ Router CPU overutilized
■ Unreliable circuit or unidirectional link

Front 43

Solutions to EIGRP Scaling Issues

Back 43

■ Allocation of addresses should be contiguous to allow summarization.
■ A hierarchical tiered network design should be used to allow summarization.
■ Sufficient network resources (both hardware and software) on network devices.
■ Sufficient bandwidth should be used on WAN links.
■ Appropriate EIGRP configuration should be used on WAN links.
■ Filters should be used.
■ Network monitoring should be used.