Ccna2-Chapter4

Front 1

IGP

Back 1

Interior Gateway Protocols
-can be distance vector protocols
-can be link state routing protocols

Front 2

classful protocols

Back 2

RIP, IGRP,EGP

Front 3

classless protocols

Back 3

RIPv2, EIGRP, OSPFv2, IS-IS, BGPv4

Front 4

IPv6

Back 4

RIPng, EIGRP for IPv6, OSPFv3, IS-IS for IPv6, BGPv4 for IPv6

Front 5

Distance Vector Routing Protocols

Back 5

RIP,IGRP,RIPv2, EIGRP, RIPng, EIGRP for IPv6

Front 6

Link State Routing Protocols

Back 6

OSPFv2, IS-IS, OSPFv3, IS-IS for IPv6

Front 7

Path Vector

Back 7

EGP, BGPv4, BGPv4 for IPv6

Front 8

RIP (Routing Information Protocol)

Back 8

-distance vector routing protocol
-Hop count is used as the metric for path selection
-If the hop count for a netowrk is greater than 15, RIP cannot supply a route to that network.
-Routing updates are broadcast or multicast every 30 seconds, by default

Front 9

IGRP (Interior Gateway Routing Protocol)

Back 9

-distance routing protocol
-proprietary protocol by cisco
-Bandwidth, delay, load and reliability are used to create a composite metric
-routing updates are broadcast 90 seconds by default

Front 10

EIGRP (enhanced interior Gateway routing protocol)

Back 10

-cisco proprietary distance routing protocol
-perform unequal cost load balancing
-ituses Diffusing Update Algorithm (DUAL) to calculate shortest parth
-no periodic updates as with RIP and IGRP
-updates are sent only when there is a change in topology.

Front 11

advantages of distance vector routing protocols

Back 11

simple implementation and maintenance
Low resource requirements

Front 12

disadvantages of distance vector routing protocols

Back 12

slow convergence
limited scalability
routing loops

Front 13

routing protocol summary table

Back 13

check 4.1.4.2

Front 14

initial network discovery

Back 14

discover their own directly connected networks and subnet masks and add to routing tables.

Front 15

initial exchange of routing information

Back 15

if a routing protocol is configured, the router begins exchanging updates. When receiving updates, router checks the new info and adds what it doesn't already have in the table

Front 16

split horizon

Back 16

distance vector routing protocol implements split horizon to prevent information from being sent out the same interface from which it was received.

Front 17

convergence time

Back 17

is proportional to the size of the network

Front 18

convergence time depends on

Back 18

how quickly the router propogate a change in topology in a routing update to its neighbors
-the speed of calculating best path routes using the new routing information collected.

Front 19

age of routing information

Back 19

refreshed each time an update is received.

Front 20

change in topology can occur

Back 20

due to
-failure of a link
-introduction of a new link
-failure of a router
-change of link parameters

Front 21

3 additional timers for RIP

Back 21

- Invalid
- Flush
- Holddown

Front 22

Invalid timer

Back 22

if updates have not been received to refresh an existing route after 180 secs, the route is marked invalid by setting the metric to 16. The route is in the table till the flush timer occurs

Front 23

Flush timer

Back 23

set to 240 secs. The route marked invalid are removed at this time

Front 24

holddown timer

Back 24

stablilizes routing information and prevent routing loops when the topology is converging on new info. Once a route is marked unreachable, it must stay in holddown long enough for all routers ot learn about unreachable network. The default is 180secs.

Front 25

timer value command

Back 25

is part of show ip route and
show ip protocols

Front 26

bounded update

Back 26

updates that are sent to routers that need the information rather than to all routers.

Front 27

EIGRP

Back 27

sends bounded updates when a path changes or the metric for the route changes. The update is sent only about that network to routers that need the update.

Front 28

EIGRP updates

Back 28

-non-periodic
-partial updates sent only when there is a change in topology
-bounded updates

Front 29

triggered updates

Back 29

routing table update sent immediately in response to a routing change.

Front 30

triggered updates happen when

Back 30

-an interface changes state
- a route has entered or exited the "unreachable" state
- a route is added to the routing table

Front 31

problems with trigged updates

Back 31

-packets cnabe corrupted or dropped
-do not happen instantanteously on all routers.

Front 32

synchronized updates on a network

Back 32

cause collisions and cuase delays or consume too much bandwidth

Front 33

how to prevent collisions

Back 33

- CISCO IOS uses RIP_JITTER which subtracts a variable amount of time to the update interval for each router in the network. The variable is between 0 and 15% of the update interval.

Front 34

routing loop

Back 34

condition in which a packet is continuouly transmitted with a series of routers without ever reaching the destination network.

Front 35

cause of routing loops

Back 35

-incorrectly configured static routes
-incorrectly configure route distribution
-inconsistent routing tables not being updated due to slow convergence
-incorrectly configured or installed discard routes

Front 36

conditions that can be created by routing loops

Back 36

- link bandwidth will be used for traffic looping back and forth between routers in a loop.
-router's CPU is strained
-routers CPU is burdened with useless packet forwarding that will negatively impact the convergence of the network
-routing updates may get lost or not get processed
-packets may get lost in "black holes"

Front 37

mechanisms to eliminate routing loops

Back 37

-define a max metric to prevent count to infinity
-holddown timers
-split horizon
-route poisoning or poison reverse
-triggered updates

Front 38

count to infinity

Back 38

happens when inaccurate routing updates increase the metric value to infinity for a network that is unreachable.

Front 39

infinity value

Back 39

16 for RIP.

Front 40

holddown timer

Back 40

prevent regular update messages from reinstating a route that may have gone bad.
-this is done by holding any changes that affect a route for a specified period of time.

Front 41

split horizon

Back 41

router does not advertise a network through the interface from which the update came.

Front 42

split horizon with route poisoning

Back 42

route poisoning is used to mark a route as unreachable in a routing update that is sent to others.

Front 43

split horizon with route poison reverse

Back 43

when sending updates out a specific interface, designate any networks learned on that interface as unreachable.

Front 44

TTL (time to live)

Back 44

is the 8 bit IP header that limits the number of hops a packet can traverse through the network before discarding the packet

Front 45

features of rip

Back 45

-supports split horizon and split horizon with route poison reverse to prevent loops
-capable of load balancing

Front 46

ripv2

Back 46

-include subnet mask in updates
-authentication mechanism to secure route updates
-supports VLSM
-use multicast addresses instead of broadcast
-supports manual route summarization
-good for small networks

Front 47

EIGRP features

Back 47

-triggered updates
-topology table is used to maintain route updates
-establishment of adjancencies with neighbors using hello protocol
-support VLSM
-support route summarization
-good for large networks

Front 48

advantages of EIGRP

Back 48

-metric is based on bandwidth and delay
-fast convergence due to DUAL route calculation.
-bounded updates
-supports multiple network layer protocols