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CompTIA Network+ > Routing > Flashcards

Routing Flashcards

1
Q

router

A

any hardware or software that forwards packets based on their destination IP address

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2
Q

layers in each model where routers belong

A

OSI - network layer

TCP/IP - Internet layer

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3
Q

interfaces

A

at least 2 - 1 internal, 1 external

can have more

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4
Q

2 criteria in each column of the routing table

A

which packets are for the route

which port to send them out

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5
Q

destination LAN IP

A

defined network ID

every network ID directly connected to one of the router’s ports is always listed here

subnet mask is needed to define the network

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6
Q

gateway

A

IP address for next hop router

where the packet should go

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7
Q

gateway when directly connected to network

A

gateway not needed

value set to 0.0.0.0 or IP address or directly connected port

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8
Q

gateway when not directly connected to network

A

gateway column of the routing table tells the router the IP address of a router to send packet to

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9
Q

interface

A

tells router which of its ports to use

LAN / WAN

Port IP

fa0/0 & fa0/0 - Cisco

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10
Q

0 in routing table

A

means “anything”

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11
Q

default route (example)

A

[0.0.0.0] [0.0.0.0] [70.30.4.1] [WAN]

any destination address

with any subnet mask

forward to 70.30.4.1

using WAN port

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12
Q

default route (importance)

A

tells router what to do with every incoming packet unless another line in the routing table gives another route

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13
Q

2 places where routers do not have default routes

A

private internetworks - every router knows every network

tier 1 Internet backbone

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14
Q

other devices with routing tables

A

all TCP/IP capable devices

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15
Q

command to display routing table

A

netstat -r (OS X & Windows)

route print (Windows)

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16
Q

metric

A

relative value that defines the cost of using a particular route

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17
Q

adding interfaces to a router

A

removable modules are available for more powerful routers

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18
Q

NAT

A

network address translation

enables routers to hide internal IP addresses while still allowing communication with the broader Internet

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19
Q

how NAT functions

A

router replaces the source IP address of a computer is its outside interface address on outgoing packets

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20
Q

basic NAT

A

translates the private / internal IP address to the global IP address on 1-1 basis

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21
Q

primary reason NAT was created & conception of what it does

A

address the problem of limited IPv4 addresses

security / anonymity

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22
Q

PAT

A

port address translation

uses port numbers to route traffic from specific machine in the network

most common form of NAT that handles 1-to-many connections

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23
Q

how PAT functions

A

internal machine initiates a session with an external machine

source & destination IP addresses & port numbers for TCP segment / UDP datagram are recorded in PAT’s translation table

private IP address is swapped for public IP address on each packet

port number used by the internal computer for the session is also translated into a unique port number that is also recorded by router

receiving system returns packet - reverses IP addresses & ports

router compares incoming destination IP address & port number and compares to translation table - puts correct IP back on packet

sends to correct computer

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24
Q

PAT limitation

A

only works for outgoing communication, not incoming communication

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25
Q

SNAT

A

static NAT

maps a single routable (not private) IP address to a single machine

enables access to that machine from outside the network

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26
Q

port forwarding

A

designate a specific local address for various network services

request a service using the public IP address of the router & the port number of the desired service

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27
Q

how port-forwarding routers work

A

examines the packet & compares to list of services mapped to local addresses

sends packet to appropriate computer

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28
Q

hiding hosted services inside network

A

change default port number for that service

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29
Q

DNAT

A

many computers can share a pool of routable IP addresses that number fewer than the number of computers

LAN traffic uses internal IP

NAT distributes routable IP from the pool for external requests

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30
Q

metrics only work when

A

there are direct connections between network IDs

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31
Q

hop

A

each time a packet goes through a router

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32
Q

metric

A

relative value that routers use when they have more than one route to get to another network

router always chooses route with lowest metric

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33
Q

most common criteria for determining a metric

A

hop count

bandwidth

latency

cost

MTU

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34
Q

how many hops with 3 intermediate routers

A

4

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35
Q

latency

A

collective term that describes the large number of issues that may occur between routers that slow down network connections

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36
Q

MTU

A

maximum transmission unit

largest frame a particular technology can handle

37
Q

Ethernet frame size

A

1,500 bytes

38
Q

fragmentation

A

packet is too large for a technology to handle

broken down to fit in network’s protocol

slows down movement of packets

39
Q

way to limit fragmentation

A

set optimal MTU size before sending packets

40
Q

administrative distance

A

metric used by routers that use multiple protocols & thus can have multiple paths to the same destination

41
Q

SPB

A

shortest path bridge

routing metric standard to provide true shortest-path forwarding within Ethernet mesh topology

supports large layer 2 networks by providing fast convergence & multiple, equal cost paths

42
Q

distance vector routing protocols (definition)

A

calculate the total cost to a network ID & compare to the totals cost of all other routes to that network ID

router chooses lowest cost route

43
Q

distance vector routing protocols

A

total cost = hops between router & network

1 hop = cost of 1

can manually set cost of slower routes to 10

44
Q

distance vector routing protocols - transfer of routing tables

A

routers transfer their entire routing table to other routes in the WAN

each protocol has a maximum number of hops that it will send its routing table to limit traffic

45
Q

convergence

A

steady state

process of updating routing tables has been completed

46
Q

distance vector routing protocols - convergence

A

routing tables are shared & updated

all but lowest total cost route are deleted from table

updated tables are shared again

all routers only have the lowest total cost routes saved

47
Q

distance vector routing protocols - limitation

A

smaller networks - less than 10 routers

convergence would take too long

48
Q

distance vector routing protocols - specific protocols

A

RIPv1

RIPv2

BGP

49
Q

RIPv1

A

routing information protocol

max hop count = 15

every router sent updates every 30 seconds - bogged down networks

no authentication used

50
Q

RIPv2

A

routing information protocol

current version of RIP

incorporates VLSM & uses authentication

otherwise works the same as RIPv1

51
Q

VLSM

A

variable-length subnet masking

networks connected via a router use different subnet masks

52
Q

AS

A

autonomous system

1 or more networks that are governed by a single dynamic routing protocol

use ASN rather than IP addresses

2 16-bit numbers separated by a dot (1.33457)

53
Q

ASN

A

autonomous system number

globally unique identifier assigned by IANA

54
Q

EGP

A

exterior gateway protocol

used by AS’s to communicate with each other

55
Q

IGP

A

interior gateway protocol

used by the network(s) within an AS to communicate with each other

56
Q

border gateway protocols

A

many used within AS’s i.e. RIP

BGP-4 is standard for communication between AS’s of the Internet

57
Q

exam classification of BGP

A

hybrid protocol

more accurately a path vector protocol

58
Q

configuration of BGP routers

A

manual

don’t go down often

59
Q

edge routers

A

AS to AS routers

pass / advertise information i.e. ASN & other non-IP items

60
Q

route aggregation

A

backbone routers track location of routers that connect to subsets of locations

way to simplify routing tables into manageable levels

supported by BGP

61
Q

iBGP & eBGP

A

internal BGP & exterior BGP

BGP can be used to connect routers within an AS

62
Q

link state dynamic routing protocol

A

only announce & forward individual route changes instead of entire routing table

OSPF & IS-IS

63
Q

OSPF

A

open shortest path first

most commonly used IGP on Internet

designed to work within a single AS

much faster convergence

64
Q

LSA

A

link state advertisements

packets sent by OSPF-capable routers to find other OSPF routers

“hello packets”

used to update link state databases

65
Q

flooding

A

transmission of a lot of LSA packets when a router first comes online

66
Q

determining OSPF cost

A

speed of the link

100,000,000 / bandwidth in bps

10BaseT 100,000,000 / 10,000,000 = 10

67
Q

areas

A

groupings of routers to limit excessive broadcast while scaling up a network

68
Q

backbone

A

central area in a network of interconnected areas

assigned area ID

all traffic between areas goes through backbone

69
Q

area ID

A

0 or 0.0.0.0

70
Q

ABRs

A

area border routers

special routers that interconnect areas

71
Q

frequency of hello LSAs upon convergence

A

~ 30 minutes

unless break is detected in link state

72
Q

break in link state is detected

A

routers attempt to reconnect > unsuccessful

routers send LSA announcing broken connection

each router updates table to remove broken route

73
Q

benefits of OSPF

A

provides authentication

prevents loops

protocol of choice for large enterprise networks

74
Q

IP version support in OSPF

A

OSPFv2 supports IPv4

OSPFv3 supports IPv6

75
Q

IS-IS

A

intermediate system to intermediate system

very similar to OSPF

IPv6 compatible from the start

standard for ISPs - rare to see in practice

76
Q

EIGRP

A

enhanced interior gateway routing protocol

developed by Cisco

“advanced distance vector protocol”

aspects of distance vector & link state protocols

77
Q

route redistribution

A

router takes a route it has learned from 1 protocol & announces that route over another protocol

routers can’t communicate with different protocols

can use multiple protocols simultaneously to perform route redistribution

78
Q

connecting to a router

A

serial connection - Cisco - rollover or Yost cable

usb

RJ-45

79
Q

managed devices

A

advanced switches & routers that require configuration

80
Q

method of configuring router once connected

A

terminal emulation programs i.e. PuTTY & HyperTerminal

81
Q

basic settings for serial connections

A

9,600 baud

8 data bits

1 stop bit

no parity

82
Q

console

A

screen you type into in a terminal emulation program

83
Q

NMS

A

network management software

software that interfaces with network hardware to provide an overall view of the network

84
Q

[blank] are configured to use protocols

A

individual NICs - not entire routers

protocols must match

85
Q

common source of routing problems

A

error in routing table

86
Q

commands for investigating routes

A

tracert - Windows

traceroute - Unix/Linux

87
Q

traceroute no longer works

A

something wrong between your router and the next router upstream

88
Q

mtr

A

my traceroute

continuous Linux tool

89
Q

pathping

A

Windows tool that computes performance over a set amount of time & displays summary

CompTIA Network+ (9 decks)

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