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CCNA > Routing > Flashcards

Routing Flashcards

1
Q

configure router subinterface

A
  • i.e. interface f-/0.10
  • encapsulation dot1q 10
  • ip and mask
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2
Q

configure static route

A

ip route network-address mask {ip | exit interface}

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3
Q

default route

A

static routed used w/ bits matching

configured as 0.0.0.0 0.0.0.0

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4
Q

configure RIP

A 
#router rip
#network *ip address*
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5
Q

RIP troubleshooting commands

A

show ip route

show ip protocols

show ip rip

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6
Q

switch router to RIPv2

A 
#router rip
#version 2
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7
Q

enable VLSM for RIPv2

A

no auto-summary

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8
Q

EIGRP

A
  • distance vector
  • classless
  • cisco proprietary
  • RTP
  • bounded updates
  • diffusing update algorithm (DUAL)
  • establishing adjacencies
  • neighbor and topology table
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9
Q

EIGRP TLV types (type/length/value)

A

0x0001 EIGRP parameters
0x0102 IP internal routes
0x0103 IP external routes

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10
Q

Opcode in EIGRP header

A

specifies EIGRP packet type

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11
Q

AS # in EIGRP packet header

A

specifies antonymous system # since multiple EIGRP instances can be run

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12
Q

5 EIGRP packet-types

A
  • hello
  • update
  • acknowledgement
  • query
  • reply
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13
Q

configure EIGRP summary route

A

enter interface config mode

ip summary-address eigrp as-# network# mask

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14
Q

command to include static route in routing updates

A

redistribute static

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15
Q

command to modify bandwidth metric on EIGRP interface

A

bandwidth speed in kilobits

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16
Q

3 tables useful for troubleshooting EIGRP

A
  • routing table
  • neighbor table
  • topology table
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17
Q

sucessor

A

neighboring router used for packet forwarding and is the least-cost route to the destination network

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18
Q

feasible distance

A

lowest calculated metric to destination network

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19
Q

feasibility

A

met when neighbors reported distance to a network is less than the local routers FD to the same network

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20
Q

OSPF

A

Open Shortest Path First

  • link state protocol
  • open standard
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21
Q

5 OSPF packet types

A

-hello
-DBD (database description)
-LSR (link-state request)
-LSU (link-state update)
LSAck (link state acknowledgement)

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22
Q

OSPF hello packets

A
  • discover OSPF neighbors & establish adjacencies
  • advertise parameters on which 2 routers must agree to become neighbors
  • elect the designated router & backup designated router on multiaccess networks
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23
Q

matching interface values required for OSPF adjacency

A
  • hello interval
  • dead interval
  • network type
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24
Q

designated router

A
  • responsible for updating all other OSPF routers on a multi-access network
  • router w/ highest OSPF interface priority is chosen
  • 2nd highest is backup designated router
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25
Q

link state routing process

A
  • each router learns about its own links
  • each router uses hello packets to establish adjacencies
  • each router builds a link-state packet
  • each router floods the LSP to all neighbors
  • each router uses the database to construct a complete map of the topology, SPF determines the best paths
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26
Q

command to enable OSPF

A 
#router ospf process-id
#network address wildcard mask area area-id
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27
Q

OSPF area

A

group of routers that share link-state information

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28
Q

OSPF metric

A

cost

10 to the 8th/bandwidth in bps

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29
Q

modify OSPF bandwidth

A

use bandwidth command to modify bandwidth value

use ip ospf cost command

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30
Q

change router OSPF priority to control DR & BDR selection

A

ip ospf priority {0-255}

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31
Q

basic routing troubleshooting

A
  • check routing tables for convergence using show ip route
  • ip routes are missing investigate protocol operation using show ip protocols
  • check for missing neighbors using show ip (ospf or eigrp) neighbors
  • show run config
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32
Q

troubleshooting VLSM

A
  • pay attention to see if design really uses VLSM, check for classless routing protocol
  • check for overlapping subnets
  • outward symptoms include not sending packets out of local subent
  • use traceroute
  • do the math on subnets to be sure they don’t overlap
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33
Q

troubleshoot RIP

A
  • incorrect network statements

- dis-contiguous networks

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34
Q

EIGRP and OSPF troubleshooting commands

A

show ip eigrp interfaces

show ip ospf interface brief

show ip protocols

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35
Q

configure DHCP server on cisco router

A

1) use ip dhcp excluded-address [low-address (high-address)] to identify excluded addresses
2) create DHCP pool using ip dhcp pool pool-name command
3) configure ip addressing parameters

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36
Q

distance vector routing protocols

A

RIP(1&2) IGRP, EIGRP

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37
Q

link state routing protocols

A

OSPF, IS-IS

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38
Q

path vector routing protocols

A

BGP, EGP

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39
Q

IGP & EGP

A

interior gateway protocols used for intra AS routing

exterior gateway protocols route between ASs

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40
Q

what is a distance vector protocol?

A
  • use distance & direction
  • don’t know topology

Works best with

  • flat, simple networks
  • administrators don’t understand link state protocols
  • specific types of networks (hub & spoke) are being implemented
  • worst-case convergence times are not a concern
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41
Q

what are link-state routing protocols

A
  • have complete topology
  • only send updates when topology changes

works best

  • hierarchal networks
  • large networks
  • knowledgeable administrators
  • fast convergence is crucial
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42
Q

how does routing decide between multiple paths to same destination?

A

metric

-metric can viewed with show ip route command

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43
Q

administrative distance

A
  • defines preference of a routing source
  • all routes are prioritized by AD regardless of protocol, static routes, etc.
  • lower value = higher priority
  • can be 0 to 255

verify w/ show ip protocols command

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44
Q

default AD of directly connected & static routes

A

0 and 1 respectively

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45
Q

default EIGRP AD

A

90

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46
Q

default OSPF AD

A

110

47
Q

default RIP AD

A

120

48
Q

RIPv2 metric

A

hop count

49
Q

OSPF metric

A

bandwidth

50
Q

EIGRP metric

A

function of bandwidth and delay(bandwidth+delay)*256

51
Q

preventing routing loops w/distance vector protocols

A
  • define maximum metirc
  • hold down timers
  • split horizon
  • route poisoning or poison reverse
  • triggered updates
  • TTL field in ip header
52
Q

hold-down timers

A

instructs routers to hold any changes that might affect routes for a specific period of time. If a route is identified as down or possibly down any other information for that route containing the same status or worse, is ignored for the hold down period so the network can converge

53
Q

split horizon

A

doesn’t allow advertisement to be sent out the same interface from which they originated

54
Q

route poisoning or poison reverse

A

used to mark route as unreachable in a routing update sent to other routers

55
Q

LSDB & LSA

A

link state database

link state advertisements

56
Q

SPF

A

shortest path first

  • run on LSDF to create SPF tree
  • adds cost associated w/each link between itself
  • lowest cost path is added to routing table
57
Q

how to accomplish inter VLAN routing

A
  • one router interface per vlan
  • router on a stick using trunk link and sub interfaces
  • layer 3 switch
58
Q

feasible successor

A

a neighbor who has a loop free backup path to the same network as the successor by satisfying the feasibility condition

59
Q

standard ACLs

A

filter based on source address

60
Q

extended ACL

A

filters based on source & destination address, protocol, or ports

61
Q

ACL guidelines

A
  • 3 Ps 1 ACL per protocol, per direction, per interface allowed
  • organize from top down, specific to general
  • there is an implicit deny any at end of ACL
  • extended ACLs close to source
  • standard ACL close to destination
62
Q

standard numbered ACLs

A

1-99

1300-1999

63
Q

extended numbered ACLs

A

access-list access-list # {permit | deny} protocol source source-wildcard [operator port] destination destination-wildcard [operator port] [established] [log]

100-199
2000-2699

64
Q

configure named ACLs

A
  • name the ACL ip-access list standard name
  • create ACL
  • apply ACL
65
Q

extended named ACL

A
  • name the ACL ip access-list extended name
  • create ACL
  • apply ACL
66
Q

add comments to ACLs

A

use remark in place of permit or deny in syntax

67
Q

ACL show commands

A

show access-lists
show ip access-list
show ip interface
show running-config

68
Q

standard numbered ACLs

A

1-99

1300-1999

69
Q

extended numbered ACLs

A

access-list access-list # {permit | deny} protocol source source-wildcard [operator port] destination destination-wildcard [operator port] [established] [log]

100-199
2000-2699

70
Q

configure named ACLs

A
  • name the ACL ip-access list standard name
  • create ACL
  • apply ACL
71
Q

extended named ACL

A
  • name the ACL ip access-list extended name
  • create ACL
  • apply ACL
72
Q

add comments to ACLs

A

use remark in place of permit or deny in syntax

73
Q

ACL show commands

A

show access-lists
show ip access-list
show ip interface
show running-config

74
Q

standard numbered ACLs

A

1-99

1300-1999

75
Q

extended numbered ACLs

A

access-list access-list # {permit | deny} protocol source source-wildcard [operator port] destination destination-wildcard [operator port] [established] [log]

100-199
2000-2699

76
Q

configure named ACLs

A
  • name the ACL ip-access list standard name
  • create ACL
  • apply ACL
77
Q

extended named ACL

A
  • name the ACL ip access-list extended name
  • create ACL
  • apply ACL
78
Q

add comments to ACLs

A

use remark in place of permit or deny in syntax

79
Q

ACL show commands

A

show access-lists
show ip access-list
show ip interface
show running-config

80
Q

What is an OSPF router that has interfaces in multiple areas called?

A

Area border router

81
Q

OSPF area 0

A

There must be an area 0

It should be used or the backbone

82
Q

EIGRP IPv4 multicast address

A

224.0.0.10

83
Q

AD in context of EIGRP?

A

Advertised distance.

The total metric along a path to a destination network as advertised by an upstream neighbor

84
Q

How is feasible distance calculated in EIGRP?

A

advertised distance + metric to neighbor

85
Q

What can cause adjacency issues in EIGRP?

A

The interface between the devices is down.
The routers have mismatching EIGRP autonomous systems.
The EIGRP process is not enabled on one of the interfaces that connects the devices.
One of the interfaces that connects the devices is configured as a passive interface.
mismatched K values

86
Q

Issues that prevent routing table from learning appropriate routes

A

Networks are not being advertised on remote routers.
An access list is blocking advertisements of remote networks.
Automatic route summarization is causing confusion in your discontiguous network.

87
Q

EIGRP IPv6 multicast address

A

FF02::A

88
Q

differences in configuring EIGRP for IPv6

A

after configuring the routing process you must issue a no shutdown command in routing configuration mode

there a now network statements. instead you add an interface to routing by issuing a ipv6 eigrp AS# command in interface configuration mode

89
Q

What are OSPF dbd packets?

A

Database Description packets contain LSA headers that help routers build the link state database.

90
Q

What are OSPF LSR packets?

A

Once DBD packets are exchanged, each router checks the LSA Headers against its own database. If it it does not have current information for any LSA, it generates an LSR packets and sends it to its neighbor to request updated LSAs.

91
Q

What are OSPF LSU packets?

A

LSU packets contains a list of LSAs that are to be updated. This packet is often used in flooding.

92
Q

What are OSPF LSAck packets

A

LSAck packets help to ensure reliable transmission of LSAs. Each LSA is explicitly acknowledged.

93
Q

The default OSPF costs are based on a reference of 100mbps. What are the 3 options to adjust this for faster links?

A

Set the reference bandwidth globally
manually set the interface cost on specific interfaces
manually configure the reference bandwidth per interface

94
Q

What process is used for OSPF routers to exchange information

A

The routers exchange one or more DBD packets. A DBD includes information about the LSA entry header that appears in the LSDB of the router. Each LSA entry header includes information about the link-state type, the address of the advertising router, the cost of the link, and the sequence number. The router uses the sequence number to determine the “newness” of the received link-state information.
When the router receives the DBD, it acknowledges the receipt of the DBD that is using the LSAck packet.
Routers compare the information that they receive with the information that they have. If the received DBD has a more up-to-date link-state entry, the router sends an LSR to the other router to request the updated link-state entry.
The other router responds with complete information about the requested entry in an LSU packet. The other router adds the new link-state entries to its LSDB.
When the router receives an LSU, it sends an LSAck.

95
Q

OSPF backbone area, or area 0

A

The primary function of this OSPF area is to quickly and efficiently move IP packets. Backbone areas interconnect with other OSPF area types. The OSPF hierarchical area structure requires that all areas connect directly to the backbone area. In the figure, links between Area 1 and Area 2 routers are not allowed. Generally, end users are not found within a backbone area, which is also known as OSPF Area 0.

96
Q

Normal or non backbone OSPF area

A

The primary function of this OSPF area is to connect users and resources. Normal areas are usually set up according to functional or geographical groupings. By default, a normal area does not allow traffic from another area to use its links to reach other areas. All traffic from other areas must cross a transit area such as Area 0.

97
Q

What does an OSPF autonomous system consist of ?

A

all of the OSPF areas and routers that are running the OSPF routing protocol.

98
Q

What are OSPF internal routers?

A

non backbone routers that have all interfaces in a single area

99
Q

What are OSPF area border routers?

A

routers that connect nonbackbone areas to the backbone area

100
Q

What functions does an OSPF area border router perform?

A

It separates LSA flooding zones.
It becomes the primary point for area address summarization.
It functions regularly as the source for default routes.
It maintains the LSDB for each area with which it is connected.

101
Q

What is the ideal design for how many areas an ABR connects to?

A

The ideal design is to have each ABR connected to two areas only, the backbone and another area, with three areas being the upper limit.

102
Q

What is an autonomous system boundary router ASBR?

A

An ABR located between an OSPF autonomous system and a non-OSPF network. ASBRs run both OSPF and another routing protocol, such as RIP. ASBRs must reside in a nonstub OSPF area.

103
Q

Type 1 LSA

A

router LSA

Every router generates router link advertisements for each area to which it belongs. Router link advertisements describe the state of the router links to the area and are flooded only within this particular area.

104
Q

Type 2 LSA

A

network LSA

Network LSAs are generated only by designated routers and describe the set of routers attached to a particular nonbroadcast multiaccess (NBMA) or broadcast network. The purpose of the network LSA is to ensure that only one LSA is generated for the NBMA or broadcast network (as opposed to one from each attached router). This is a form of internal OSPF summarization.

105
Q

Type 3 LSA

A

summary LSA

Summary LSAs are generated by area border routers (ABRs) and describe inter-area routes to various networks. Specifically, Type 3 LSAs describe networks that are within the OSPF autonomous system but outside of the particular OSPF area that is receiving the LSA.

106
Q

Type 4 LSA

A

ASBR summary LSA

Each summary LSA describes a route to a destination outside the OSPF area yet still inside the autonomous system (that is, an inter-area route). the Type 4 summary LSAs describe routes to autonomous system boundary routers (ASBRs) and are also generated by ABRs.

107
Q

Type 5 LSA

A

Autonomous system LSA

Type 5 LSAs are generated by the ASBRs. These LSAs describe routes to destinations that are external to the AS. Type 5 LSAs are flooded everywhere, with the exception of stub areas.

108
Q

max number of routers that should participate in an OSPF area

A

50

109
Q

What are the major components of OSPF troubleshooting?

A

OSPF neighbor adjacencies
OSPF routing table
OSPF path selection

110
Q

Key OSPFv3 Characteristics

A

As in OSPFv2, each OSPF router is uniquely identified by its RID, a 32-bit number that is based on an IPv4 address of the router. If no IPv4 address is configured, you will be prompted to configure it using the router-id command.
Adjacencies and next-hop attributes use IPv6 link-local addresses.
IPv6 is used for transport of LSAs.
OSPFv3 is enabled per link instead per network as in OSPFv2.
OSPFv3 communicates with its peers using IPv6 multicast addresses.

111
Q

OSPFv3 multicast addresses

A

FF02::5 for all OSPF routers
FF02::6 for the OSPF DR and OSPF BDR.

112
Q

command to enable OSPFv3 on an interface

A

ipv6 ospf process-id area area-id

113
Q

show command to get general OSPFv3 info

A

show ipv6 ospf

CCNA (12 decks)

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