Configuring a Default Route on a Router 71By default, a static route is always used rather than a routing protocol.. 72 Configuration Example: Static RoutesVerifying Static Routes To dis
Trang 1Configuring a Default Route on a Router 71
By default, a static route is always used rather than a routing protocol By adding an AD
number to your ip route statement, however, you can effectively create a backup route
to your routing protocol If your network is using EIGRP, and you need a backup route, add
a static route with an AD greater than 90 EIGRP will be used because its AD is better (lower) than the static route If EIGRP goes down, however, the static route will be used in
its place This is known as a floating static route.
If a static route refers to an exit interface rather than a next-hop address, the destination is considered to be directly connected and is therefore given an AD of 0 rather than 1.
Configuring a Default Route on a Router
Exterior Border Gateway Protocol (eBGP) 20
Trang 272 Configuration Example: Static Routes
Verifying Static Routes
To display the contents of the IP routing table, enter the following command:
Router#sshshohoowww iipip p rrrooouututete
NOTE: The codes to the left of the routes in the table tell you from where the
router learned the routes A static route is described by the letter S.
Configuration Example: Static Routes
Figure 7-1 illustrates the network topology for the configuration that follows, which shows how to configure static routes using the commands covered in this chapter.
Figure 7-6 Network Topology for Static Route Configuration
NOTE: The host names, passwords, and interfaces have all been configured using the commands shown in the configuration example in Chapter 6,
“Configuring a Single Cisco Router.”
Boston Router
Boston>eenennaaabbbllele Moves to privileged mode
Boston#ccocoonnnfffiigiguguurrree e ttteeerrrmmimiinnnaaall Moves to global
configuration mode
s0/0/1 DCE
172.16.40.2
s0/0/0 172.16.40.1
Network 172.16.50.0/24
fa0/0
172.16.50.50 Bangor
Network 172.16.10.0/24
s0/0/1 DCE
Trang 3Configuration Example: Static Routes 73
2
255555.5.2.22555555 2.22555555 0.0 0 11177722.2 111666 2.22000 22
Configures a static route using the next-hop addressBoston(config)#iipip p rrrooouututteee 117172722 11166.6 555000 0.00
2
255555.5.2.22555555 2.22555555 0.0 0 11177722.2 111666 2.22000 22
Configures a static route using the next-hop addressBoston(config)#eexexixiitt Moves to privileged mode
Boston#ccocoopppyyy rruruunnnnninininnggg -ccocoonnnfffiigig g ssstttaararrtttuuupp-p-c-ccooonnnffifiigg Saves the configuration to
NVRAM
Buffalo>eeennnaaabblbllee Moves to privileged mode
Buffalo#cccooonnnffifiiggguuurrere e ttteeerrmrmmiiinnnaalal Moves to global
configuration modeBuffalo(config)#iipipp rrroououuttteee 117177222 116166 11100.0 000
2
255555.5.2.22555555 2.22555555 0.0 0 ssseeerririiaaalll 000///000//1/1
Configures a static route using the exit interfaceBuffalo(config)#iipipp rrroououuttteee 117177222 116166 55500.0 000
2
255555.5.2.22555555 2.22555555 0.0 0 ssseeerririiaaalll 000///000//0/0
Configures a static route using the exit interfaceBuffalo(config)#eexexxiiitt Moves to privileged mode
Buffalo#cccooopppyy y rrruuunnnnniniinnnggg c-ccooonnnffifigigg sssttataarrrtttuupup-p cccooonnfnffiiigg Saves the configuration to
NVRAM
Bangor>eenennaaabbbllele Moves to privileged mode
Bangor#ccocoonnnfffiigiguguurrree e ttteeerrrmmimiinnnaaall Moves to global
configuration modeBangor(config)#iipip p rroroouuutttee e 00.0.0.00 000 0.0 0 00.0 000 00.0.0.00 ssseeerrriiaialall
0
0///00/0/1/1
Configures a static route using the default routeBangor(config)#eexexixiitt Moves to privileged mode
Bangor#ccocoopppyyy rruruunnnnninininnggg -ccocoonnnfffiigig g ssstttaararrtttuuupp-p-c-ccooonnnffifiigg Saves the configuration to
NVRAM
Trang 4This page intentionally left blank
Trang 5CHAPTER 8
RIP
This chapter provides information and commands concerning the following topics:
• The ip classless command
• RIP routing: mandatory commands
• RIP routing: optional commands
• Troubleshooting RIP issues
• Configuration example: RIPv2 routing
The ip classless Command
NOTE: A supernet route is a route that covers a range of subnets with a single entry
NOTE: The ip classless command is enabled by default in Cisco IOS
Soft-ware Release 11.3 and later
RIP Routing: Mandatory Commands
Router(config)#iipipp cccllalaassssssllelesessss Instructs Cisco IOS Software
to forward packets destined for
an unknown subnet to the best supernet route
Router(config)#nnonoo iiipp p ccclllaasasssssllleeesssss Turns off the ip classless
command
Router(config)#rroroouuuttteererr rrriipip Enables RIP as a routing
protocol.
Router(config-router)#nnneetetwtwwooorrrkk k w.x.y.z w.x.y.z is the network number
of the directly connected
network you want to advertise.
Trang 676 RIP Routing: Optional Commands
NOTE: You need to advertise only the classful network number, not a subnet:Router(config-router)#nnneeettwtwowoorrrkk k 111777222 1.11666 00.0.0.0
not
Router(config-router)#nnneeettwtwowoorrrkk k 111777222 1.11666 11010.0 00
If you advertise a subnet, you will not receive an error message, because the router will automatically convert the subnet to the classful network address
RIP Routing: Optional Commands
Router(config)#nnono o rrrooouututteeerrr rririipp Turns off the RIP routing
process.
Router(config-router)#nnnooo nneneetttwwowororrkkk w.x.y.z Removes network w.x.y.z
from the RIP routing process.Router(config-router)#vvveeerrsrsisiiooonn n 22 RIP will now send and
receive RIPv2 packets globally.
Router(config-router)#vvveeerrsrsisiiooonn n 11 RIP will now send and
receive RIPv1 packets only.Router(config-if)#iiippp rrriiippp sseseennnddd vvveeerrrssisiiooonnn 11 The interface will send only
RIPv1 packets.
Router(config-if)#iiippp rrriiippp sseseennnddd vvveeerrrssisiiooonnn 22 The interface will send only
RIPv2 packets.
Router(config-if)#iiippp rrriiippp sseseennnddd vvveeerrrssisiiooonnn 11 1 22 The interface will send both
RIPv1 and RIPv2 packets.Router(config-if)#iiippp rrriiippp rrereeccceeeiivivveee vveveerrrsssiioiononn 11 The interface will receive
only RIPv1 packets.Router(config-if)#iiippp rrriiippp rrereeccceeeiivivveee vveveerrrsssiioiononn 22 The interface will receive
only RIPv2 packets.Router(config-if)#iiippp rrriiippp rrereeccceeeiivivveee vveveerrrsssiioiononn 111 22 The interface will receive
both RIPv1 and RIPv2 packets.
Router(config-router)#nnnooo aauauutttoo-o-s-ssuuummmmmamaarrryy RIPv2 summarizes networks
at the classful boundary This command turns auto- summarization off.
Trang 7Troubleshooting RIP Issues 77
Troubleshooting RIP Issues
Router(config-router)#nnneeeiigighghhbbbooror a.b.c.dr Defines a specific neighbor
with which to exchange information.
Router(config-router)#nnnooo iipipp sspsplplliiittt h-hhooorrriizizozoonn Turns off split horizon (on
Changes timers in RIP:
30 = Update timer (in seconds)
90 = Invalid timer (in seconds)
180 = Hold-down timer (in seconds)
270 = Flush timer (in seconds)
360 = Sleep time (in milliseconds)Router(config-router)#mmmaaaxxiximimmuuumm-m-p-ppaaattthhshss x Limits the number of paths
for load balancing to x (4 =
default, 6 = maximum).Router(config-router)#dddeeeffafauauullltt-t-i-iinnnfffoororrmmmaaattitioioonnn
database
Trang 878 Configuration Example: RIPv2 Routing
Configuration Example: RIPv2 Routing
Figure 8-1 illustrates the network topology for the configuration that follows, which shows how to configure RIPv2 using the commands covered in this chapter.
Figure 8-7 Network Topology for RIPv2 Routing Configuration
NOTE: The host name, password, and interfaces have all been configured as per the configuration example in Chapter 6, “Configuring a Single Cisco Router.”
Cancun Router
Cancun>eenennaaabbbllele Moves to privileged mode
Cancun#ccocoonnnfffiigiguguurrree e ttteeerrrmmimiinnnaaall Moves to global configuration
modeCancun(config)#rrorououuttteeerr r rrriiipp Enables RIP routing
Cancun(config-router)#vvveeerrsrsisiiooonn n 22 Enables RIPv2
Cancun(config-router)#nnneeettwtwowoorrrkk k 111777222 1.11666 00.0.0.0 Advertises directly connected
networks (classful address only)Cancun(config-router)#nnnooo aauauutttoo-o-s-ssuuummmmmamaarrryy Turns off auto-summarization
s0/0/1 DCE
172.16.40.2
s0/0/0 172.16.40.1
Trang 9Configuration Example: RIPv2 Routing 79
Acapulco Router
Mazatlan Router
Cancun(config-router)#eeexxxiitit Returns to global configuration
modeCancun(config)#eexexixiitt Returns to privileged mode
Cancun#ccocoopppyyy rruruunnn sststtaaarrrtt Saves the configuration to
NVRAM
Acapulco>eeennnaababblllee Moves to privileged mode
Acapulco#cccooonnfnffiiiggguurureree ttteererrmmmiiinnanalal Moves to global configuration
modeAcapulco(config)#rrrooouuutteteerrr rriripip Enables RIP routing
Acapulco(config-router)#vvevererrsssiioiononn 22 Enables RIPv2
Acapulco(config-router)#eexexixiitt Moves to global configuration
modeAcapulco(config)#eeexxxiiitt Returns to privileged mode
Mazatlan>eeennnaababblllee Moves to privileged mode
Mazatlan#cccooonnfnffiiiggguurureree ttteererrmmmiiinnanalal Moves to global configuration
modeMazatlan(config)#rrrooouuutteteerrr rriripip Enables RIP routing
Mazatlan(config-router)#vvevererrsssiioiononn 22 Enables RIPv2
Trang 1080 Configuration Example: RIPv2 Routing
Mazatlan(config-router)#nnono o aaauututotoo -sssuumummmmmaaarryry Turns off auto-summarization
Mazatlan(config-router)#eexexixiitt Moves to global configuration
modeMazatlan(config)#eeexxxiiitt Returns to privileged mode
Trang 11CHAPTER 9
EIGRP
This chapter provides information and commands concerning the following topics:
• Configuring Enhanced Interior Gateway Routing Protocol (EIGRP)
• Configuration example: EIGRP
Configuring Enhanced Interior Gateway Routing Protocol (EIGRP)
Router(config)#rroroouuuttteererr eeeiigigrgrrppp 11010000 Turns on the EIGRP process.
100 is the autonomous system number, which can be a number between 1 and 65,535.
All routers in the same autonomous system must use the same autonomous system number.
Router(config-router)#nnneetetwtwwooorrrkk k 111000 0.0.0 000 0.0 Specifies which network to
advertise in EIGRP.
Router(config-if)#bbbaananndddwwwiididtdtthhh x Sets the bandwidth of this
interface to x kilobits to allow
EIGRP to make a better metric calculation.
TIP: The bandwidth
command is used for metric calculations only It does not change interface
Trang 1282 EIGRP Auto-Summarization
NOTE: tos is a reference to the original Interior Gateway Routing Protocol
(IGRP) intention to have IGRP perform type-of-service routing Because this
was never adopted into practice, the tos field in this command is always
set to zero (0)
NOTE: With default settings in place, the metric of EIGRP is reduced to the slowest bandwidth plus the sum of all the delays of the exit interfaces from the local router to the destination network
TIP: For two routers to form a neighbor relationship in EIGRP, the k values must
match
CAUTION: Unless you are very familiar with what is occurring in your network,
it is recommended that you do not change the k values.
mask range of the network
statement A network mask can also be used here.
Router(config-router)#mmmeeettrtririiccc wweweeiiiggghhthtstss tos
k1 k2 k3 k4 k5
Changes the default k values
used in metric calculation
These are the default values: tos=0, k1=1, k2=0, k3=1, k4=0, k5=0
Router(config-router)#aaauuuttoto-o sssuumummmmmaaarrryy Enables auto-summarization for the
EIGRP process.
NOTE: The default behavior of
auto-summarized changed from enabled to disabled was introduced in Cisco IOS Software Release 12.2(8)T.
Trang 13Load Balancing: variance 83
CAUTION: EIGRP automatically summarizes networks at the classful boundary
A poorly designed network with discontiguous subnets could have problems with connectivity if the summarization feature is left on For instance, you could have two routers advertise the same network—172.16.0.0/16—when in fact they wanted to advertise two different networks—172.16.10.0/24 and 172.16.20.0/24
Recommended practice is that you turn off automatic summarization if
necessary, use the ip summary-address command, and summarize manually
what you need to
Load Balancing: variance
NOTE: The behavior of the summary command is disabled by
auto-default, beginning in Cisco IOS Software Release 12.2(8)T This means that Cisco IOS Software will now send subprefix routing information across classful network boundaries.
75 is assigned to this summary route.
NOTE: The administrative-distance
argument is optional in this command Without it, an administrative distance of
5 is automatically applied to the summary route.
Router(config)#rrorououuttteeerr r eeeiiiggrgrprpp 11100000 Creates routing process 100
Router(config-router)#vvvaaarririaiaannnccece ne Instructs the router to include routes
with a metric less than or equal to n
times the minimum metric route for that
destination, where n is the number
specified by the variance command
Trang 1484 Authentication
NOTE: If a path is not a feasible successor, it is not used in load balancing
NOTE: EIGRP supports up to six unequal-cost paths
Bandwidth Use
NOTE: By default, EIGRP is set to use only up to 50 percent of the bandwidth of
an interface to exchange routing information Values greater than 100 percent can be configured This configuration option might prove useful if the bandwidth
is set artificially low for other reasons, such as manipulation of the routing metric
or to accommodate an oversubscribed multipoint Frame Relay configuration
NOTE: The ip bandwidth-percent command relies on the value set by the bandwidth command.
Authentication
Router(config)#iinintntteeerrrffafaaccceee sseseerrriiiaalall 000//0/0 Enters interface configuration mode.
Router(config-if)#bbbaaanndnddwwwiiiddtdththh 22255656 Sets the bandwidth of this interface
to 256 kilobits to allow EIGRP to make a better metric calculation.Router(config-if)#iiippp bbabaannndddwwiwididdttthhh p-ppeeerrrccecenennttt
e
eiiiggrgrprpp 55500 0 11100000
Configures the percentage of bandwidth that may be used by EIGRP on an interface.
50 is the EIGRP autonomous system number.
100 is the percentage value.
Trang 15Authentication 85
NOTE: For the start time and the end time to have relevance, ensure that the router knows the correct time Recommended practice dictates that you run Network Time Protocol (NTP) or some other time-synchronization method if you intend to set lifetimes on keys
Router(config)#kkekeyeyy ccchhahaaiiinnn rroroommmeeeoo Identifies a key chain The name must
match the name configured in interface configuration mode above
Router(config-keychain)#kkekeyeyy 11 Identifies the key number.
NOTE: The range of keys is from
0 to 2147483647 The key identification numbers do not need to be consecutive
At least 1 key must be defined on a key chain.
Router(config-keychain-key)#kkekeyeyy-
-s
stttrririninnggg sshshhaaakkkeesespsppeeeaaarrere
Identifies the key string.
NOTE: The string can contain from
1 to 80 uppercase and lowercase alphanumeric characters, except that the first character cannot be a number.Router(config-keychain-
NOTE: The default start time and the
earliest acceptable date is January 1,
1993 The default end time is an infinite period.
NOTE: The default start time and the
earliest acceptable date is January 1,
1993 The default end time is an infinite period.