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© 2008 Cisco Systems, Inc. Al l r ights reserved. Cisco ConfidentialPresentation_ID

Cha!ter "# Inter$%&A'

(o)ting

Routing & Switching

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Presentation_ID 2© 2008 Cisco Systems, Inc. Al l r ights reserved. Cisco Confidential

Chapter 5

". Inter$%&A' (o)ting Config)ration

".2 *ro)+leshooting Inter$%&A' (o)ting

". &ayer S-itching

". S)mmary

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Presentation_ID © 2008 Cisco Systems, Inc. Al l r ights reserved. Cisco Confidential

Chapter 5: Objectives

Descri+e the three !rimary o!tions for ena+ling inter$%&A' ro)ting.

Config)re legacy inter$%&A' ro)ting.

Config)re ro)ter$on$a$stic/ inter$%&A' ro)ting.

*ro)+leshoot common inter$%&A' config)ration iss)es.

*ro)+leshoot common IP addressing iss)es in an inter$%&A'$ro)tedenvironment.

Config)re inter$%&A' ro)ting )sing &ayer s-itching.

*ro)+leshoot inter$%&A' ro)ting in a &ayer $s-itched environment.

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". Inter$%&A' (o)ting

Config)ration

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Inter-VLAN Routing Operation

hat is Inter-VLAN routing!

&ayer 2 s-itches cannot for-ard traffic +et-een %&A's -itho)t theassistance of a ro)ter.

Inter$%&A' ro)ting is a !rocess for for-arding net-or/ traffic fromone %&A' to another, )sing a ro)ter.

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Legac" Inter-VLAN Routing

In the !ast#

Act)al ro)ters -ere )sed to ro)te +et-een %&A's.

1ach %&A' -as connected to a different !hysical ro)ter interface.

Pac/ets -o)ld arrive on the ro)ter thro)gh one thro)gh interface,

+e ro)ted and leave thro)gh another. eca)se the ro)ter interfaces -ere connected to %&A's and had

IP addresses from that s!ecific %&A', ro)ting +et-een %&A's-as achieved.

&arge net-or/s -ith large n)m+er of %&A's re3)ired many ro)ter

interfaces.

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Router-on-a-Stic# Inter-VLAN Routing

*he ro)ter$on$a$stic/ a!!roach )ses a different !ath to ro)te+et-een %&A's.

5ne of the ro)ter6s !hysical interfaces is config)red as a 802.7tr)n/ !ort so it can )nderstand %&A' tags.

&ogical s)+interfaces are created one s)+interface !er %&A'.

1ach s)+interface is config)red -ith an IP address from the %&A' itre!resents.

%&A' mem+ers 9hosts: are config)red to )se the s)+interfaceaddress as a defa)lt gate-ay.

5nly one of the ro)ter6s !hysical interface is )sed.

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$u%ti%a"er Switch Inter-VLAN Routing

;)ltilayer s-itches can !erform &ayer 2 and &ayer f)nctions,re!lacing the need for dedicated ro)ters.

;)ltilayer s-itches s)!!ort dynamic ro)ting and inter$%&A' ro)ting.

*he m)ltilayer s-itch m)st have IP ro)ting ena+led.

A s-itch virt)al interface 9S%I: e)st as a ro)ter ro)tes +et-een its interfaces.

?ith a m)ltilayer s-itch, traffic is ro)ted internal to the s-itch device.

*his ro)ting !rocess is a s)ita+le and scala+le sol)tion.

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Conigure Legac" Inter-VLAN Routing

'reparation

&egacy inter$%&A' ro)ting re3)ires ro)ters to have m)lti!le!hysical interfaces.

1ach one of the ro)ter6s !hysical interfaces is connected to a)ni3)e %&A'.

1ach interface is also config)red -ith an IP address for the s)+netassociated -ith the !artic)lar %&A'.

'et-or/ devices )se the ro)ter as a gate-ay to access thedevices connected to the other %&A's.

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'reparation (cont)*

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Switch Coniguration

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Router Interace Coniguration

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Conigure Router-on-a-Stic#

'reparation

An alternative to legacy inter$%&A' ro)ting is to )se %&A' tr)n/ingand s)+interfaces.

%&A' tr)n/ing allo-s a single !hysical ro)ter interface to ro)tetraffic for m)lti!le %&A's.

*he !hysical interface of the ro)ter m)st +e connected to a tr)n/lin/ on the ad>acent s-itch.

5n the ro)ter, s)+interfaces are created for each )ni3)e %&A'.

1ach s)+interface is assigned an IP address s!ecific to its s)+netor %&A' and is also config)red to tag frames for that %&A'.

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Switch Coniguration

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Router Subinterace Coniguration

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Veri"ing Subinteraces

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Veri"ing Subinteraces (cont)*

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Access to devices on remote %&A's can +e tested )singthe ping command.

*he ping command sends an IC;P echo re3)est to thedestination address.

?hen a host receives an IC;P echo re3)est, it res!onds -ith anIC;P echo re!ly.

*racert is a )sef)l )tility for confirming the ro)ted !ath ta/en+et-een t-o devices.


Veri"ing Routing

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.2 *ro)+leshoot Inter$

%&A' (o)ting

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?hen )sing the legacy ro)ting model, ens)re that the s-itch !ortsconnect to the ro)ter interfaces and are config)red -ith the correct%&A's.

=se the switchport access vlan [appropriate vlan#]command to correct any erroneo)s %&A' !ort assignment.

1ns)re that the ro)ter is connected to the correct s-itch !ort.

?hen )sing ro)ter$on$a$stic/, ens)re that the s-itch !ortconnected to the ro)ter is config)red as a tr)n/ lin/.

=se the switchport mode trunk command to ma/e the

s-itch !ort a tr)n/.

Inter-VLAN Coniguration Issues

Switch 'ort Issues

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Veri" Switch Coniguration

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?ith ro)ter$on$a$stic/ config)rations, a common !ro+lem isassigning the -rong %&A' ID to the s)+interface.

*he show interface command can hel! detect this !ro+lem.

If this is the case, )se the encapsulation dot1q

interface command to fi< the !ro+lem.


Veri" Router Coniguration

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Veri" Router Coniguration (cont)*

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?hen )sing legacy inter$%&A' ro)ting, ens)re that the ro)ter hasthe correct IP address and mas/ on the interfaces connecting tothe s-itch.

1ns)re that the net-or/ devices are config)red -ith the correct IPaddress and mas/.

In the ro)ter, )se the ip address command to fi< any erroneo)sIP assignments.

In the PCs, refer to the installed o!erating system doc)mentationto !ro!erly change IP information.

I' A++ressing Issues

,rrors with I' A++ress an+ Subnet $as#s

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Presentation_ID 2"© 2008 Cisco Systems, Inc. Al l r ights reserved. Cisco Confidential

=se the show ip interface command to verify if the correctIP address is config)red in the ro)ter.

=se the show running-config -hen tro)+leshooting ro)ter$related !ro+lems.

?hen tro)+leshooting addressing iss)es, ens)re that thes)+interface is config)red -ith the correct address for that %&A'.

S)+interface IDs are often config)red to match the %&A' n)m+er,-hich ma/es it easier to manage inter$%&A' config)ration, +)t thisis not a re3)irement.

I' A++ressing Issues

Veri"ing I' A++ress an+ Subnet $as#

Coniguration Issues

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© 2008 Cisco Systems, Inc. Al l r ights reserved. Cisco ConfidentialPresentation_ID 2

". &ayer S-itching

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&ayer s-itches )s)ally have !ac/et$s-itching thro)gh!)ts in themillions of !ac/ets !er second 9!!s:.

All Catalyst m)ltilayer s-itches s)!!ort the follo-ing ty!es of &ayer interfaces#

(o)ted !ort S-itch virt)al interface 9S%I:

Bigh$!erformance s-itches, s)ch as the Catalyst "00 and Catalyst"00, are a+le to !erform most of the ro)ter6s f)nctions.

Several models of Catalyst s-itches re3)ire enhanced soft-are fors!ecific ro)ting !rotocol feat)res.

La"er Switching Operation an+ Coniguration

Intro+uction to La"er Switching

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*oday6s ro)ting has +ecome faster and chea!er and can +e!erformed at hard-are s!eed.

(o)ting can +e transferred to core and distri+)tion devices -ithlittle to no im!act on net-or/ !erformance.

;any )sers are in se!arate %&A's, and each %&A' is )s)ally ase!arate s)+net. *his im!lies that each distri+)tion s-itch m)sthave IP addresses matching each access s-itch %&A'.

&ayer 9ro)ted: !orts are normally im!lemented +et-een thedistri+)tion and the core layer. *his model is less de!endent on

s!anning tree, +eca)se there are no loo!s in the &ayer 2 !ortion ofthe to!ology.


Inter-VLAN Routing with Switch Virtua% Interaces

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Presentation_ID 2@© 2008 Cisco Systems, Inc. Al l r ights reserved. Cisco Confidential

y defa)lt, an S%I is created for the defa)lt %&A' 9%&A' :. *hisallo-s for remote s-itch administration.

Any additional S%Is m)st +e created +y the administrator.

S%Is are created the first time the %&A' interface config)ration

mode is entered for a !artic)lar %&A' S%I. 1nter the interface vlan 10 command to create an S%I

named %&A' 0.

*he %&A' n)m+er )sed corres!onds to the %&A' tag associated-ith data frames on an 802.7 enca!s)lated tr)n/.

?hen the S%I is created, ens)re that the s!ecific %&A' is !resent inthe %&A' data+ase.


Inter-VLAN Routing with SVIs (Cont)*

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S%Is advantages incl)de#

;)ch faster than ro)ter$on$a$stic/, +eca)se everything is

hard-are$s-itched and ro)ted.

'o need for e

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A ro)ted !ort is a !hysical !ort that acts similarly to an interface on aro)ter.

(o)ted !orts are not associated -ith any %&A's.

&ayer 2 !rotocols, s)ch as S*P, do not f)nction on a ro)ted interface.

(o)ted !orts on a Cisco I5S s-itch do not s)!!ort s)+interfaces. *o config)re ro)ted !orts, )se the no switchport interface

config)ration mode command.

Note# (o)ted !orts are not s)!!orted on Catalyst 2@0 Seriess-itches.


Inter-VLAN Routing with Route+ 'orts

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*he Cisco S-itch Data+ase ;anager 9SD;: !rovides m)lti!letem!lates for the Cisco Catalyst 2@0 s-itch.

*he SD; lanbase-routing tem!late can +e ena+led to allo- thes-itch to ro)te +et-een %&A's and to s)!!ort static ro)ting.

=se the show sdm prefer command to verify -hich tem!late isin )se.

*he SD; tem!late can +e changed in glo+al config)ration mode-ith the sdm prefer command.


Coniguring Static Routes on a Cata%"st ./01

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*o tro)+leshoot &ayer s-itching iss)es, verify the follo-ing foracc)racy#

VLANs

%&A's m)st +e defined across all the s-itches.

%&A's m)st +e ena+led on the tr)n/ !orts. Ports m)st +e in the right %&A's.

SVIs

S%Is m)st have the correct IP address or s)+net mas/.

S%Is m)st +e )!. S%Is m)st match -ith the %&A' n)m+er.

2roub%eshooting La"er Switching

La"er Switch Coniguration Issues

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*o tro)+leshoot &ayer s-itching iss)es, verify the follo-ing for

acc)racy#

Routing

(o)ting m)st +e ena+led.

1ach interface or net-or/ sho)ld +e added to the ro)ting!rotocol.

3osts

Bosts m)st have the correct IP address or s)+net mas/.

Bosts m)st have a defa)lt gate-ay associated -ith an S%I orro)ted !ort.

2roub%eshooting La"er Switching

La"er Switching Coniguration Issues (Cont)*

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Presentation_ID "© 2008 Cisco Systems, Inc. Al l r ights reserved. Cisco Confidential

Chapter 5: Su44ar"

*his cha!ter descri+ed and e

Inter$%&A' ro)ting, the !rocess of ro)ting traffic +et-een different%&A's, )sing either a dedicated ro)ter or a m)ltilayer s-itch

&egacy, ro)ter$on$a$stic/, and m)ltilayer s-itch inter$%&A' ro)ting

&ayer s-itching, S%Is, and ro)ted !orts

*ro)+leshooting inter$%&A' ro)ting -ith a ro)ter or a &ayer s-itch

Common errors involving %&A', tr)n/, &ayer interface, and IPaddress config)rations

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Chapter 5: Su44ar"

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