Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide

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Chapter 4

Configuring PPP over ATM with NAT

Configure the ATM WAN Interface

Configure the ATM WAN Interface

Perform these steps to configure the ATM interface, beginning in global configuration mode.

Command

Purpose

Step 1

interface

type number

Example:

Router(config)#

interface atm 0

Router(config-if)#

Enters interface configuration mode for the ATM

interface (labeled ADSLoPOTS or G.SHDSL on

the back of your router).

Note

This interface was initially configured

during basic router configuration. See the

“Configure WAN Interfaces” section on

page 1-6

.

Step 2

pvc

vpi

/

vci

Example:

Router(config-if)#

pvc 8/35

Router(config-if-atm-vc)#

Creates an ATM PVC for each end node (up to ten)

with which the router communicates. Enters ATM

virtual circuit configuration mode.

When a PVC is defined, AAL5SNAP

encapsulation is defined by default. Use the

encapsulation

command to change this, as shown

in

Step 3

. The VPI and VCI arguments cannot be

simultaneously specified as zero; if one is 0, the

other cannot be 0.

For details about this command and additional

parameters that can be set, see the

Cisco IOS

Wide-Area Networking Command Reference

.

Step 3

encapsulation

{

aal5auto

|

aal5autoppp

virtual-template

number

[

group

group-name

] |

aal5ciscoppp virtual-template

number

|

aal5mux

protocol

|

aal5nlpid

|

aal5snap

}

Example:

Router(config-if-atm-vc)#

encapsulation

aal5mux ppp dialer

Router(config-if-atm-vc)#

Specifies the encapsulation type for the PVC and

points back to the dialer interface.

For details about this command and additional

parameters that can be set, see the

Cisco IOS

Wide-Area Networking Command Reference

.

Step 4

dialer pool-member

number

Example:

Router(config-if-atm-vc)#

dialer

pool-member 1

Router(config-if-atm-vc)#

Specifies the ATM interface as a member of a

dialer profile dialing pool. The pool number must

be in the range of 1–255.

Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide

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Chapter 4

Configuring PPP over ATM with NAT

Configure DSL Signaling Protocol

Configure DSL Signaling Protocol

DSL signaling must be configured on the ATM interface for connection to your ISP. The Cisco 857 and

Cisco 877 routers support ADSL signaling over POTS, the Cisco 876 supports ADSL signaling over

ISDN, and the Cisco 878 supports SHDSL signaling. Based on the router you are configuring, see one

of the following sections to configure the appropriate DSL signaling protocol.

•

Configuring ADSL

•

Configuring SHDSL

Configuring ADSL

The default configuration for ADSL signaling is shown in

Table 4-1

.

Table 4-1

Default ADSL Configuration

Attribute

Description

Default Value

Operating mode

Specifies the operating mode of the digital subscriber line

(DSL) for an ATM interface.

•

ADSL over POTS—ANSI or ITU full rate, or

automatic selection.

•

ADSL over ISDN—ITU full rate, ETSI, or

automatic selection.

Auto

Loss of margin

Specifies the number of times a loss of margin may occur.

—

Training log

Toggles between enabling the training log and disabling the

training log.

Disabled

Step 5

no shutdown

Example:

Router(config-if-atm-vc)#

no shutdown

Router(config-if)#

Enables interface and configuration changes just

made to the ATM interface.

Step 6

exit

Example:

Router(config-if)#

exit

Router(config)#

Exits configuration mode for the ATM interface.

Command

Purpose

Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide

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Chapter 4

Configuring PPP over ATM with NAT

Configure DSL Signaling Protocol

If you wish to change any of these settings, use one of the following commands in global configuration

mode.

•

dsl operating-mode

(from the ATM interface configuration mode)

•

dsl lom

integer

•

dsl enable-training-log

See the

Cisco IOS Wide-Area Networking Command Reference

for details of these commands.

Verify the Configuration

You can verify that the configuration is set the way you want by using the

show dsl interface atm

command from privileged EXEC mode.

Configuring SHDSL

Complete the following steps to configure the DSL controller in your router to use SHDSL signaling,

beginning in global configuration mode.

Command

Purpose

Step 1

controller dsl

port

Example:

Router(config)#

controller dsl 0

Router(config-controller)#

Enters the configuration mode for the DSL

controller.

Step 2

line-term

{

co

|

cpe

}

Example:

Router(config-controller)#

line-term co

Router(config-controller)#

Specifies if the DSL line is terminated at a central

office (CO) or at customer premises equipment

(CPE).

Step 3

exit

Example:

Router(config-controller)#

exit

Router(config)#

Exits controller configuration mode, returning to

global configuration mode.

Step 4

mode

protocol

Example:

Router(config)#

mode atm

Router(config-controller)#

Specifies the mode of the DSL controller and

enters controller configuration mode.

Step 5

line-mode

{

4-wire

|

2-wire

}

Example:

Router(config-controller)#

line-mode 4-wire

Router(config-controller)#

Specifies whether this DSL connection is

operating in 2-wire or 4-wire mode.

Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide

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Chapter 4

Configuring PPP over ATM with NAT

Configure DSL Signaling Protocol

Note

If you are integrating your Cisco router into a European network, use the

dsl dsl-mode shdsl symmetric

annex

{

A

|

B

} command to choose annex B. The router uses annex A by default (United States).

Verify the Configuration

You can verify that the configuration is set the way you want by using the

show controllers dsl

command

from the privileged EXEC mode.

Router#

show controllers dsl 0

DSL 0 controller UP

SLOT 0: Globespan xDSL controller chipset

DSL mode: SHDSL Annex A

Frame mode: Utopia

Configured Line rate: Auto

Line Re-activated 6 times after system bootup

LOSW Defect alarm: ACTIVE

CRC per second alarm: ACTIVE

Line termination: CPE

Current 15 min CRC: 0

Current 15 min LOSW Defect: 0

Current 15 min ES Defect: 0

Current 15 min SES Defect: 0

Current 15 min UAS Defect: 33287

Previous 15 min CRC Defect: 0

Previous 15 min LOSW Defect: 0

Previous 15 min ES Defect: 0

Previous 15 min SES Defect: 0

Previous 15 min UAS Defect: 0

Line-0 status

Chipset Version: 0

Firmware Version: A388

Modem Status: Data, Status 1

Last Fail Mode: No Failure status:0x0

Line rate: 2312 Kbps

Framer Sync Status: In Sync

Rcv Clock Status: In the Range

Loop Attenuation: 341.1450 dB

Transmit Power: 7.5 dB

Step 6

ignore-error-duration

number

Example:

Router(config-controller)#

ignore-error-duration 15

Router(config-controller)#

Specifies how long, 15 to 30 seconds, to ignore

errors.

Step 7

exit

Example:

Router(config-controller)#

exit

Router(config)#

Exits controller configuration mode, returning to

global configuration mode.

Command

Purpose

Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide

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Chapter 4

Configuring PPP over ATM with NAT

Configure Network Address Translation

Receiver Gain: 22.5420 dB

SNR Sampling: 36.8590 dB

Dying Gasp: Present

Configure Network Address Translation

Network Address Translation (NAT) translates packets from addresses that match a standard access list,

using global addresses allocated by the dialer interface. Packets that enter the router through the inside

interface, packets sourced from the router, or both are checked against the access list for possible address

translation. You can configure NAT for either static or dynamic address translations.

Perform these steps to configure the outside ATM WAN interface with dynamic NAT, beginning in global

configuration mode:

Command

Purpose

Step 1

ip nat pool

name start-ip end-ip

{

netmask

netmask

|

prefix-length

prefix-length

}

Example:

Router(config)#

ip nat pool

pool1

192.168.1.0 192.168.2.0

netmask

255.255.255.0

Router(config)#

Creates pool of global IP addresses for NAT.

Step 2

ip nat inside source

{

list

access-list-number

}

{

interface

type number |

pool

name

} [

overload

]

Example 1:

Router(config)#

ip nat inside source list

1

interface dialer 0 overload

or

Example 2:

Router(config)#

ip nat inside source list

acl1 pool

pool1

Enables dynamic translation of addresses on the

inside interface.

The first example shows the addresses permitted

by the access list

1

to be translated to one of the

addresses specified in the dialer interface

0

.

The second example shows the addresses

permitted by access list

acl1

to be translated to one

of the addresses specified in the NAT pool

pool1

.

For details about this command and additional

parameters that can be set, as well as information

about enabling static translation, see the

Cisco IOS IP Command Reference, Volume 1 of 4:

Addressing and Services

.

Step 3

interface

type number

Example:

Router(config)#

interface

vlan 1

Router(config-if)#

Enters configuration mode for the VLAN (on

which the Fast Ethernet LAN interfaces

[FE0–FE3] reside) to be the inside interface for

NAT.