- Cisco 860, Cisco 880, and Cisco 890 Series Integrated Services Routers Software Configuration Guide
Table Of Contents
Configuring PPP over ATM with NAT
Configure the Dialer Interface
Configure the ATM WAN Interface
Configure DSL Signaling Protocol
Configure Network Address Translation
Configuring PPP over ATM with NAT
This chapter provides an overview of Point-to-Point Protocol over Asynchronous Transfer Mode (PPPoA) clients and network address translation (NAT) that can be configured on the Cisco 860 and Cisco 880 series Integrated Services Routers (ISRs).
Multiple PCs can be connected to the LAN behind the router. Before traffic from the PCs is sent to the PPPoA session, it can be encrypted, filtered, and so forth. PPP over ATM provides a network solution with simplified address handling and straight user verification like a dial network. Figure 12-1 shows a typical deployment scenario with a PPPoA client and NAT configured on the Cisco router. This scenario uses a single static IP address for the ATM connection.
Figure 12-1 PPP over ATM with NAT
In this scenario, the small business or remote user on the Fast Ethernet LAN can connect to an Internet service provider (ISP) using the integrated xDSL WAN interface on the Cisco 860 and Cisco 880 series ISRs.
The Fast Ethernet interface carries the data packet through the LAN and off-loads it to the PPP connection on the ATM interface. The ATM traffic is encapsulated and sent over the xDSL interface. The dialer interface is used to connect to the ISP.
PPPoA
The PPPoA Client feature on the router provides PPPoA client support on ATM interfaces. A dialer interface must be used for cloning virtual access. Multiple PPPoA client sessions can be configured on an ATM interface, but each session must use a separate dialer interface and a separate dialer pool.
A PPPoA session is initiated on the client side by the Cisco 860 or Cisco 880 series router.
NAT
NAT (represented as the dashed line at the edge of the Cisco router) signifies two addressing domains and the inside source address. The source list defines how the packet travels through the network.
Configuration Tasks
Perform the following tasks to configure this network scenario:
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Configure the Dialer Interface
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An example showing the results of these configuration tasks is shown in the "Configuration Example" section.
Configure the Dialer Interface
The dialer interface indicates how to handle traffic from the clients, including, for example, default routing information, the encapsulation protocol, and the dialer pool to use. It is also used for cloning virtual access. Multiple PPPoA client sessions can be configured on an ATM interface, but each session must use a separate dialer interface and a separate dialer pool.
Perform these steps to configure a dialer interface for the ATM interface on the router, starting in global configuration mode.
Repeat these steps for any additional dialer interfaces or dialer pools needed.
Configure the ATM WAN Interface
Perform these steps to configure the ATM interface, beginning in global configuration mode.
Step 1
interface type number
Example:
Router(config)# interface atm 0Router(config-if)#Enters interface configuration mode for the ATM interface (labeled ADSLoPOTS or G.SHDSL on the back of your router).
Note
Step 2
pvc vpi/vci
Example:
Router(config-if)# pvc 8/35Router(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 dialerRouter(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 1Router(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.
Step 5
no shutdown
Example:
Router(config-if-atm-vc)# no shutdownRouter(config-if)#Enables interface and configuration changes just made to the ATM interface.
Step 6
exit
Example:
Router(config-if)# exitRouter(config)#Exits configuration mode for the ATM interface.
Configure DSL Signaling Protocol
DSL signaling must be configured on the ATM interface for connection to your ISP. The Cisco 887 and Cisco 867 ISRs support ADSL signaling over POTS and the Cisco 886 ISR supports ADSL signaling over ISDN. The Cisco 888 ISR supports G.SHDSL.
Configuring ADSL
The default configuration for ADSL signaling is shown in Table 12-1.
If you wish to change any of these settings, use one of the following commands in global configuration mode.
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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.
Router# show dsl interface atm 0ATM0Alcatel 20190 chipset informationATU-R (DS) ATU-C (US)Modem Status: Showtime (DMTDSL_SHOWTIME)DSL Mode: ITU G.992.5 (ADSL2+) Annex AITU STD NUM: 0x03 0x2Chip Vendor ID: 'STMI' 'BDCM'Chip Vendor Specific: 0x0000 0x6193Chip Vendor Country: 0x0F 0xB5Modem Vendor ID: 'CSCO' ' 'Modem Vendor Specific: 0x0000 0x0000Modem Vendor Country: 0xB5 0x00Serial Number Near:Serial Number Far:Modem VerChip ID: C196 (3)DFE BOM: DFE3.0 Annex A (1)Capacity Used: 82% 99%Noise Margin: 12.5 dB 5.5 dBOutput Power: 11.5 dBm 12.0 dBmAttenuation: 5.5 dB 0.0 dBFEC ES Errors: 0 0ES Errors: 1 287SES Errors: 1 0LOSES Errors: 1 0UES Errors: 0 276233Defect Status: None NoneLast Fail Code: NoneWatchdog Counter: 0x56Watchdog Resets: 0Selftest Result: 0x00Subfunction: 0x00Interrupts: 4147 (0 spurious)PHY Access Err: 0Activations: 3LED Status: ONLED On Time: 100LED Off Time: 100Init FW: init_AMR-4.0.015_no_bist.binOperation FW: AMR-4.0.015.binFW Source: embeddedFW Version: 4.0.15DS Channel1 DS Channel0 US Channel1 US Channel0Speed (kbps): 0 19999 0 1192Cells: 0 0 0 1680867Reed-Solomon EC: 0 0 0 0CRC Errors: 0 0 0 326Header Errors: 0 0 0 131Total BER: 0E-0 65535E-0Leakage Average BER: 0E-0 65535E-255Interleave Delay: 0 36 0 11ATU-R (DS) ATU-C (US)Bitswap: enabled enabledBitswap success: 0 0Bitswap failure: 0 0LOM Monitoring : DisabledDMT Bits Per Bin000: 0 0 0 0 F F F F F F F F F F F F010: 0 0 3 0 F F F F F F F F F F F F020: F F F F F F F F F F F F F F F F....DSL: Training log buffer capability is not enabledRouter#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:
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 255.255.255.0Router(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 overloador
Example 2:
Router(config)# ip nat inside source list acl1 pool pool1Enables 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 1Router(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.
Step 4
ip nat {inside | outside}
Example:
Router(config-if)# ip nat insideRouter(config-if)#Applies NAT to the Fast Ethernet LAN interface as the inside interface.
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 5
no shutdown
Example:
Router(config-if)# no shutdownRouter(config-if)#Enables the configuration changes just made to the Ethernet interface.
Step 6
exit
Example:
Router(config-if)# exitRouter(config)#Exits configuration mode for the Fast Ethernet interface.
Step 7
interface type number
Example:
Router(config)# interface atm 0Router(config-if)#Enters configuration mode for the ATM WAN interface (ATM0) to be the outside interface for NAT.
Step 8
ip nat {inside | outside}
Example:
Router(config-if)# ip nat outsideRouter(config-if)#Identifies the specified WAN interface as the NAT outside interface.
For details about this command and additional parameters that can be set, as well as enabling static translation, see the Cisco IOS IP Command Reference, Volume 1 of 4: Addressing and Services.
Step 9
no shutdown
Example:
Router(config-if)# no shutdownRouter(config-if)#Enables the configuration changes just made to the Ethernet interface.
Step 10
exit
Example:
Router(config-if)# exitRouter(config)#Exits configuration mode for the ATM interface.
Step 11
access-list access-list-number {deny | permit} source [source-wildcard]
Example:
Router(config)# access-list 1 permit 192.168.1.0 255.255.255.0Defines a standard access list permitting addresses that need translation.
Note
Note
For complete information on NAT commands, see the Cisco IOS Release 12.3 documentation set.
Configuration Example
The following configuration example shows a portion of the configuration file for a client in the PPPoA scenario described in this chapter.
The VLAN interface has an IP address of 192.168.1.1 with a subnet mask of 255.255.255.0. NAT is configured for inside and outside.
Note
!interface Vlan1ip address 192.168.1.1 255.255.255.0ip nat insideip virtual-reassembly (default)!interface ATM0no ip addressip nat outsideip virtual-reassemblyno atm ilmi-keepalivepvc 8/35encapsulation aal5mux ppp dialerdialer pool-member 1!dsl operating-mode auto!interface Dialer0ip address negotiatedip mtu 1492encapsulation pppdialer pool 1dialer-group 1ppp authentication chap!ip classless (default)!ip nat pool pool1 192.168.1.0 192.168.2.0 netmask 0.0.0.255ip nat inside source list 1 interface Dialer0 overload!access-list 1 permit 192.168.1.0 0.0.0.255dialer-list 1 protocol ip permitip route 10.10.25.2 0.255.255.255 dialer 0!Verifying Your Configuration
Use the show ip nat statistics command in privileged EXEC mode to verify the PPPoA client with NAT configuration. You should see verification output similar to the following example:
Router# show ip nat statisticsTotal active translations: 0 (0 static, 0 dynamic; 0 extended)Outside interfaces:ATM0Inside interfaces:Vlan1Hits: 0 Misses: 0CEF Translated packets: 0, CEF Punted packets: 0Expired translations: 0Dynamic mappings:-- Inside Source[Id: 1] access-list 1 interface Dialer0 refcount 0Queued Packets: 0
