This document provides a sample configuration that illustrates an asymmetric digital subscriber line (ADSL)-bridge configuration with Network Address Translation (NAT). This configuration has been tested to work with the residential ADSL service of the Pacific Bell and can be used to replace the Alcatel ADSL modem provided by Pacific Bell.
In order to "route" the Ethernet segment to the Internet, as well as "bridge" between your site and Pacific Bell, use the bridge irb command.
The internal network appears to the Internet (and Pacific Bell) as a single host because NAT is used, and the single host visible to the outside world is the Bridge Virtual Interface (BVI).
Do not include the Ethernet in your bridge group since you probably do not want your internal traffic bridged to the public network.
This configuration also makes the router a Dynamic Host Configuration Protocol (DHCP) server for the internal network. This offers private addresses from 192.168.1.1 to 192.168.1.253, offers Domain Naming System (DNS) servers to Pacific Bell, and gives the Pacific Bell its own address at the default gateway.
Ensure that you meet these requirements before you attempt this configuration:
Cisco IOS® Software Release 12.0(3)T
Residential ADSL service of Pacific Bell
This configuration is known to work with this:
------------------ show version ------------------ Cisco Internetwork Operating System Software IOS (tm) 1400 Software (C1400-NOSY-M), Version 12.0(5)T1, RELEASE = SOFTWARE (fc1) Copyright (c) 1986-1999 by cisco Systems, Inc. Compiled Tue 17-Aug-99 10:29 by cmong Image text-base: 0x02005000, data-base: 0x0277197C ROM: System Bootstrap, Version 12.0(3)T, RELEASE SOFTWARE (fc1) ROM: 1400 Software (C1400-RBOOT-R), Version 12.0(3)T, RELEASE SOFTWARE = (fc1) Router1417 uptime is 5 days, 11 hours, 15 minutes System returned to ROM by power-on System restarted at 11:05:59 UTC Thu Nov 25 1999 System image file is "flash:c1400-nosy-mz.120-5.T1" cisco 1417 (68360) processor (revision D) with 13312K/3072K bytes of = memory. Processor board ID 14520795, with hardware revision 00000000 Bridging software. X.25 software, Version 3.0.0. 1 Ethernet/IEEE 802.3 interface(s) 1 ATM network interface(s) System/IO memory with parity disabled 8192K bytes of DRAM onboard 8192K bytes of DRAM on SIMM System running from RAM 7K bytes of non-volatile configuration memory. 4096K bytes of processor board PCMCIA flash (Read/Write) Configuration register is 0x2102
This document is not restricted to specific software and hardware versions.
The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.
Refer to the Cisco Technical Tips Conventions for more information on document conventions.
In this section, you are presented with the information to configure the features described in this document.
This document uses this network setup:
This document uses these configurations:
------------------ show running-config ------------------ Building configuration... Current configuration: ! ! Last configuration change at 21:13:19 UTC Tue Nov 30 1999 ! NVRAM config last updated at 21:14:45 UTC Tue Nov 30 1999 ! version 12.0 service timestamps debug datetime msec service timestamps log datetime msec service password-encryption service udp-small-servers service tcp-small-servers ! hostname Router1417 ! enable password 0 letmein ! ! ! ! ! ip subnet-zero no ip domain-lookup ip dhcp excluded-address 192.168.1.254 ! ip dhcp pool ippool1417 network 192.168.1.0 255.255.255.0 dns-server 126.96.36.199 188.8.131.52 default-router 192.168.1.254 ! bridge irb ! ! process-max-time 200 ! interface Loopback1 no ip address no ip directed-broadcast ! interface Ethernet0 ip address 192.168.1.254 255.255.255.0 no ip directed-broadcast ip nat inside ! interface ATM0 no ip address no ip directed-broadcast atm vc-per-vp 64 no ATM ilmi-keepalive pvc 8/35 encapsulation aal5snap ! bridge-group 1 ! interface BVI1 ip address <cust-router-ip> 255.255.255.0 no ip directed-broadcast ip Nat outside ! ip default-gateway <pbi-router-ip> ip Nat pool pbi <cust-router-ip> <cust-router-ip> prefix-length 24 ip Nat inside source list 10 pool pbi overload ip classless ip route 0.0.0.0 0.0.0.0 <pbi-router-ip> permanent ip http server ! access-list 10 permit 192.168.1.0 0.0.0.255 bridge 1 protocol ieee bridge 1 route ip ! line con 0 transport input none line vty 0 4 password 0 letmein login ! end
Use this section to confirm that your configuration works properly.
show interface ATM 0—If the line is down, check the cabling.
show ip nat translations—In order to see if it is necessary to translate addresses for each internal client.
debug atm events—In order to look for the modem state:
0x8 means that the modem waits to hear from central office (CO). This probably means that you do not have a good connection to the CO. Check the connection and make sure that the correct cable is used.
0x10 means that the modem heads from the CO and now trains. The CO is connected, and the modems attempt to negotiate a connection. If it fails in this state, there is probably an incompatibility between the ADSL interface of the Cisco 1417 and the CO. Make sure that the correct virtual path identifier/virtual channel identifier (VPI/VCI) is used.
0x20 means that activation is completed, and the link is up.
This section provides information you can use to troubleshoot your configuration.
Note: Refer to Important Information on Debug Commands before you use debug commands.
The Cisco Support Community is a forum for you to ask and answer questions, share suggestions, and collaborate with your peers.
Refer to Cisco Technical Tips Conventions for information on conventions used in this document.