Cisco Router 826 Routers Software Configuration Guide

							  
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Internet Access Scenarios
The Cisco 827 router is configured to act as a bridge on the WAN, so the data packets are bridged through 
the 6400 router onto the Internet. This network setup creates the simplicity of bridging data but also 
maintains router control. This network is very simple but limits more complex services such as stopping 
broadcast traffic. If you want more services available on your network, you may want to consider 
Scenario 2 or 3.
Configuring the Scenario
NoteIf you have only a single ATM PVC for your bridging network, you do not have to configure the protocol 
bridge broadcast.
This scenario includes configuration tasks and a configuration example. To add additional features to 
this network, see Chapter 3, “Basic Router Configuration,” and Chapter 4, “Advanced Router 
Configuration.”
After configuring your router, you need to configure the PVC endpoint. For a general configuration 
example, see “Cisco 3640 Gateway Configuration Example” at the end of this chapter.
Follow the steps below to replace a bridge or modem with the Cisco 827 router, beginning in global 
configuration mode. Each step includes the same values that are shown in the bridging configuration 
example at the end of this section.
Command Purpose
Step 1no ip routingDisables IP routing.
Step 2bridge 1 protocol ieeeSpecifies the bridge protocol to define the type of 
Spanning-Tree protocol.
Step 3interface ethernet 0Enters configuration mode for the Ethernet 
interface.
Step 4bridge-group 1Specifies the bridge-group number to which the 
Ethernet interface belongs. 
Step 5no shutdownEnables the Ethernet interface.
Step 6exitExits configuration mode for the Ethernet 
interface and the router.
Step 7interface ATM 0Enters configuration mode for the ATM interface.
Step 8pvc 8/35Creates an ATM permanent virtual circuit (PVC) 
for each end node with which the router 
communicates.
Step 9encapsulation aal5snapSpecifies the encapsulation type for the PVC. 
Step 10bridge-group 1Specifies the bridge-group number to which the 
ATM interface belongs. 
Step 11no shutdownEnables the ATM interface.
Step 12exit  Exits the configuration mode for the ATM 
interface. 
						

							  
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Configuration Example
The following is a configuration example for this network scenario. You do not have to enter the 
commands marked “default.” These commands appear automatically in the configuration file generated 
when you use the show running-config command.
no ip routing
!
interface Ethernet0
no ip address
no ip directed-broadcast (default)
bridge-group 1
!
interface ATM0
no ip address
no ip directed-broadcast (default)
pvc 8/35 
encapsulation aal5snap
!
bridge-group 1
!
ip classless (default)
!
bridge 1 protocol ieee
!
end
PPP over Ethernet with NAT
The Cisco 837 and SOHO 97 routers support a PPP-over-Ethernet (PPPoE) client, with Network 
Addressing Translation (NAT) and with multiple PCs on the LAN. Figure 2-6 shows a typical 
deployment scenario for PPPoE support. 
Figure 2-6 PPPoE Deployment Scenario
DSLAM Cisco 837/SOHO97
56956
3
2
1
4 
						

							  
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A PPPoE session is initiated on the client side by the Cisco 837 or SOHO 97 router. If the session has a 
timeout, or if the session is disconnected, the PPPoE client immediately attempts to reestablish the 
session. 
This section covers the following topics:
Configuring the Virtual Private Dial-Up Network Group Number
Configuring the ATM Interface
Configuring the Dialer Interface
Configuration Example
Configuring the Virtual Private Dial-Up Network Group Number
Follow the steps below to configure a virtual private dial-up network (VPDN), starting in global 
configuration mode. 1Multiple PCs in LAN3Access concentrator, concentrating data and 
LAN into ATM service over E1/T1 links
2Multiple PCs connected in a LAN4PPPoE session. A PPPoE session is initiated 
on the client side by the Cisco 837 and 
SOHO 97 routers
Command Purpose
Step 1vpdn enableEnables VPDN.
Step 2vpdn group tagSets the VPDN group.
Step 3request-dialinSpecifies the dialing direction.
Step 4protocol pppoeSpecifies the protocol type for the VPDN.
Step 5interface ATM0 
mtu 1492
pvc 8/35Enters configuration mode for the ATM interface. 
Sets the maximum transmission unit (MTU) size 
and PVC number.
Step 6pppoe-client dial-pool-number 1Defines the PPPoE client in dial pool number 1.
Step 7interface Dialer 1 ip address negotiated 
encapsulation ppp dialer-pool 1Enters configuration mode for the Dialer 1 
interface to obtain the IP address via IPCP. 
Specifies the encapsulation type for the PVC 
using dialer pool number 1. 
						

							  
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Configuring the ATM Interface
Follow the steps below to configure the ATM interface, beginning in global configuration mode. 
 
Configuring the Dialer Interface
Follow the steps below to configure the dialer interface, starting in global configuration mode. 
If you enter the clear vpdn tunnel pppoe command with a PPPoE client session already established, the 
PPPoE client session terminates, and the PPPoE client immediately tries to reestablish the session. Command Purpose
Step 1interface atm 0Enters configuration mode for the ATM interface. 
Step 2dsl linerate {number | auto} Specifies the DSL line rate. The range of valid 
numbers is from 72 to 2312. Note that this 
command is applicable only to Cisco 828 and 
SOHO 78 routers.
Step 3ip address 200.200.100.1 255.255.255.0Sets the IP address and subnet mask for the ATM 
interface.
Step 4pvc vpi/vciCreates an ATM PVC for each end node with 
which the router communicates.
Step 5ppoe-client dial-pool-number 1Binds the dialer to the interface.
Step 6no shutdownEnables the ATM 0 interface.
Command Purpose
Step 1ip route default-gateway-ip-address mask dialer 
0Sets the IP route for the default gateway for the 
Dialer 0 interface.
Step 2interface dialer 0Enters the Dialer 0 interface configuration.
Step 3ip address negotiatedSpecifies that the IP address is to be negotiated 
over PPP.
Step 4ip mtu 1492Sets the size of the IP maximum transmission unit 
(MTU).
Step 5encapsulation pppSets the encapsulation type to PPP.
Step 6dialer pool 1Specifies the dialer pool to be used.
Step 7dialer-group 1Assigns this interface to a dialer list.
Step 8ppp authentication chapSets the PPP authentication method to Challenge 
Handshake Authentication Protocol (CHAP).
Step 9exitExits the Dialer 0 interface configuration.
Step 10dialer-list 1 protocol ip permitCreates a dialer list for interested packets to be 
forwarded through the specified interface dialer 
group.  
						

							  
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Configuration Example
The following example shows a configuration of a PPPoE client.
vpdn enable
vpdn-group 1
request-dialin
protocol pppoe
!
interface atm0
no ip address
no atm ilmi-keepalive
pvc 1/100
pppoe-client dial-pool-number 1
!
interface dialer 1
ip address negotiated
ppp authentication chap
dialer pool 1
dialer-group 1
!
dialer-list 1 protocol ip permit
PPP over Ethernet with NAT Using a Dial-on-Demand PPP-over- Ethernet 
Connection
The Cisco 831, Cisco 836, Cisco 837, Cisco SOHO 91, Cisco SOHO 96, and Cisco SOHO 97 routers 
support a PPP-over-Ethernet (PPPoE) client, using a dial-on-demand PPP-over-Ethernet connection. For 
deployment scenario, see Figure 2-6 on page 2-8.
Configuring the Virtual Private Dial-Up Network Group Number
Complete the following tasks to configure a VPDN, starting in global configuration mode. 
Configuring the ATM Interface
Follow the steps below to configure the ATM interface, beginning in global configuration mode. Command Purpose
Step 1vpdn enableEnables VPDN.
Step 2vpdn group tagSets the VPDN group.
Step 3request-dialinSpecifies the dialing direction.
Step 4protocol pppoeSpecifies the protocol type for the VPDN.
Command Purpose
Step 1interface atm 0Enters configuration mode for the ATM interface. 
Step 2ip address 200.200.100.1 255.255.255.0Sets the IP address and subnet mask for the ATM 
interface. 
						

							  
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Configuring the Dialer Interface
Follow the steps below to configure the dialer interface, starting in global configuration mode. 
If you enter the clear vpdn tunnel pppoe command with a PPPoE client session already established, the 
PPPoE client session terminates, and the PPPoE client immediately tries to reestablish the session. 
Configuration Example
The following example shows a configuration of a PPPoE client.
interface Ethernet0
no ip address
ip tcp adjust-mss 1400
no keepalive
hold-queue 100 out
!
vpdn enable
vpdn-group 1
request-dialin
protocol pppoe
!
Step 3pvc vpi/vciCreates an ATM PVC for each end node with 
which the router communicates.
Step 4ppoe-client dial-pool-number 1 
dial-on-demandBinds the dialer to the interface.
Step 5no shutdownEnables the ATM 0 interface. Command Purpose
Command Purpose
Step 1ip route default-gateway-ip-address mask dialer 
0Sets the IP route for the default gateway for the 
Dialer 0 interface.
Step 2interface dialer 0Enters Dialer 0 interface configuration.
Step 3ip address negotiatedSpecifies that the IP address is to be negotiated 
over PPP.
Step 4ip mtu 1492Sets the size of the IP maximum transmission unit 
(MTU).
Step 5ip nat outsideEstablishes the Dialer 0 interface as the outside 
interface.
Step 6encapsulation pppSets the encapsulation type to PPP.
Step 7dialer pool 1Specifies the dialer pool to be used.
Step 8dialer-group 1Assigns this interface to a dialer list.
Step 9ppp authentication chapSets the PPP authentication method to Challenge 
Handshake Authentication Protocol (CHAP).
Step 10exitExits the Dialer 0 interface configuration.
Step 11dialer-list 1 protocol ip permitCreates a dialer list for packets of interest to be 
forwarded through the interface dialer group.  
						

							  
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interface atm0
no ip address
no atm ilmi-keepalive
pvc 1/100
pppoe-client dial-pool-number 1 dial-on-demand
!
interface dialer 1
ip address negotiated
ppp authentication chap
dialer pool 1
dialer-group 1
!
dialer-list 1 protocol ip permit
PPP over ATM with NAT
This network shows a user connected to the Internet through PPP over ATM and one static IP address. 
You may want to use this scenario in your network if you want to access the network with ATM support 
at the endpoints. PPP over ATM provides a network solution with simplified address handling and gives 
straight user verification as you would get in a dial network. 
Figure 2-7 shows the network topology for this scenario.
Figure 2-7 PPP over ATM with NAT
In this scenario, the small business or remote user on the Ethernet LAN can connect to the Internet 
through ADSL. The Ethernet interface carries the data packet through the LAN and offloads it to the PPP 
connection on the ATM interface. The dialer interface is used to connect to the Internet or the corporate 
office. The number of ATM PVCs is set by default.
NAT (represented as the dashed line at the edge of the 827 routers) signifies two addressing domains and 
the inside source address. The source list defines how the packet travels through the network.
The following configuration topics are covered in this section:
Configuring the Ethernet Interface
Configuring the Dialer Interface
Configuring the ATM Interface 1Small business or remote user3PPP over ATM PVC 8/35
2Connection to Ethernet 0 address 
192.168.1.1/24 through a dialer interface4The Internet
Cisco 827/827-4V
192.168.1.1/24DSLAMCisco
6400 Cisco 6400
74578
14
3
2 
						

							  
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Configuring NAT
Configuration Example
To add additional features to this network, seeChapter 3, “Basic Router Configuration” and Chapter 4, 
“Advanced Router Configuration.”
After configuring your router, you need to configure the PVC endpoint. For a general configuration 
example, see“Cisco 3640 Gateway Configuration Example” at the end of this chapter.
Configuring the Ethernet interface
Follow the steps below to configure the Ethernet interface, beginning in global configuration mode.
Configuring the Dialer Interface
Follow the steps below to configure the dialer interface, beginning in global configuration mode.
Configuring the ATM Interface
Follow the steps below to configure the ATM interface, beginning in global configuration mode.Command Purpose
Step 1interface ethernet 0Enters configuration mode for the Ethernet 
interface.
Step 2ip address 192.168.1.1 255.255.255.0Sets the IP address and subnet mask for the 
Ethernet interface.
Step 3no shutdownEnables the interface and configuration changes 
just made to the Ethernet interface.
Step 4exitExits configuration mode for the Ethernet 
interface.
Command Purpose
Step 1interface dialer 0Enters configuration mode for the dialer interface.
Step 2ip address negotiatedConfigures a negotiated IP address.
Step 3ip nat outsideSets the interface to be connected to the outside 
network.
Step 4encapsulation pppSpecifies the encapsulation type for the PVC to be 
PPP. 
Step 5dialer pool 1Specifies which dialer pool number you are using.
Step 6exitExits configuration mode for the dialer interface.
Command Purpose
Step 1interface ATM 0Enters configuration mode for the ATM interface.
Step 2pvc 8/35Creates an ATM PVC for each end node with 
which the router communicates. 
						

							  
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Configuring NAT
Follow the steps below to configure NAT, beginning in global configuration mode.
Configuration Example
In the following configuration example, you do not have to enter the commands marked “default.” These 
commands appear automatically in the configuration file generated when you use the show 
running-config command.
interface Ethernet0
ip address 192.168.1.1 255.255.255.0
no ip directed-broadcast (default)
ip nat inside
!
interface ATM0
no ip address
no ip directed-broadcast (default)
ip nat outside
no atm ilmi-keepalive (default)
pvc 8/35 
encapsulation aal5mux ppp dialer
dialer pool-member 1
Step 3encapsulation aal5mux ppp dialerSpecifies the encapsulation type for the PVC to be 
aal5mux (PPP) and point back to the dialer 
interface. 
Step 4dialer pool-member 1Specifies a dialer pool-member.
Step 5no shutdownEnables interface and configuration changes just 
made to the ATM interface.
Step 6exitExits configuration mode for the ATM interface. Command Purpose
Command Purpose
Step 1ip nat inside source list 1 interface dialer 0 
overloadEnables dynamic translation of addresses 
permitted by the access list to one of addresses 
specified in the dialer interface.
Step 2ip route 0.0.0.0.0.0.0.0 dialerSets the ip route to point to the dialer interface as 
a default gateway.
Step 3access-list 1 permit 192.168.1 0 0.0.0.255Defines a standard access list permitting 
addresses that need translation.
Step 4interface ethernet 0Enters configuration mode for the Ethernet 
interface.
Step 5ip nat insideEstablishes the Ethernet interface as the inside 
interface.
Step 6no shutdownEnables interface and configuration changes just 
made to the Ethernet interface.
Step 7exitExits configuration mode for the Ethernet 
interface. 
						

							  
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Configuring Dial Backup
!
bundle-enable
!
interface Dialer0
ip address negotiated
no ip directed-broadcast (default)
ip nat outside
encapsulation ppp 
dialer pool 1
!         
ip nat inside source list 1 interface Dialer0 overload
ip classless (default)
ip route 0.0.0.0 0.0.0.0 Dialer 0 (default gateway)
!
access-list 1 permit 192.168.1.0 0.0.0.255
!
end
Configuring Dial Backup
By allowing you to configure a backup modem line connection, dial backup provides protection against 
WAN downtime. Dial backup is inactive until it is configured. On Cisco 831, Cisco 837, 
Cisco SOHO 91, and Cisco SOHO 97 routers, both the console port and the auxiliary port in the 
Cisco IOS software configuration are on the same physical RJ-45 port. Therefore, both ports cannot be 
activated simultaneously, and the command-line interface (CLI) must be used to enable or disable either 
one.
Like the Cisco 831 and Cisco 837 routers and the Cisco SOHO 91 and Cisco SOHO 97 routers, the 
Cisco 836 router supports dial-in (for remote management) and dial-out (for dial backup) capabilities 
across the ISDN interface. The Cisco SOHO 96 router supports only the dial-in feature. Unlike the 
Cisco 831 and Cisco 837 routers and the Cisco SOHO 91 and Cisco SOHO 97 routers, the dial backup 
and remote management functions are configured on the Cisco 836 and Cisco SOHO 96 routers through 
the router’s ISDN S/T port. 
NoteThe remote management described in the “Configuring Dial Backup and Remote Management for the 
Cisco 837 and Cisco SOHO 97 Routers” section on page 2-19 refers to backup remote management, the 
function that allows external control of the router via the ISDN when the ATM link goes down.
Dial Backup Feature Limitations and Configuration
This section discusses the limitations and configuration of the dial backup feature on the Cisco 831, 
Cisco 836, and Cisco 837 routers and the Cisco SOHO 91, Cisco SOHO 96, and Cisco SOHO 97 routers. 
Cisco 836 and Cisco 837 Routers and Cisco SOHO 96 and Cisco SOHO 97 Routers
The following can be used to bring up the dial backup feature in the Cisco IOS software for the Cisco 836 
and Cisco 837 routers and the Cisco SOHO 96 and Cisco SOHO 97 routers:
Backup Interfaces
Floating Static Routes
Dialer Watch