| Use the set
encapsulation ppp command if
you want PPP encapsulation for your ISDN interface and if you want
any of the Link Control Protocol (LCP) options that PPP offers (for
example, CHAP authentication). You must use PPP, PAP, or CHAP if you
will receive calls from more than one dialup source. This command
must be entered if you are connecting to a Cisco IOS software-based
router.
In addition to these commands, each
user profile must include the user's username (set
user username), IP
address (set ip address ip
address),
and subnet mask (set ip
netmask netmask). You
must also turn on IP routing using the set ip routing on command. If
you do not include the subnet mask, the default mask for that class
of address is assumed. As an example, if you are using the address
172.16.2.53 without configuring a network mask, the Cisco 700
assumes the mask to be 255.255.0.0, which is the default mask for a
Class B address.
If you want to route IP with PPP, you
must turn off Combinet Proprietary Protocol (CPP) by using the set
encapsulation ppp command.
Routing IP using CPP is recommended
only for connections between Cisco 700 products, not between a Cisco
700 series router and a Cisco IOS software-based router. To route
between non-CPP products, you should configure IP routing with PPP.
With Version 4.1 of the Cisco IOS 700, encapsulation with PPP is the
default.
The set number
number
command configures the phone number that is used to dial the ISP or
remote router. This command is used in a user profile. The following
is an example of this command:
IOS-700:User3>set
number 14085551234
Enabling Profiles
A connection is a dynamically
created link to a remote site. Connections are closely related to
profiles because all connections are associated with a profile that
defines the configuration of the connection.
A virtual connection is a
connection without any existing physical channels. An active
connection is a connection with one or more existing
physical channels. Profiles can be set to be either active or
inactive. When a profile has been created, setting it to active
creates a virtual connection to the associated remote device. After
a call is made to the associated remote device, the connection
becomes an active connection.
Virtual and active connections behave
similarly. The only difference is that active connections are
forwarding packets. Virtual connections exist in order to monitor
packet traffic until a demand filter causes a call to be initiated.
When this happens, the virtual connection becomes an active
connection.
When the call is finished, the
physical link between the two devices is disconnected. However, the
virtual connection to the remote router might be configured to
remain active.
If the profile is configured to
remain active after a link disconnects, a virtual connection
remains. The virtual connection monitors the LAN traffic. If packets
destined for the WAN are detected, the router opens up the physical
connection and forwards the packets.
If the remote user makes a call to
you, the remote device is identified and associated with the virtual
connection created by the user’s profile. This causes the
connection to become active.
When creating a profile, it can be
set active or inactive by using the set active profile-name or
the set inactive profile-name commands.
Setting IP Default Routes
For the user profile specified,
usually the central-site router ,
you can enter the default route and point it at a specific address,
as follows:
700:user>set ip route destination
0.0.0.0/0 gateway 0.0.0.0 propagate on cost 1
The address used is the IP address of
the BRI interface central site router. All traffic for this user
goes to the same IP address. To enable static routes, you must also
set bridging off and make the central site user profile active by
using the commands in Figure .
Normally the propagate on
command is not used because it will cause the BRI link to come up
whenever there is a routing update.
Configuring IP Routing
In Example ,
the Cisco 700 router (R700) has a static route to the (Cisco IOS) router
Central, as shown in Figure .
Only the LAN and USER
profiles are shown. You must also configure the system profile for
the Cisco 700 router. The router-configuration information must be
supplied by the ISP, and it depends on the configuration of the ISP
and the switch type.
The PPP IP Control Protocol (IPCP)
allows for the negotiation of certain parameters, such as an IP
address and a specific compression protocol. Some points to remember
when using IPCP negotiation on a Cisco 700 series router follow:
- A user profile is
required to run PPP. IP routing must be turned on in order to
receive an IPCP negotiated address.
- If a manually
configured IP address exists on the Internal profile, the IPCP
address will be assigned to the WAN (user) profile.
- If a manually
configured IP address exists on the LAN profile, the IPCP
address will be assigned to the internal profile.
- If the LAN IP
address is manually configured, the WAN interface must be
unnumbered because the IPCP address will be assigned to the
internal profile.
- The remote site
router needs to be configured to hand off IPCP addresses. A
sample configuration for the remote router (central) to hand off
an IPCP address follows:
Central(config)#ip local pool
test 700 192.150.3.10 192.150.3.19
Central(config)#interface bri0
Central(config-if)#peer default
ip address pool test
This configuration specifies the IP
address to be used when the Cisco 700 dials into the central site.
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