Dialer Profiles

A dialer profile separates configuration components from each other. Some items, such as physical interface characteristics, reside in one type of configuration, whereas others, such as a phone number, reside in another configuration. This setup lets you mix and match configuration components, depending on the need. Dialer interfaces are paired with physical interfaces as required.

Dialer profiles give fairly complex dial-up networks more flexibility in what they support. Gone are the days of mapping a single IP address or phone number to a serial port and using that interface to call only that one location. For this flexibility to take place, however, you need to define some new configurations.

When using a dialer profile to make calls, your options for encapsulation become more limited. You have the option of using Point-to-Point Protocol (PPP) or Cisco High-Level Data Link Control (HDLC). Dialer profiles do allow more flexibility when it comes to ISDN, though. You can set different call properties to different ISDN B channels, use different encapsulation types per B channel, put two B channels into separate dialer pools, and even configure B channels with separate network addresses.

Dialer Interface

A dialer interface is a logical interface that contains configuration information for a specific dial-up location. You can configure the dialer interface for most settings that normally go on a serial port. The dialer interface is where you configure an IP or other Layer 3 address, encapsulation type, compression, dialer maps, dialer string, remote device name, PPP authentication format, dialer-list number, dialer, group number, dialer-pool number, and dialer-idle timeout settings and, on asynchronous serial devices, a dialer inband.

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Understand that although a dialer interface is logically the same as a physical interface, it doesn't have many of the same physical characteristics configured on it. Watch out on the exam for answers that show physical characteristics being configured on the dialer interface.


You issue all the commands in Table 8.1 in interface dialer number configuration mode unless otherwise specified.

Table 8.1. Dialer Interface Commands

Command

Explanation

ip address address subnet-mask

Puts the specified IP address on the dialer interface.

dialer remote-name name

States the remote device name that the router is calling. This command is used to determine authentication.

dialer string string class map-class

Used to specify the phone number of the remote location. The class part of the command is optional and refers to a map class, which is covered later in this chapter.

dialer load-threshold load-value <inbound | outbound | either>

Specifies at what load level an additional line should be brought up in multilink (covered later in this book). The load-value is a range of 1 to 255 with 255 being 100% link utilization.

dialer hold-queue number

Sets up a set of buffers to hold packets. When dialing, there is a delay until the connection but no delay in arriving data. The number value is a range of 0 through 100 packets.

dialer pool number

Points the dialer interface to a dialer pool. The dialer pool is a group of physical interfaces that the dialer interface should use when making a call. Although a physical interface can be a member of multiple pools, you want a dialer interface pointing to one pool.

dialer-group number

Specifies which dialer-list command is used to determine interesting traffic.

dialer map protocol next-hop-address <name remote-device-name> <speed 56 | 64> <broadcast> <modem-script script-name> <system-script script-name> <phone-number-of-remote-device (ISDN-subaddress)>

The dialer map command is a fairly complex animal but allows for a lot of flexibility with dialer interfaces. The original dialer string command only lets you call one location, but the dialer map command lets you call multiple locations per interface. The protocol configuration wants a Layer 3 protocol followed by the address of the device you are connecting to. Every other command is optional. If you want to dial out, you also need to put in the remote device's phone number. The ISDN subaddress is also optional. This command must be last in the dialer-map statement.

PPP multilink

Establishes this interface as a member of a multilink relationship with other circuits.

PPP authentication <pap | chap | ms-chap>

States that when calling this location, the specified authentication type is used.

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Some components of the dialer map are required, depending on the circumstances. You use the name option with PPP authentication. Use speed when selecting between 56Kbps and 64Kbps ISDN channels. You need the broadcast option to send broadcast packets, such as RIP routing updates, across the wire. The modem-script and system-script commands let you use custom scripts per connection.


Remember that you can place multiple dialer maps on an interface, but they need to be pointing to different destinations. For example, you can use the same interface to make a connection to get information to the 20.0.0.0 network and call a number for the 30.0.0.0 network. These numbers can be the same; the router is only looking at the network in question. Once it figures out which network it needs to forward traffic to, it looks at the number linked to it and dials.

A sample dialer interface configuration follows:

 Dialer Interface 1        Ip address 192.168.4.9 255.255.255.252        Encapsulation ppp        Dialer remote-name corporate        PPP authentication chap        Dialer-group 5        Dialer pool 3        Dialer string 5551212        Dialer hold-queue 20 

Dialer Pools

A dialer pool is a group of physical interfaces. You need to configure each physical interface you want to be a member of the pool with a pool ID and priority information. Once an interface is a member of a pool, a dialer interface that uses the pool will use the physical interface that has the highest priority for an outgoing call. Use the dialer pool number priority priority command to configure it in interface configuration mode.

An interface may belong to multiple pools. If a pool contains multiple interfaces, you need to configure a priority level for the physical interface. When a router needs to make a call, it uses the highest priority available interface in the pool to make the next call.

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Just remember that physical interfaces are grouped into pools and may be part of more than one. A dialer interface uses a pool to decide which physical interface to use to make a call.


Listing 8.1 shows two Basic Rate Interfaces (BRIs) that are each configured to be members of two dialer pools.

Listing 8.1 Configuring pool membership
 Router(config)#interface BRI 0 Router(config-if)#dialer pool 1 priority 200 Router(config-if)#dialer pool 2 priority 150 Router(config)#interface BRI 1 Router(config-if)#dialer pool 1 priority 150 Router(config-if)#dialer pool 2 priority 200 

Map Classes

A map class is a useful part of a dialer profile. Although they are optional components, you can use them to specify different Layer 1 characteristics for a call. The commands in Table 8.2 tend to revolve around connection characteristics.

Table 8.2. Map Class Commands

Command

Explanation

map-class dialer class-name

This command creates a map class with the specified unique name and puts you in map class configuration mode.

dialer idle-timeout seconds

When a call is in progress but no interesting traffic is crossing the line, this command tells the router when to kill the link. By default, the router drops the line 120 seconds after the last piece of interesting traffic crosses.

dialer fast-idle seconds

If no interesting traffic is crossing a link and there are packets waiting to use the interface to call a different destination, the dialer fast idle timer kicks in. Rather than wait 2 minutes for the idle-timeout timer to expire, the fast idle timer only activates when there is contention for an interface and it expires much quicker. The default value of the timer is 20 seconds.

dialer wait-for-carrier-time seconds

This command is useful on analog lines because it tells the router how long to wait for a carrier signal. When used in conjunction with an asynchronous interface, the timer includes the time needed for the chat script to run. The default is 30 seconds, but Cisco recommends 60 seconds on asynchronous interfaces.

dialer isdn speed speed

This command gives you a choice between 56Kbps and 64Kbps when making a connection via ISDN. Check with your service provider to make sure it supports 64Kbps ISDN channels.



CCNP BCRAN Remote Access Exam Cram 2 (Exam Cram 640 - XXX)
CCNP BCRAN Remote Access Exam Cram 2 (Exam Cram 640 - XXX)
ISBN: N/A
EAN: N/A
Year: 2003
Pages: 183

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