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Chapter 7      Router Feature Configuration
Configuring Multilink PPP Fragmentation and Interleaving
For complete information on the PPP fragmentation and interleaving commands, 
refer to the Dial Solutions Configuration Guide for Cisco IOS Release 12.0T. For 
general information on PPP fragmentation and interleaving concepts, see 
Chapter 1, “Concepts.” 
Configuration Example
The following configuration defines a dialer interface that enables multilink PPP 
with interleaving and a maximum real-time traffic delay of 20 ms. The 
encapsulation type is defined as aal5mux.
You do not need to enter the commands marked “default.” These commands 
appear automatically in the configuration file generated when you use the 
show running-config command.
Step 3bandwidth nSpecify the bandwidth number associated 
with the PVC that is using the dialer interface, 
where n is the value of the sustained cell rate 
(SCR) parameter of the PVC using that dialer 
interface.This is important because otherwise 
the dialer interface will assume a value of 
100 kbps if a specific class of service is 
configured.
Step 4ppp multilink interleaveEnable interleaving for RTP packets among 
the fragments of larger packets on a multilink 
PPP bundle.
Step 5ppp multilink fragment-delay millisecondsConfigure a maximum fragment delay of 
20 ms. This command is optional.
Step 6ip rtp reserve lowest-UDP-port 
range-of-ports [maximum-bandwidth]Reserve a special queue for real-time packet 
flows to specified destination UDP ports, 
allowing real-time traffic to have higher 
priority than other flows. 
Step 7exitExit configuration mode for the dialer 
interface. Command Task 
						

							 
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interface dialer 1
ppp multilink
encapsulated ppp
ppp multilink interleave
bandwidth 640
ppp multilink fragment-delay 20
ip rtp reserve 16384 100 64
!
interface ATM0
pvc 8/35
encapsulation aal5mux ppp dialer
dialer pool-member 1
Verifying Your Configuration
To verify that you have properly configured PPP fragmentation and interleaving, 
enter the debug ppp multilink fragment command, and then send out one 
1500-byte ping packet. The debug message will display information about the 
fragments being transmitted.
Configuring IP Precedence
IP Precedence gives voice packets higher priority than other IP data traffic. 
Complete the following steps to configure real-time voice traffic precedence over 
other IP network traffic, beginning in global configuration mode.
Command Task
Step 1configure terminalEnter configuration mode.
Step 2dial-peer voice number voipEnter the dial peer configuration mode to 
configure a VoIP dial peer.
Step 3destination-pattern numberSet a destination pattern.
Step 4ip precedence numberSelect a precedence level for the voice traffic 
associated with that dial peer. 
						

							 
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NoteIn IP Precedence, the numbers 1 through 5 identify classes for IP flows; the 
numbers 6 through 7 are used for network and backbone routing and updates.
For complete information on the IP Precedence commands, refer to the Cisco IOS 
Release 12.0 documentation set. For general information on IP precedence, see 
Chapter 1, “Concepts.” 
Configuration Example
This configuration example shows a voice configuration with IP Precedence set. 
The IP destination target is set to 8 dialing digits, which automatically sets the IP 
precedence to 5 on the Cisco routers. The dial peer session target is RAS, which 
is a protocol that runs between the H.323 voice protocol gateway and gatekeeper.
You do not need to enter the commands marked “default.” These commands 
appear automatically in the configuration file that is generated when you use the 
show running-config command.
!
access-list 101 permit
route-map data permit 10
set ip precedence routing
!
Configuring Voice
The Cisco 827 voice-enabled routers support voice using the H.323 signaling 
protocol as the default signaling protocol. Command Task
Step 1configure dial-peerEnter configuration mode for the dial peer. 
Step 2dial-peer voice number voipAssign the dial peer voice number to 
configure a VoIP dial peer.  
						

							 
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Prerequisite Tasks
Before you can configure your router to use voice, you need to perform the 
following tasks:
Establish a working IP network. 
Complete your company dial plan.
Establish a working telephony network based on your company dial plan.
Integrate your dial plan and telephony network into your existing IP network 
topology. 
Configuring Voice for H.323 Signaling
This section describes the tasks you need to perform to configure the router for 
H.323 signaling on the voice ports.
Configuring the POTS Dial Peers
Use the following steps to configure the POTS dial peers, beginning in global 
configuration mode.
Configuring Voice Dial Peers for H.323 Signaling
Complete the following steps to configure voice dial peers for H.323 signaling, 
beginning in global configuration mode. Command Task
Step 1dial-peer voice number POTSEnter configuration mode for the dial peer.
Step 2destination-pattern stringDefine the destination telephone number 
associated with the VoIP dial peer.
Step 3port numberSpecify the port number. 
						

							 
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Configuring Voice Ports for H.323 Signaling
Voice port configuration should be automatic in the United States; however, for 
configuration outside the United States, you may follow the steps below to 
configure the voice port, beginning in global configuration mode. Command Task
Step 1dial-peer voice number Vo I PEnter configuration mode for the dial peer.
Step 2destination-pattern stringDefine the destination telephone number 
associated with each VoIP dial peer. 
Step 3codec string  Specify a codec if you are not using the 
default codec of g.729. 
Step 4session target {ipv4:destination-address} Specify a destination IP address for each dial 
peer.
Command Task
Step 1configure dial-peerEnter configuration mode for the dial peer. 
Step 2voice-port portIdentify the voice port you want to configure 
and enter the voice port configuration mode.
Step 3cptone countrySelect the appropriate voice call progress tone 
for this interface. The default country for this 
command is us.
Step 4ring frequency (25  50)Select the ring frequency (in Hz) specific to 
the equipment attached to this voice port and 
appropriate to the country you are in.
Step 5description stringAttach descriptive text about this voice port 
connection.
Step 6comfort-noiseIf voice activity detection (VAD) is activated, 
specify that background noise is generated.
Step 7impedanceSpecify impedance, which is related to the 
electrical characteristics of the device that is 
plugged into a POTS port. Impedance is 
measured in ohms. 
						

							 
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For complete information on the dial peer commands, refer to the 
Cisco IOS Release 12.0
 documentation set. For general information on dial peer 
concepts, see Chapter 1, “Concepts.” 
Configuring Number Expansion
This section describes how to expand an extension number into a particular 
destination pattern. Use the following global configuration command to expand 
the extension number:
Router(config)# num-exp extension-number extension-string
To verify that you have mapped the telephone numbers correctly, enter the 
show num-exp command.
After you have configured dial peers and assigned destination patterns to them, 
enter the show dialplan number command to see how a telephone number maps 
to a dial peer. 
For complete information on the number expansion commands, refer to the 
Cisco IOS documentation set.
Configuration Example
This configuration shows voice traffic configured. You do not need to enter the 
commands marked “default.” These commands appear automatically in the 
configuration file that is generated when you use the show running-config 
command.
!
class-map voice
match access-group 101
!
policy-map mypolicy
class voice
priority 128
class class-default
fair-queue 16
!
ip subnet-zero
!
gateway
!
interface Ethernet0 
						

							 
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ip address 20.20.20.20 255.255.255.0
no ip directed-broadcast (default)
ip route-cache policy
ip policy route-map data
!
interface ATM0
ip address 10.10.10.20 255.255.255.0
no ip directed-broadcast (default)
no atm ilmi-keepalive (default)
pvc 1/40 
service-policy output mypolicy
protocol ip 10.10.10.36 broadcast
vbr-nrt 640 600 4
! 640 is the maximum upstream rate of ADSL
encapsulation aal5snap
!
bundle-enable
h323-gateway voip interface
h323-gateway voip id gk-twister ipaddr 172.17.1.1 1719
h323-gateway voip h323-id gw-820
h323-gateway voip tech-prefix 1#
!
router eigrp 100
network 10.0.0.0
network 20.0.0.0
!
ip classless (default)
no ip http server
!
access-list 101 permit ip any any precedence critical
route-map data permit 10
set ip precedence routine
!
!
line con 0
exec-timeout 0 0
transport input none
stopbits 1
line vty 0 4
login
!
!
voice-port 1
local-alerting
timeouts call-disconnect 0
!
voice-port 2
local-alerting 
						

							 
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!
voice-port 3
local-alerting
timeouts call-disconnect 0
!
voice-port 4
local-alerting
timeouts call-disconnect 0
!
dial-peer voice 10 voip
destination-pattern........
ip precedence 5
session target ras
!
dial-peer voice 1 pots
destination-pattern 5258111
port 1
!
dial-peer voice 2 pots
destination-pattern 5258222
port 2
!
dial-peer voice 3 pots
destination-pattern 5258333
port 3
!
dial-peer voice 4 pots
destination-pattern 5258444
port 4
!
end
Cisco 827 Router Configuration Examples
Examples are provided for the following configurations:
Cisco 827-4V Router Configuration
Cisco 827 Router Configuration
Corporate or Endpoint Router Configuration for Data Network
Corporate or Endpoint Router Configuration for Data and Voice Network 
						

							 
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Cisco 827 Router Configuration Examples
These configurations are intended to be examples only. Your router configuration 
may look different, depending on your network.
Cisco 827-4V Router Configuration 
The following is a configuration for the Cisco 827-4V router configured for 
H.323 signaling voice traffic. These commands appear automatically in the 
configuration file generated when you use the show running-config command.
ip subnet-zero
!
bridge crb
!
interface Ethernet0
no ip address
no ip directed-broadcast
bridge-group 1
!
interface ATM0
no ip address
no ip directed-broadcast
no atm ilmi-keepalive
bundle-enable
!
interface ATM0.1 point-to-point
ip address 1.0.0.1 255.255.255.0
no ip directed-broadcast
pvc voice 1/40 
protocol ip 1.0.0.2 broadcast
encapsulation aal5snap
!
!
interface ATM0.2 point-to-point
no ip address
no ip directed-broadcast
pvc data 1/41 
encapsulation aal5snap
!
bridge-group 1
!
ip classless
!
bridge 1 protocol ieee
!
voice-port 1
local-alerting 
						

							 
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!
voice-port 2
local-alerting
timeouts call-disconnect 0
!
voice-port 3
local-alerting
timeouts call-disconnect 0
!
voice-port 4
local-alerting
timeouts call-disconnect 0
!
dial-peer voice 101 pots
destination-pattern 14085271111
port 1
!
dial-peer voice 1100 voip
destination-pattern 12123451111
codec g711ulaw
session target ipv4:1.0.0.2
!
dial-peer voice 102 pots
destination-pattern 14085272222
port 2
!
dial-peer voice 1200 voip
destination-pattern 12123452222
codec g711ulaw
session target ipv4:1.0.0.2
!
dial-peer voice 103 pots
destination-pattern 14085273333
port 3
!
dial-peer voice 1300 voip
destination-pattern 12123453333
codec g711ulaw
session target ipv4:1.0.0.2
!
dial-peer voice 104 pots
destination-pattern 14085274444
port 4
!
dial-peer voice 1400 voip
destination-pattern 12123454444
codec g711ulaw