Configuring Digital Voice Ports
Cisco provides digital T1 and E1 ports in the form of Voice and WAN Interface Cards (VWIC) for routers. These cards offer you the flexibility to configure them for a data connection or a voice connection. Unlike analog interfaces, you must configure digital interfaces before they will operate correctly, because the router does not know the type of network you will be using. As discussed in Chapter 7, "Gateway and Trunk Concepts," there are two types of voice network configurations you can use: T1/E1 channel associated signaling (CAS) or T1/E1 common channel signaling (CCS; commonly referred to as ISDN Primary Rate Interface [PRI]). The type of network to which you are connecting dictates the command you will use to configure your VWIC card: dsO-group for T1/E1 CAS connections or pri-group for T1/E1 CCS connections.
Example 8.5 demonstrates configuring all 24 channels of a T1 CAS interface to connect to a PSTN carrier.
Example 8.5 Configuring a T1 CAS PSTN Interface CME_Voice# show controllers t1 T1 1/0 is down.
Applique type is Channelized T1 Cablelength is long gain36 0db Transmitter is sending remote alarm. Receiver has loss of signal. alarm-trigger is not set Soaking time: 3, Clearance time: 10 AIS State:Clear LOS State:Clear LOF State:Clear Version info Firmware: 20050620, FPGA: 20, spm_count = 0 Framing is SF, Line Code is AMI, Clock Source is Line. Current port master clock:local osc on this network module Data in current interval (215 seconds elapsed): 0 Line Code Violations, 0 Path Code Violations 0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins 0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 215 Unavail Secs CME_Voice# configure terminal
Enter configuration commands, one per line. End with CNTL/Z. CME_Voice(config)# controller t1 1/0 CME_Voice(config-controller)# framing ? esf Extended Superframe sf Superframe
Example 8.5 Configuring a T1 CAS PSTN Interface continued
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CME_Voice(config-controller)# framing esf |
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CME_Voice(config-controller)# linecode ? |
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ami AMI encoding |
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b8zs B8ZS encoding |
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CME_Voice(config-controller)# linecode b8zs |
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CME_Voice(config-controller)# clock source ? |
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free-running Free Running Clock |
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internal Internal Clock |
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line Recovered Clock |
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CME_Voice(config-controller)# clock source line |
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CME_Voice(config-controller)# ds0-group ? |
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<0-23> Group Number |
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CME_Voice(config-controller)# ds0-group 1 ? |
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timeslots List of timeslots in the ds0-group |
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CME_Voice(config-controller)# ds0-group 1 timeslots |
? |
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<1-24> List of T1 timeslots |
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CME_Voice(config-controller)# ds0-group 1 timeslots |
1 |
-24 |
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type Specify the type of signaling |
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<cr> |
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CME_Voice(config-controller)# ds0-group 1 timeslots |
1 |
-24 |
type ? |
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e&m-delay-dial E & M Delay Dial |
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e&m-fgd E & M Type II FGD |
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e&m-immediate-start E & M Immediate Start |
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e&m-lmr E & M land mobil radio |
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e&m-wink-start E & M Wink Start |
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ext-sig External Signaling |
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fgd-eana FGD-EANA BOC side |
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fxo-ground-start FXO Ground Start |
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fxo-loop-start FXO Loop Start |
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fxs-ground-start FXS Ground Start |
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fxs-loop-start FXS Loop Start |
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none Null Signalling for External |
Call |
Control |
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<cr> |
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CME_Voice(config-controller)# ds0-group 1 timeslots |
1 |
-24 |
type fxo-loop-start ? |
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CME_Voice(config-controller)#~Z |
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CME_Voice# show voice port summary |
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IN OUT |
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PORT CH SIG-TYPE ADMIN OPER STATUS STATUS |
EC |
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|
1/0:1 01 fxo-ls up down idle on-hook |
y |
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|
0:1 |
02 |
fxo |
ls |
up |
down |
idle |
on |
hook |
y |
|
0:1 |
03 |
fxo |
ls |
up |
down |
idle |
on |
hook |
y |
|
0:1 |
04 |
fxo |
ls |
up |
down |
idle |
on |
hook |
y |
|
0:1 |
05 |
fxo |
ls |
up |
down |
idle |
on |
hook |
y |
|
0:1 |
06 |
fxo |
ls |
up |
down |
idle |
on |
hook |
y |
|
0:1 |
07 |
fxo |
ls |
up |
down |
idle |
on |
hook |
y |
|
0:1 |
08 |
fxo |
ls |
up |
down |
idle |
on |
hook |
y |
|
0:1 |
09 |
fxo |
ls |
up |
down |
idle |
on |
hook |
y |
|
0:1 |
10 |
fxo |
ls |
up |
down |
idle |
on |
hook |
y |
|
0:1 |
11 |
fxo |
ls |
up |
down |
idle |
on |
hook |
y |
|
0:1 |
12 |
fxo |
ls |
up |
down |
idle |
on |
hook |
y |
|
0:1 |
13 |
fxo |
ls |
up |
down |
idle |
on |
hook |
y |
|
0:1 |
14 |
fxo |
ls |
up |
down |
idle |
on |
hook |
y |
|
0:1 |
15 |
fxo |
ls |
up |
down |
idle |
on |
hook |
y |
|
0:1 |
16 |
fxo |
ls |
up |
down |
idle |
on |
hook |
y |
|
0:1 |
17 |
fxo |
ls |
up |
down |
idle |
on |
hook |
y |
|
0:1 |
18 |
fxo |
ls |
up |
down |
idle |
on |
hook |
y |
|
0:1 |
19 |
fxo |
ls |
up |
down |
idle |
on |
hook |
y |
|
0:1 |
20 |
fxo |
ls |
up |
down |
idle |
on |
hook |
y |
|
0:1 |
21 |
fxo |
ls |
up |
down |
idle |
on |
hook |
y |
|
0:1 |
22 |
fxo |
ls |
up |
down |
idle |
on |
hook |
y |
|
0:1 |
23 |
fxo |
ls |
up |
down |
idle |
on |
hook |
y |
|
0:1 |
24 |
fxo |
ls |
up |
down |
idle |
on |
hook |
y |
There are many commands to discuss from Example 8.5, starting with the show controllers t1 command. This command allows you to identify the T1 interfaces on your router. These interfaces do not appear in the show ip interface brief output, because the router does not know if you will configure the interface as a voice or data connection. Once you identify the slot and port of your T1 interface, you can then configure the necessary framing and linecode commands. These commands let you change how the T1 or E1 interface formats the frames it sends to the service provider. Set these values based on the service provider to which you are connecting.
Note If you are in the United States, most service providers use ESF framing and B8ZS linecoding.
After you have set the framing and linecoding, you can move into the clocking. The command clock source line instructs the router to receive its interface clocking from the service provider. If you are connecting to a PSTN carrier, this is the norm. If your router is connecting to a PBX system inside your company, you may enter the command clock source internal, which allows the router to provide clocking information to the PBX system.
Finally, the dsO-group command configures the line as a T1 CAS connection and allows you to enter the specific number of time slots you would like to provision. In Example 8.5, all 24 time slots were provisioned under DS0 group 1. The group number you choose can be any value from 0-23. This value acts as an identifier for the time slots you place into it. You could provision a single T1 line for many different purposes. For example, you could create DS0 group 5 with time slots 1-5 that connect to an onsite PBX system. You could then create DS0 group 6 using time slots 6-24 that connect to the PSTN (provided the PBX system and PSTN carrier were provisioned for these same time slot settings). Figure 8.3 illustrates the physical design of this network type.
PBX System
PBX System
- Figure 8.3 Provisioning Multiple Connections with a Single T1 Interface
Note The demultiplexing device shown in Figure 8.3 allows you to break the single T1 interface into multiple interfaces with specific channel assignments.
Notice that the dsO-group command also allows you to set the signaling type. This gives you the ability to connect to many different network types. The PSTN carrier typically uses FXO loop start signaling over the T1 CAS connection (this may differ depending on your location and service provider). PBX systems often support one of the various E&M signaling types.
Once you have entered the dsO-group command, the router automatically creates a voice port for each time slot you provision, as you can see from the show voice port summary output of Example 8.5. The port is listed as 1/0:1 because 1/0 represents the physical interface and the additional 1 represents the DS0 group number. You will want to make a note of this port identifier; you will need it when you configure the dial peers. Each of the ports listed represents a different channel on the T1 interface.
Configuring the digital T1/E1 interface for a CCS (ISDN PRI) PSTN connection uses similar syntax as the CAS. Example 8.6 demonstrates a configuration that provisions all 24 time slots of the VWIC interface as a PRI PSTN connection.
Example 8.6 Configuring a T1 CCS PSTN Interface
CME_Voice(config)# isdn switch-type ?
primary-4ess Lucent 4ESS switch type for the U.S. primary-5ess Lucent 5ESS switch type for the U.S. primary-dms100 Northern Telecom DMS-100 switch type for the U.S. primary-dpnss DPNSS switch type for Europe primary-net5 NET5 switch type for UK, Europe, Asia and Australia primary-ni National ISDN Switch type for the U.S.
primary-ntt NTT switch type for Japan primary-qsig QSIG switch type primary-ts014 TS014 switch type for Australia (obsolete) CME_Voice(config)# isdn switch-type primary-5ess
CME_Voice(config)# controller t1 1/0 CME_Voice(config-controller)# pri-group ?
nfas_d Specify the operation of the D-channel timeslot. service Specify the service type timeslots List of timeslots in the pri-group <cr>
CME_Voice(config-controller)# pri-group timeslots ? <1-24> List of timeslots which comprise the pri-group
CME_Voice(config-controller)# pri-group timeslots 1-24 ? nfas_d Specify the operation of the D-channel timeslot. service Specify the service type CME_Voice(config-controller)# pri-group timeslots 1-24 CME_Voice(config-controller)#"Z CME_Voice# show voice port summary
IN OUT
PORT CH SIG-TYPE ADMIN OPER STATUS STATUS EC
|
1/0 |
Od |
01 |
isdn |
voice |
up |
dorm |
none |
none |
y |
|
1/0 |
Od |
02 |
isdn |
voice |
up |
dorm |
none |
none |
y |
|
1/0 |
Od |
03 |
isdn |
voice |
up |
dorm |
none |
none |
y |
|
1/0 |
Od |
04 |
isdn |
voice |
up |
dorm |
none |
none |
y |
|
1/0 |
Od |
05 |
isdn |
voice |
up |
dorm |
none |
none |
y |
|
1/0 |
Od |
06 |
isdn |
voice |
up |
dorm |
none |
none |
y |
|
1/0 |
Od |
07 |
isdn |
voice |
up |
dorm |
none |
none |
y |
|
1/0 |
Od |
08 |
isdn |
voice |
up |
dorm |
none |
none |
y |
|
1/0 |
Od |
09 |
isdn |
voice |
up |
dorm |
none |
none |
y |
|
1/0 |
Od |
10 |
isdn |
voice |
up |
dorm |
none |
none |
y |
|
1/0 |
Od |
11 |
isdn |
voice |
up |
dorm |
none |
none |
y |
Example 8.6 Configuring a T1 CCS PSTN Interface continued
|
1/0 |
Od |
12 |
isdn |
voice |
up |
dorm |
none |
none |
y |
|
1/0 |
Od |
13 |
isdn |
voice |
up |
dorm |
none |
none |
y |
|
1/0 |
Od |
14 |
isdn |
voice |
up |
dorm |
none |
none |
y |
|
1/0 |
Od |
15 |
isdn |
voice |
up |
dorm |
none |
none |
y |
|
1/0 |
Od |
16 |
isdn |
voice |
up |
dorm |
none |
none |
y |
|
1/0 |
Od |
17 |
isdn |
voice |
up |
dorm |
none |
none |
y |
|
1/0 |
Od |
18 |
isdn |
voice |
up |
dorm |
none |
none |
y |
|
1/0 |
Od |
19 |
isdn |
voice |
up |
dorm |
none |
none |
y |
|
1/0 |
Od |
20 |
isdn |
voice |
up |
dorm |
none |
none |
y |
|
1/0 |
Od |
21 |
isdn |
voice |
up |
dorm |
none |
none |
y |
|
1/0 |
Od |
22 |
isdn |
voice |
up |
dorm |
none |
none |
y |
|
1/0 |
Od |
23 |
isdn |
voice |
up |
dorm |
none |
none |
y |
When configuring this CCS connection, the first step is to set the ISDN switch type. This needs to match the type of switch your local service provider is using. Example 8.6 sets this to primary-5ess. Once you have configured the switch type, the router will allow you to enter the pri-group command. This works identically to the dsO-group command in that it allows you to provision a specific number of time slots for use with the PSTN carrier. This command does not allow you to select a signaling type because the router assumes ISDN PRI signaling.
Once you have entered this command, the router creates 24 ISDN voice ports, verified with the show voice port summary command, which it will use for incoming and outgoing voice calls. Notice that the voice port is represented by the identifier 1/0:23. This represents channel 23 (time slot 24) of the T1 ISDN PRI connection (channels are listed from 0-23, whereas time slots are listed 1-24). This is the dedicated signaling channel used to bring up the other 23 voice bearer channels.
'Key Topic
As before, you will want to make note of this port identifier for the ISDN circuit. The router will require you to identify this interface when configuring your dial peers.
Continue reading here: Voice Call Legs
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