Cisco MC3810 Multiservice Access Concentrators

Document ID: 13998

Contents

Introduction
Prerequisites
      Requirements
      Components Used
      Conventions
      PRI Signaling for Cisco MC3810
CCS Cross Connect Example
CCS Frame Forwarding Example
Verify
Troubleshoot
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Related Information

Introduction

This document uses information already presented in the Common Channel Signaling (CCS) document on cisco.com, but it further presents the subject with other examples.

Prerequisites

Requirements

There are no specific requirements for this document.

Components Used

The information in this document is based on these software and hardware versions:

• Cisco MC3810 routers with T1 and digital voice modules (DVMs)

• WAN leased line

• Cisco IOS® Software version 12.0.2T and later

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.

Conventions

For more information on document conventions, refer to the Cisco Technical Tips Conventions.

PRI Signaling for Cisco MC3810

A PRI (which is the T1 connection on the Cisco MC3810s in the examples in this document) consists of 23B (bear) channels and 1D (signaling) channel for T1 signaling. In contrast to channel associated signaling (CAS), for CCS there is no standard on the information (A/B or A/B/C/D bit) for the status of a given channel.

The Cisco MC3810 supports Cross Connect or Frame Forward signaling for the D channel on the PRI. The Cisco MC3810 does not keep track of B channel activity, and as a result, the B channels are left in "nail-down" status; that is, connections over B channels are always established.

CCS Cross Connect Example

This topology shows an example of CCS cross connect.

In this example, the CCS channel from the PBX is cross-connected on the Cisco MC3810 to a timeslot on the T1/E1 controller. The channel is then passed through the wide area network (WAN) as a leased line to the second Cisco MC3810. The second MC3810 is cross connected to the digital voice module (DVM) signaling timeslot (timeslot 24 for T1, or timeslot 16 for E1). The channel is then passed to the second PBX. The CCS signal byte stream is passed through transparently by the Cisco MC3810.

• The wide area link must be a point-to-point full or fractional T1 or E1.

• Time-division multiplexing (TDM) cross connect Cisco MC3810s act transparently for the signaling channel; this is a bit-in, bit-out situation. In other words, there are no bits appended, and therefore, MC3810 supports the PBXs use of the non-HDLC-like signaling channel that is connected from the PBX to the MC3810 DVM.

• Multiple channels can be configured for a cross connect. There are PBXs in this topology, and they require more than one channel for signaling.

Here is the CCS cross connect configuration example, which works the same for both Cisco MC3810s in the CCS cross connect example topology above.

controller T1 0
linecode b8zs
framing esf
channel-group 1 timeslots 1-23 speed 64
tdm-group 1 timeslots 24
The tdm-group 1 timeslots 24 


!--- The command above assumes that channel 24 is the signaling channel. 
!--- Channel 24 on a standard PRI circuit, however, is reserved for signaling. 
!--- This is the same for the tdm-group 2 timeslots 24 command below. 


controller T1 1
linecode b8zs
framing esf
mode ccs cross-connect
tdm-group 2 timeslots 24


cross-connect t1 1 2 t1 0 1

The configuration set above states that the MC3810s pass every bit from the multiflex trunk module (MFT) to the DVM, and vice versa on channel 24. This allows the PBXs attached to both MC3810s to handshake over the D channel.

CCS Frame Forwarding Example

This topology shows an example of CCS frame forwarding:

In this example, the Cisco MC3810 captures the signaling frame from the PBX. The Cisco MC3810 then transports the signaling frame as a data frame through the Frame Relay or ATM network to the second Cisco MC3810. The second Cisco MC3810 then forwards the signaling frame to the PBX signaling channel.

• The signaling channel must be in HDLC format at 64Kbps.

• The WAN line can be HDLC (Point-to-Point T1/E1), Frame Relay, or ATM.

• These configurations are for the MC3810s in the CCS frame forwarding example topology above. The first configuration is for the MC3810 on the left of the topology, and the second configuration is for the MC3810 on the right side of the topology.

3810-dig-1

controller T1 0
 framing esf
 clock source internal
 linecode b8zs
 channel-group 1 timeslots 1-24 speed 64
!
controller T1 1
 framing esf
 linecode b8zs
 mode ccs frame-forwarding
 voice-group 0 timeslots 1-23 type ext-sig-master

3810-dig-2

controller T1 0
 framing esf
 clock source internal
 linecode b8zs
 channel-group 1 timeslots 1-24 speed 64
!
controller T1 1
 framing esf
 linecode b8zs
 mode ccs frame-forwarding
 voice-group 0 timeslots 1-23 type ext-sig-slave

There is no special requirement for a MC3810 to be designated as ext-sig-master or ext-sig-slave in the voice-group 0 timeslots 1-23 type command. A channel configured as ext-sig-master automatically generates the off-hook signal and stays in the off-hook state. A channel configured as ext-sig-slave automatically generates the answer signal when a call is terminated to that channel. These types of options are available only when the mode ccs cross-connect command is enabled.

Verify

In order to verify the functionality of frame forwarding, an alternate example with four connected routers is shown in this topology:

Routers 3800-ana-3 and 3800-ana-4 are configured to send data packets in HDLC format over channel 24 to the directly connected MC3810s. 3810-dig-1 and 3810-dig-2 are the routers that perform the frame forwarding in this situation. These configurations make it possible for 3810-ana-3 and 3810-ana-4 to communicate through the ATM frame relay cloud.

3810-ana-3

3810-ana-3#show running config
Building configuration...

controller T1 0
 framing esf
 linecode b8zs
 channel-group 1 timeslots 24 speed 64
!
interface Serial0:1
 ip address 1.1.1.1 255.255.255.0
 no ip directed-broadcast
 no fair-queue

!
end

3810-ana-4

3800-ana-4#show running config
Building configuration...

controller T1 0
framing esf
clock source internal
linecode b8zs
channel-group 1 timeslots 24 speed 64
!
interface Serial0:1
 ip address 1.1.1.2 255.255.255.0
 no ip directed-broadcast
 no fair-queue
!
end

Note: The configurations listed here are for 3810-dig-1 and 3810-dig-2, which perform frame forwarding:

3810-dig-2

3810-dig-2#show run
 
Current configuration:
!
frame-relay switching
!
!
controller T1 0
 framing esf
 linecode b8zs
 channel-group 1 timeslots 1-24 speed 64
!
controller T1 1
 framing esf
 linecode b8zs
 mode ccs frame-forwarding
 voice-group 1 timeslots 1-23 type ext-sig-master
!
!
interface Serial0:1
 ip address 20.20.20.2 255.255.255.252
 no ip directed-broadcast
 encapsulation frame-relay
 no ip route-cache
 no keepalive  
 cdp enable
 frame-relay traffic-shaping
 frame-relay map ip 20.20.20.1 100 broadcast
 frame-relay interface-dlci 100
  class tNt
  vofr cisco
 frame-relay intf-type dce
!
interface Serial1:23  


!--- The virtual Serial 1:23 interface above will be generated once CCS  
!--- frame forwarding mode is declared


 ip address 1.1.1.1 255.255.255.252
 no ip directed-broadcast
 no keepalive
 ccs connect Serial0:1 100  


!--- Direct data on signaling channel to be transmitted over DLCI 100 on interface 
!--- serial 0:1


!
!
map-class frame-relay tNt
 frame-relay voice bandwidth 256000
 frame-relay fragment 800
 no frame-relay adaptive-shaping
 frame-relay cir 768000
 frame-relay bc 2000
 frame-relay fair-queue
!
voice-port 1/1
 timeouts call-disconnect 0
 connection plar 101
!
voice-port 1/2
 timeouts call-disconnect 0
 connection plar 102
!
voice-port 1/3
 timeouts call-disconnect 0
 connection plar 103
!
voice-port 1/4
 timeouts call-disconnect 0
 connection plar 104
-snip-
voice-port 1/23
 timeouts call-disconnect 0
 connection plar 123
!
dial-peer voice 100 vofr
 no vad
 dtmf-relay
 destination-pattern 1..
 session target Serial0:1 100
end

The connection plar statement under each voice port is to be used to establish the nail-down connections for the B channels. The common practice is to have the connection plar commands configured on the MC3810 with the ext-sig-master command configured.

3810-dig-1

3810-dig-1
!
controller T1 0
 framing esf
 clock source internal
 linecode b8zs
 channel-group 1 timeslots 1-24 speed 64
!
controller T1 1
 framing esf
 linecode b8zs
 mode ccs frame-forwarding
 voice-group 0 timeslots 1-23 type ext-sig-slave
!
!
!
interface Serial0:1
 ip address 20.20.20.1 255.255.255.252
 no ip directed-broadcast
 encapsulation frame-relay
 no ip route-cache
 no keepalive
 cdp enable
 frame-relay traffic-shaping
 frame-relay interface-dlci 100
  class tNt
  vofr cisco
!
interface Serial1:23
 ip address 1.1.1.2 255.255.255.252
 no ip directed-broadcast
 no keepalive
 no fair-queue
 ccs connect Serial0:1 100
!
!
!
map-class frame-relay ff1
 frame-relay adaptive-shaping becn
 frame-relay cir 1544000
 frame-relay bc 1000
!
map-class frame-relay tNt
 frame-relay voice bandwidth 256000
 frame-relay fragment 800
 no frame-relay adaptive-shaping
 frame-relay cir 768000
 frame-relay bc 2000
 frame-relay fair-queue
!
-snip-
dial-peer voice 101 pots
 destination-pattern 101
 port 1/1
!
dial-peer voice 102 pots
 destination-pattern 102
 port 1/2
!
dial-peer voice 103 pots
 destination-pattern 103
 port 1/3
-snip-
!
dial-peer voice 123 pots
 destination-pattern 123
 port 1/23
end

Note: In the above command sequence, the dial-peer voice xxx pots commands are needed on this MC3810, as it terminates the calls from the other MC3810. It is also advisable to assign a unique private line, automatic ringdown (PLAR) ID for each channel to facilitate the troubleshooting process.

The frame forwarding configuration also applies to ATM. These are the configurations for ATM encapsulation and CCS frame forwarding:

3810-dig-1

3810-dig-1 
controller T1 0
framing esf
linecode b8zs
mode atm

controller T1 1
framing esf
linecode b8zs
mode ccs frame-forwarding
voice-group 1 timeslots 1-23 type ext-sig-master

interface Serial1:23
no ip address
no ip directed-broadcast
no keepalive
ccs connect ATM0 1 
no cdp enable


interface ATM0
no ip address
no ip directed-broadcast

interface ATM0.1 point-to-point
no ip directed-broadcast
atm pvc 1 0 44 aal5voice 384 384 100 oam 10


interface ATM0.4 point-to-point
ip address 1.1.1.2 255.255.255.0
no ip directed-broadcast
atm pvc 2 0 33 aal5snap 384 384 100 oam 10

3810-dig-2

controller T1 0
framing esf
linecode b8zs
mode atm


controller T1 1
framing esf
clock source internal
linecode b8zs
mode ccs frame-forwarding
voice-group 1 timeslots 1-23 type ext-sig-slave


interface Serial1:23
no ip address
no ip directed-broadcast
no ip route-cache
no keepalive
ccs connect ATM0 1
no cdp enable


interface ATM0.1 point-to-point
no ip directed-broadcast
atm pvc 1 0 44 aal5voice 384 384 100 oam 10

interface ATM0.4 point-to-point
ip address 1.1.1.1 255.255.255.0
no ip directed-broadcast
atm pvc 2 0 33 aal5snap 384 384 100 oam 10

There is no way to monitor the status of the D channel on any of these routers. It is, however, possible to see the status of the B channels. Issue the show voice call summary from the user EXEC mode. Here are some sample debug outputs from the show voice call summary command:

From MC3810 with Private Line Auto Ringdown (PLAR) Configured

1/1 (orig): eecm = ST_DIGIT_COLLECT,  LFXS= call_progress,  CPD= failure_cont
 
1/2 (orig): eecm = ST_DIGIT_COLLECT,  LFXS= call_progress,  CPD= failure_cont
 
-snip-


1/22 (orig): eecm = ST_ACTIVE,  LFXS= connected,  CPD= connected
 
1/23 (orig): eecm = ST_ACTIVE,  LFXS= connected,  CPD= connected

From MC3810 with dial-peer voice xxx pots Command Configured

/1 (  ): eecm = IDLE,  LFXO= idle,  CPD= idle
 
1/2 (  ): eecm = IDLE,  LFXO= idle,  CPD= idle
 
-snip-
 
1/22 (term): eecm = ST_ACTIVE,  LFXO= connected,  CPD= connected
 
1/23 (term): eecm = ST_ACTIVE,  LFXO= connected,  CPD= connected

Channel 1 and 2 in this situation still have not established the "nail-down" connection and these channels will try forever to establish a connection. Channel 22 and 23, however, have the connection established and are able to pass voice traffic.

To test the connectivity of the D channel from 3810-ana-4 to 3810-ana-3, ping 3810-ana-3's s0:1 interface with the ping command. You will see this:

3800-ana-4#ping 1.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 73/80/84 ms
3800-analog-4#

Troubleshoot

There is currently no specific troubleshooting information available for this configuration.

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Related Information

• Configuring MC3810 for TDM Cross Connect
• Voice Technology Support
• Voice and Unified Communications Product Support
• Recommended Reading: Troubleshooting Cisco IP Telephony
• Technical Support - Cisco Systems