Asterisk phone cisco iad2420

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The Cisco IAD2420 is a family of devices that speak MGCP. Generally they are used to connect via a WAN interface to a call concentrator and deliver their voice channels in the form of analog lines or a T-1 for connection into a PBX.

In my case this is a Cisco IAD2421 with 16 analog channels on an Amphenol connector. Below is the information from my router:

iad2421#sh ver
Cisco Internetwork Operating System Software
IOS (tm) IAD2420 Software (C2420-A2I8K8SV5-M), Version 12.2(4)T1,  RELEASE SOFTWARE (fc1)
TAC Support: http://www.cisco.com/tac
Copyright (c) 1986-2001 by cisco Systems, Inc.
Compiled Thu 25-Oct-01 20:32 by ccai
Image text-base: 0x00023000, data-base: 0x00F1213C

ROM: System Bootstrap, Version 12.1(5r)XR1, RELEASE SOFTWARE (fc1)
ROM: IAD2420 Software (IAD2420-WBOOT-M), Version 12.1(1.0.4), CISCO DEVELOPMENT TEST VERSION

iad2421 uptime is 2 hours, 32 minutes
System returned to ROM by reload
System restarted at 19:00:00 EST Sun Feb 28 1993
System image file is "flash:c2420-a2i8k8sv5-mz.122-4.T1.bin"

Cisco IAD2420 (MPC860P) processor (revision 240.05) with 57344K/8192K bytes of memory.
Processor board ID REDACTED
PPC860 PowerQUICC, partnum 0x0005, version X02(0x0002)
Channelized E1, Version 1.0.
Bridging software.
Primary Rate ISDN software, Version 1.1.
IAD2420 SCB board (v01.A0), FPGA version 0.6
1 Multiflex T1(slot 3) RJ45 interface(v03.A0)
1 Sixteen FXS Analog Voice Module (v01.B0)
1 High Density Analog Power Module (v01.A0)
1 4-DSP(slot2) High Performance Compression Module(v01.A0)
1 Ethernet/IEEE 802.3 interface(s)
1 Serial network interface(s)
1 Serial(sync/async) network interface(s)
1 terminal line(s)
1 Channelized T1/PRI port(s)
256K bytes of non-volatile configuration memory.
32768K bytes of processor board System flash (INTEL28F640)

Configuration register is 0x3824

I am using the included ethernet connection to speak with Asterisk and the T-1 WIC is unused. Note that this is a fully capable router and was commonly used to provide both VoIP as well as internet services for a small business.

DISCLAIMER: Documentation on Cisco's site is sparse, and growing sparser. This hardware is no longer supported officially. What is here Works For Me (TM) but many of these options I'm not 100% clear as to their function. YMMV.

Below are snips from the IAD2421's configuration:

iad2421#sh run
Building configuration...

Current configuration : 3817 bytes
 ! No configuration change since last restart
version 12.2
 ! ...
no voice confirmation-tone
voice-card 0
 ! ...
interface Ethernet0
 ip address
 no ip route-cache
 no ip mroute-cache
 no cdp enable
 ! ...
voice-port 1/1
 codec g711ulaw
 caller-id format e911
voice-port 1/2
 codec g711ulaw
 caller-id format e911
voice-port 1/3
 codec g711ulaw
 caller-id format e911
 ! ... this continues through voice-port 1/16, rest snipped
mgcp call-agent service-type mgcp version 1.0
mgcp dtmf-relay voip codec all mode out-of-band
mgcp modem passthrough voip mode ca
mgcp tse payload 100
no mgcp timer receive-rtcp
mgcp profile default
dial-peer cor custom
dial-peer voice 201 voip
 application mgcpapp
 answer-address 201
 signal-type ext-signal
dial-peer voice 1 pots
 application mgcpapp
 port 1/1
dial-peer voice 2 pots
 application mgcpapp
 port 1/2
dial-peer voice 3 pots
 application mgcpapp
 port 1/3
 ! ... this continues through dial-peer voice 16 pots, rest snipped

And here is my mgcp.conf:

; MGCP Configuration for Asterisk
port = 2727
bindaddr =
disallow = all
allow = ulaw
allow = alaw

host =
context = internal
canreinvite = no
threewaycalling = yes
cancallforward = yes
transfer = yes
callwaiting = yes
wcardep = *
slowsequence = yes
line => aaln/S1/16
line => aaln/S1/15
line => aaln/S1/14
line => aaln/S1/13
line => aaln/S1/12
line => aaln/S1/11
line => aaln/S1/10
line => aaln/S1/9
line => aaln/S1/8
line => aaln/S1/7
line => aaln/S1/6
line => aaln/S1/5
line => aaln/S1/4
line => aaln/S1/3
line => aaln/S1/2
line => aaln/S1/1

Of special note are the following options and their needs:
slowsequence = yes
Without this, the CRCX and RQNT packets from Asterisk come before the channel is fully "up". In this case the IAD will return "400 <seqno> Endpt in transient state." and the user will hear congestion. ***See note about patch below***

canreinvite = no
Without this, when an MGCP channel calls another MGCP channel and they are natively bridged, the hangup request is never sent to Asterisk and the channels are not reset until the phone goes off-hook and back on again ***See note about patch below***

wcardep = *
Without this messages will be logged to the Asterisk console along the lines of "gateway iad2421 does not exist"

Also take note of the S1 in aaln/S1/1. It is slightly different from other MGCP channel names.

      • Patch Note ***
I have submitted a patch which enhances the reliability of the IAD2421 when used with Asterisk. Read about it at
Asterisk Bug ID 0002982
A patch is included. This bug can be triggered or made more critical by misconfiguration as noted above.
Created by: bklang, Last modification: Sun 13 of May, 2012 (20:50 UTC) by admin
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