nat=no не помогло, по крайней мере sip show peer опять отображал Nat : RFC3581. Помогло nat=never - sh peer ... дает nat: no.
Поведение не изменилось t38 * проключает через себя.

Уточните, какая версия 1.6? Были отличия в поведении 1.6.0.9 и 1.6.1.1
Как-то надо SIP debug удостовериться, что Cisco на t.38 реинвайт даёт акцепт и MP202 тоже не против.

asterisk*CLI>
PBX Core settings
-----------------
Version: 1.6.0.9
Build Options: LOADABLE_MODULES
Maximum calls: Not set
Maximum open file handles: Not set
Verbosity: 1
Debug level: 0
Maximum load average: 0.000000
Minimum free memory: 0 MB
Startup time: 22:43:25
Last reload time: 22:43:25
System: Linux/2.6.18-92.el5 built by root on i686 2009-05-06 20:16:30 UTC
System name:
Default language: en
Language prefix: Enabled
User name and group: /
Executable includes: Disabled
Transcode via SLIN: Enabled
Internal timing: Disabled
Transmit silence during rec: Disabled

T.38 реинвайт * не выдает

а должен бы!
Надо переходить на 1.6.1.1
Есть положительные отзывы именно в этом вопросе. Мы сами внедрили недавно hylafax + t38 modem + AvantFax именно на 1.6.1.1
Правда там схема Asterisk <=> Cisco AS5350

мде... Значит видимо баг :)
спасибо

О, то есть оно работает-таки?
А версии spandsp/pwlib/opal ?

bird_of_Luck, хочешь пришлю полученый в мыло ПДФ-факс о 45-ти страницах?
О как!
Детали - в личку на asteriskforum.ru

Протестил 1.6.1.1 - изменения есть - t.38 проключается напрямую. Но все равно * горбатого лепит:

<--- SIP read from UDP://172.17.9.203:5060 --->
INVITE sip:97377536@172.17.9.52 SIP/2.0
From: "ac-backoffice-fax"<sip:ac-backoffice-fax@172.17.9.203>;tag=10191de8-cb0911ac-13c4-45028-289-747282bc-289
To: "97377536"<sip:97377536@172.17.9.52>;tag=as2dd53cb9
Call-ID: 1019c208-cb0911ac-13c4-45028-289-6298ff3e-289
CSeq: 3 INVITE
Via: SIP/2.0/UDP 172.17.9.203:5060;branch=z9hG4bK-2a9-a66be-35d4698b
Max-Forwards: 70
Supported: replaces,100rel
User-Agent: MP202/2.6.0_build_2
Contact: <sip:ac-backoffice-fax@172.17.9.203:5060>
Authorization: Digest username="ac-backoffice-fax",realm="asterisk",nonce="2f20c585",uri="sip:97377536@172.17.9.52",response="91cb4a5312c4b5f3847d4c3d87442563
",algorithm=MD5
Content-Type: application/sdp
Content-Length: 289

v=0
o=ac-backoffice-fax 1247812730 1247812731 IN IP4 172.17.9.203
s=-
c=IN IP4 172.17.9.203
t=0 0
m=image 5004 udptl t38
a=T38FaxVersion:0
a=T38FaxMaxBuffer:1024
a=T38FaxMaxDatagram:122
a=T38FaxRateManagement:transferredTCF
a=T38FaxUdpEC:t38UDPRedundancy
a=T38MaxBitRate:14400

<--- Transmitting (no NAT) to 172.17.9.203:5060 --->
SIP/2.0 100 Trying
Via: SIP/2.0/UDP 172.17.9.203:5060;branch=z9hG4bK-2a9-a66be-35d4698b;received=172.17.9.203
From: "ac-backoffice-fax"<sip:ac-backoffice-fax@172.17.9.203>;tag=10191de8-cb0911ac-13c4-45028-289-747282bc-289
To: "97377536"<sip:97377536@172.17.9.52>;tag=as2dd53cb9
Call-ID: 1019c208-cb0911ac-13c4-45028-289-6298ff3e-289
CSeq: 3 INVITE
Server: Asterisk PBX 1.6.1.1
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY
Supported: replaces, timer
Contact: <sip:97377536@172.17.9.52>
Content-Length: 0

[Jul 17 10:31:12] VERBOSE[26521] chan_sip.c: Reliably Transmitting (no NAT) to 172.17.9.254:5060:
INVITE sip:7377536@172.17.9.254:5060 SIP/2.0
Via: SIP/2.0/UDP 172.17.9.52:5060;branch=z9hG4bK3dd1f222;rport
Max-Forwards: 70
From: "ac-backoffice-fax" <sip:ac-backoffice-fax@172.17.9.52>;tag=as5e057dd3
To: <sip:7377536@172.17.9.254>;tag=23098A94-A62
Contact: <sip:ac-backoffice-fax@172.17.9.52>
Call-ID: 29cf0fdc351d31786aaf9a201b222927@172.17.9.52
CSeq: 103 INVITE
User-Agent: Asterisk PBX 1.6.1.1
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY
Supported: replaces, timer
X-asterisk-Info: SIP re-invite (External RTP bridge)
Content-Type: application/sdp
Content-Length: 284

v=0
o=root 103187934 103187935 IN IP4 172.17.9.203
s=Asterisk PBX 1.6.1.1
c=IN IP4 172.17.9.203
t=0 0
m=image 4122 udptl t38
a=T38FaxVersion:0
a=T38MaxBitRate:9600
a=T38FaxRateManagement:transferredTCF
a=T38FaxMaxBuffer:400
a=T38FaxMaxDatagram:400
a=T38FaxUdpEC:t38UDPFEC

<--- SIP read from UDP://172.17.9.254:5060 --->
SIP/2.0 200 OK
Via: SIP/2.0/UDP 172.17.9.52:5060;branch=z9hG4bK3dd1f222;rport
From: "ac-backoffice-fax" <sip:ac-backoffice-fax@172.17.9.52>;tag=as5e057dd3
To: <sip:7377536@172.17.9.254>;tag=23098A94-A62
Date: Fri, 17 Jul 2009 06:31:12 GMT
Call-ID: 29cf0fdc351d31786aaf9a201b222927@172.17.9.52
Server: Cisco-SIPGateway/IOS-12.x
CSeq: 103 INVITE
Allow: INVITE, OPTIONS, BYE, CANCEL, ACK, PRACK, COMET, REFER, SUBSCRIBE, NOTIFY, INFO, UPDATE, REGISTER
Allow-Events: telephone-event
Contact: <sip:7377536@172.17.9.254:5060>
Content-Type: application/sdp
Content-Length: 284

v=0
o=CiscoSystemsSIP-GW-UserAgent 8245 6798 IN IP4 172.17.9.254
s=SIP Call
c=IN IP4 172.17.9.254
t=0 0
m=image 18556 udptl t38
c=IN IP4 172.17.9.254
a=T38FaxVersion:0
a=T38MaxBitRate:9600
a=T38FaxRateManagement:transferredTCF
a=T38FaxMaxBuffer:200
a=T38FaxMaxDatagram:72

<--- Reliably Transmitting (no NAT) to 172.17.9.203:5060 --->
SIP/2.0 200 OK
Via: SIP/2.0/UDP 172.17.9.203:5060;branch=z9hG4bK-2a9-a66be-35d4698b;received=172.17.9.203
From: "ac-backoffice-fax"<sip:ac-backoffice-fax@172.17.9.203>;tag=10191de8-cb0911ac-13c4-45028-289-747282bc-289
To: "97377536"<sip:97377536@172.17.9.52>;tag=as2dd53cb9
Call-ID: 1019c208-cb0911ac-13c4-45028-289-6298ff3e-289
CSeq: 3 INVITE
Server: Asterisk PBX 1.6.1.1
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY
Supported: replaces, timer
Contact: <sip:97377536@172.17.9.52>
Content-Type: application/sdp
Content-Length: 293

v=0
o=root 1485912679 1485912681 IN IP4 172.17.9.254
s=Asterisk PBX 1.6.1.1
c=IN IP4 172.17.9.254
t=0 0
m=image 4438 udptl t38
a=T38FaxVersion:0
a=T38MaxBitRate:9600
a=T38FaxRateManagement:transferredTCF
a=T38FaxMaxBuffer:122
a=T38FaxMaxDatagram:122
a=T38FaxUdpEC:t38UDPRedundancy

Здесь .203 codes .254 cisco. Почему в инвайте к циске были изменены параметры:
a=T38FaxUdpEC:t38UDPRedundancy
a=T38MaxBitRate:14400
на
a=T38FaxUdpEC:t38UDPFEC
a=T38MaxBitRate:9600

Потом циска отвечает
a=T38FaxMaxDatagram:72

а codes d 200 OK получает
a=T38FaxMaxDatagram:122

забавно

Кому нибудь удалось передать рабочую конфигурацию t38 passthrough?