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Cisco ATA 186 and Cisco ATA 188 Analog Telephone Adaptor Administrator’s Guide (SCCP)
Ol-3141-01
Chapter 6 Configuring and Debugging Fax Services
Debugging the Cisco ATA 186/188 Fax Services
Possible Cause for Failure
• Cisco fax relay option is not disabled on the gateway.
Example 6-10 Fax Pass-through Mode Failure
---------- FAX Summary 1 ----------
[ 33]<3.200=>2.53> Codec G729
[ 39]<2.53=>3.200> Codec G729
[ 562]<2.53=>3.200> NTE PT 101, EVT 34: Modem Mode, ANSam tone Detected (RFC2833)
[ 563]<2.53=>3.200> NTE PT 101, EVT 34: Modem Mode, ANSam tone Detected (RFC2833)
[ 565]<2.53=>3.200> NTE PT 101, EVT 34: Modem Mode, ANSam tone Detected (RFC2833)
[ 566]<2.53=>3.200> Codec G711u/D
[ 568]<2.53=>3.200> NTE PT 101, EVT 34: Modem Mode, ANSam tone Detected (RFC2833)
[ 580]<3.200=>2.53> Codec G711u/D
Analysis
• <3.200> is the originating Cisco ATA, and <2.53> is the terminating gateway.
• Both sides initially use G.729.
• <2.53> gateway sends NTE signaling packets, then upspeeds to G.711µ-law.
• <3.200>The Cisco ATA switches to G.711µ-law also, but never sends NTE signaling packets.
• Fax transmission fails because <2.53> gateway does not receive any NTE packets, and it drops the
fax call.
Possible Cause for Failure
• The Cisco ATA does not support the NTE signaling method and requires that the gateways use the
NSE signaling method.
rtpcatch Limitations
• rtpcatch performs optimally when analyzing capture files containing only one VoIP session.
• rtpcatch detects only G.711A, G.711µ-law, G.723, G.729, T.38, Cisco fax relay, modem
pass-through with or without redundancy packets, RTCP packets and NSE packets.
• rtpcatch can handle a maximum of 20 prserv ports using the -port option.
• rtpcatch may not detect T.38 packets correctly.
