intermittent fax issue

Unanswered Question
Nov 16th, 2009
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I have a 2811 router with 1 primary rate and 1 fxs interface. On the fxs interface i have a fax machine. The fax call comes in over the pri and is sent to the fxs interface. Unfortunately there are a lot of failures with the inbound faxes. Even from the same numbers. About 4/10 fail.

Now when running the debug isdn q931 and voip ccapi the only thing i can see is that vad is on for the inbound fax call and as the fax is on a pots interface can this make a difference? Can i rectify by adding a generic voip interface with no vad even though this is an inbound fax and inbound dial-peer is 1 and outbound is 2?

Anything i can try to resolve?


isdn switch-type primary-net5


voice-card 0

no dspfarm


password encryption aes


voice call send-alert

voice rtp send-recv


voice service pots


voice service voip

allow-connections h323 to h323





voice class codec 1

codec preference 1 g711ulaw

codec preference 2 g729r8




voice class h323 1

h225 timeout tcp establish 3

isdn switch-type primary-net5

isdn incoming-voice voice

isdn map address 1* plan unknown type unknown

isdn sending-complete

voice-port 0/3/0:15


voice-port 0/2/0

ring cadence pattern04

input gain -6

cptone NZ

impedance complex1


voice-port 0/2/1

ring cadence pattern04

cptone NZ

dial-peer voice 1 pots

description Incoming POTS Dial Peer

incoming called-number .


port 0/3/0:15

forward-digits all

dial-peer voice 2 pots

description Branch Fax

destination-pattern 1234

port 0/2/0

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paolo bevilacqua Mon, 11/16/2009 - 04:00
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This is a FAQ

Please configure:

network-clock-select 1 e1 0/3/0:15

And report again.

clougher01 Mon, 11/16/2009 - 10:06
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Yes i already have that assigned just didnt put it in the config sample.

network-clock-participate wic 3

network-clock-select 1 E1 0/3/0

gsidhu Mon, 02/20/2012 - 22:06
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I have come across a very similar issue. Please could you let me know how this issue got resolved.



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