/mcpand delay. In addition, this command automatically enables a Cisco IOS feature called packet loss concealment whereby lost scan lines are repeated to spoof the fax machine to believe that it has received all the data. Note that, while ECM can improve the success rate of fax transmissions in lossy VoX networks, the basic network problems remain and are to be addressed prior to the occurrence of other problems. A straightforward configuration step performed under the VoIP dial-peer is to disable ECM. As noted in the command reference, this command currently works only for VoIP dial-peers. It can be configurable for VoFR and VoATM, but it does not disable ECM. fax-relay ECM disable Command
<#root> vnt-3660-23(config-dial-peer)# fax-relay ECM ? disable Disables ECM mode for fax relay
fax NSF Command The fax NSF command is used to prevent the transfer of proprietary fax capabilities. Because the fax relay implementation of the router demodulates and decodes the fax tones based on the T.30 specification, transactions or encoding that are proprietary break fax relay and cause the fax transmission to fail. Certain brands of fax machines use these proprietary encodings to signal the the availability of enhanced capabilities, which help a fax manufacturer distinguish its products from others. This capability notification takes place with the optional Non Standard Facilities (NSF) field within fax negotiation. When you issue the fax NSF command, the router overwrites the NSF, so only standard fax transactions occurs. Vendor-specific facilities that are beyond the standard Group 3 requirements, and that break Cisco fax relay, is not usable. Usually the NSF is set to all zeros when this command is issued, and this fixes problems caused by the NSF field. fax NSF Command
<#root> vnt-3660-23(config-dial-peer)# fax NSF ? WORD Two-digit country code + four-digit manufacturer code vnt-3660-23(config-dial-peer)# fax NSF 000000