external cfg:
<settings>
        <param name='dialplan' value='XML'/>
        <param name='user-agent-string' value='NP000'/>
        <param name='username' value='NP000' />
        <param name='ext-sip-ip' value='auto'/>
        <param name='ext-rtp-ip' value='auto'/>
        <param name='rtp-ip' value='auto'/>
        <param name='sip-ip' value='auto'/>
        <param name='sip-port' value='5060'/>
        <param name='nonce-ttl' value='60'/>
        <param name='rtp-timeout-sec' value='300'/>
        <param name='rtp-hold-timeout-sec' value='1800'/>
        <param name='rtp-timer-name' value='soft'/>
        <param name='aggressive-nat-detection' value='True'/>
        <param name='NDLB-received-in-nat-reg-contact' value='False'/>

        <param name='NDLB-broken-auth-hash' value='False'/>
        <param name='enable-timer' value='True'/>
        <param name='session-timeout' value='1800'/>
        <param name='apply-nat-acl' value='rfc1918'/>
        <param name='inbound-codec-prefs' value='PCMA,PCMU,G729'/>
        <param name='outbound-codec-prefs' value='PCMA,PCMU,G729'/>
        <param name='inbound-codec-negotiation' value='greedy'/>
        <param name='disable-transcoding' value='True'/>
        <param name='debug' value='0'/>
        <param name='rfc2833-pt' value='101'/>
        <param name='dtmf-duration' value='100'/>
        <param name='disable-register' value='False'/>
        <param name='challenge-realm' value='auto_from'/>
        <param name='auth-calls' value='True'/>
        <param name='log-auth-failures' value='True'/>
        <param name='context' value='public'/>
        <param name='apply-inbound-acl' value='domains'/>
	<!--<param name='inbound-late-negotiation' value='true'/>-->

        <param name="pass-rfc2833" value="true"/>
        <param name='pass-callee-id' value='true'/>
        <param name='manage-presence' value='false'/>
      </settings>

-- 
[Joaquin Peral Cascales]
Departamento de Telefonía
911090048