asterisk users - May 2010 - 1.6.2.8: need sip reload to reach peers.

Running 1.6.2.8 and using teliax and junction for sip providers. We also 
  have an internal sip network for extensions. On boot both providers 
are shown as unspecified and UNKNOWN. The internal sip extensions are 
found. sip reload always finds the providers.

Why doesn't asterisk find the providers when it starts up? And if it 
doesn't find them, how long before it tries again?

sean