OK, a tale of two diagnostic logs. For reference, 10.15.16.220 is the machine that runs SiriusStreams, 10.15.16.225 is the media center box.
Successfully playing channel 1 from my Media Center:
And here's the failed attempt to play Channel 1 from the extender
Successfully playing channel 1 from my Media Center:
1:13 AM: Servicing request from '10.15.16.225:1137'...
1:13 AM: Processing GET request: GET /sirius?channel=1&format=asx HTTP/1.1
Accept: */*
User-Agent: NSPlayer/11.0.5721.5251
Host: 10.15.16.220
X-Accept-Authentication: Negotiate, NTLM, Digest, Basic
Pragma: version11-enabled=1
Pragma: no-cache,rate=1.000,stream-time=0,stream-offset=0:0,packet-num=4294967295,max-duration=0
Pragma: packet-pair-experiment=1
Pragma: pipeline-experiment=1
Supported: com.microsoft.wm.srvppair, com.microsoft.wm.sswitch, com.microsoft.wm.predstrm, com.microsoft.wm.startupprofile
Pragma: xClientGUID={3300AD50-2C39-46c0-AE0A-47C698C88A2C}
Accept-Language: en-US, *;q=0.1
1:13 AM: Retrieving MMS URL for channel 'Sirius 1 - SIRIUS XM Hits 1'...
1:13 AM: Redirecting to mms stream...
1:13 AM: Completed request from '10.15.16.225:1137'.
And here's the failed attempt to play Channel 1 from the extender
1:15 AM: Servicing request from '10.15.16.225:1158'...
1:15 AM: Processing GET request: GET /sirius?channel=1&format=asx HTTP/1.1
Connection: Close
Host: 10.15.16.220:51710
1:15 AM: Retrieving MMS URL for channel 'Sirius 1 - SIRIUS XM Hits 1'...
1:15 AM: Retrieving ASX for channel 'Sirius 1 - SIRIUS XM Hits 1'...
1:15 AM: Sending asx data...
1:15 AM: Completed request from '10.15.16.225:1158'.
1:15 AM: Servicing request from '10.15.16.225:1159'...
1:15 AM: Processing GET request: GET /sirius?channel=1&format=asx HTTP/1.1
Connection: Close
Host: 10.15.16.220:51710
1:15 AM: Retrieving MMS URL for channel 'Sirius 1 - SIRIUS XM Hits 1'...
1:15 AM: Retrieving ASX for channel 'Sirius 1 - SIRIUS XM Hits 1'...
1:15 AM: Sending asx data...
1:15 AM: Completed request from '10.15.16.225:1159'.