; The Call to extension 601

[Dec 16 14:02:02] WARNING[94761]: chan_sip.c:8274 check_auth: username mismatch, have <600>, digest has <2000>
[Dec 16 14:02:02] NOTICE[94761]: chan_sip.c:13596 handle_request_invite: Failed to authenticate user "Desk" <sip:600@10.0.1.6>;tag=f4qaruu4ey

; The relevant portion of the dialplan

[from-sip-internal]
exten => 600,1,Dial(SIP/600)

exten => 601,1,Dial(SIP/601)