WSUS

I have WSUS server in my office for windows patch management. My
Domain controller is not getting displayed in the WSUS server.

DC – ismartblr1 OS : win2k3 domain : llspl
WSUS : ismartblr-wsus OS – win2k3

Wsus server is joined in llspl domain. I have already configured GPO, all
my other workstation in this domain is displayed in WSUS.

Is there any way i Can my DC into WSUS manually or automatically. Kindly
help.