yum update not working from spacewalk server

I have registered an SLES11SP1 server with my spacewalk server however when I perform a ‘yum repolist’, I do not see my spacewalk server as one of the available repositories. So when I perform yum update (any-package), it does not find an update available. HOwever within the Spacewalk GUI it can see that 23 packages have updates available. Can anyone shed some light on this?