Questions about Service Locator Points (SLP’s)

I was working with a customer last week on a few questions about SLP’s.  We needed to check what information is really returned by the SLP to the client.  It took a while to search for this information so I thought a post might be beneficial.  The SLP is used to help clients find a Management Point (MP).  The client will get information about an SLP from either AD or WINS,or it can be specified on the command line when the client is installed.  In order for clients to find the SLP in AD your site must be publishing the SLP to AD.  Workgroup clients on the other hand or not able to query AD to find the SLP so you must publish the SLP in WINS for them to be able to find it.  It is also important to know that the SLP is really only used during client installation or when a discovery is performed via the Config Manager Control Panel applet.  Information about what the SLP finds is found in the location services log file of the client.

When the client finds the SLP he sends an LDAP query to the SLP service running on the IIS server hosting the SLP.  You can run this same query by using the commands below in your IE Browser:

Find a Site:
https://<SLP Server Name>/sms_slp/slp.dll?site&ip=12.19.86.0

Find a Management Point (MP):
https://<SLP Server Name>/sms_slp/slp.dll?MP&ip=12.19.86.0

You will need to replace the ip= part with the IP Subnet that you are looking for.   Each of these can be added to the URL separated by '&'.

ad= <Active Directory site name>
ip= <IP Subnet>
ir= <IP Address>

When running the above in IE you should get back something like this:

The MP Query will return a list of the MP’s for the client:

This information can be very helpful when troubleshooting why a client can’t get policy or why the client is not finding a MP.  Most of the time it is a boundary related issue but it could also be an issue with the MP or with SQL.