Recipe 11.10 Modifying the Cost for a Site Link

11.10.1 Problem

You want to modify the cost for a site link.

11.10.2 Solution

11.10.2.1 Using a graphical user interface

Open the Active Directory Sites and Services snap-in.
In the left pane, expand Sites Inter-Site Transports.
Click either the IP or SMTP folder depending where the site link is stored.
In the right pane, double-click on the link you want to modify.
Under the General tab, you can change the cost for the site link.
Click OK.

11.10.2.2 Using a command-line interface

Create an LDIF file called modify_site_link_cost.ldf with the following contents. Replace <LinkName> with the name of the site you want to modify.

dn: cn=DEFAULTIPSITELINK,cn=IP,cn=inter-site 
transports,cn=sites,cn=configuration,<ForestRootDN>
changetype: modify
replace: cost
cost: <LinkCost>
-

Then run the following command:

> ldifde -v -i -f modify_site_link_cost.ldf

11.10.2.3 Using VBScript

' This code modifies the cost attribute of a site link
' ------ SCRIPT CONFIGURATION ------
strLink = "<SiteLink>"   ' e.g. DEFAULTIPSITELINK
intCost = <LinkCost>     ' e.g. 200
' ------ END CONFIGURATION ---------

set objRootDSE = GetObject("LDAP://RootDSE")
set objLink = GetObject("LDAP://cn=" & strLink & _
                        ",cn=IP,cn=Inter-site Transports,cn=sites," & _
                        objRootDSE.Get("configurationNamingContext") )
objLink.Put "cost", intCost
objLink.SetInfo

WScript.Echo "Successfully modified link: " & strLink

11.10.3 Discussion

The cost attribute is one of the most important attributes of siteLink objects. cost is used by the KCC to determine what connection objects should be created to allow domain controllers to replicate data.

cost is inversely proportional to bandwidth. The lower the cost, the greater the bandwidth. The number you use for the cost is also arbitrary; the default is 100. You could use 100-1,000 as the range for your site link costs, or you could use 1-10. The actual number isn't important, it is relative based on the other site links.