Manual:$wgShowIPinHeader

Users: $wgShowIPinHeader
Show the IP in the user bar for anonymous users.
Introduced in version:	pre 1.1.0
Removed in version:	still in use
Allowed values:	(boolean)
Default value:	true

Other settings: Alphabetical | By Function

Details

Show personal tool links (links to user page and user talk page) for anonymous visitors ("IPs"). Disabling this allows for improved caching, because all anonymous visitors can then be served the exact same version of each page.

Note: If $wgUseFileCache is enabled, $wgShowIPinHeader is automatically set to false.