Syntax: one or more domain names separated by space or line break
Allow walk to fetch pages from any host in the specified domain(s). Any URL (of any protocol) with a hostname ending in any of the specified domains will be accepted.
E.g. given Base URLs of http://www.example.com/ and Extra Domains othersite.com, the Search Appliance will walk all of www.example.com, as well as any URLs referring to any machine in othersite.com or its sub-domains (e.g. docs.othersite.com).
This option is not a "restricter" but an "enabler". All hosts specified will be walked and any others that match the given domain(s) will also be walked.
Note: This option does not direct the walk to web servers in the specified domains, like putting them in Base URLs would. It simply allows walking them - if a reference to them is encountered via walking the existing Base URLs etc. Thus if no links to Extra Domains are encountered, none will be walked.