This is from the www.echolink.org site
Linksys
Using a Web browser, bring up your router's configuration page. By default, the URL is 192.168.1.1, the user name is blank, and the password is "admin".
Click the Advanced tab.
Click the Forwarding tab.
In the first pair of Service Port Range boxes along the top, enter 5198 and 5199.
On the same line, under Protocol, choose UDP.
On the same line, enter the IP address of the computer running EchoLink.
Click Apply to save changes.
Hope this helps
Randy VE3WRN