Мне даже стыдно.
Действительно кнопка находится в
Tools - System Settings.
Но вот вам отрывок со свтроеной спраки:
"
Miscellaneous Item
These are additional tools and features of the DSL-500T.
Ping Test - This useful diagnostic utility can be used to check if a computer is on the internet. It sends ping packets and listens for replies from the specific host.
IGMP Proxy - Here is the global setting for IGMP Proxy. If it is enabled, then the enabled IGMP Porxy on WAN PVCs will be working. Otherwise, no WAN PVC can have IGMP Proxy working on it.
Save and Reboot - Settings need to be saved to Flash and the system needs to be rebooted for changes to take effect."
Спасибо за внимание.