When researching this matter (I wanted to enable neighbor discover on new L2TP tunnels internal to our network) I found that this command line can disable it by default: /ip neighbor discovery settings set default=no default-for-dynamic=no The "default" is for manually created interfaces like IPIP tunnels, the "default-for-dynamic" is for dynamic interfaces like the server-side of L2TP tunnels. With this command issued once, the discovery should be off on new tunnels on versions < 6.41 However, this command no longer exists in 6.41 ! Now, setting of discovery is done using an interface list with the members of the list participating in discovery (or the non-members, there is an inversion operator) So look in the "ip neighbor" discovery settings to see how the interfaces are now set, there can be an interface list "discover" (the new default) or there can be something like "!dynamic" which results in discovery on all non-dynamic interfaces (the old default). When it says "!dynamic" it is better to change that to "discover" and put only your local interfaces in that list. Rob