Enable VLAN on WAN interface for Cisco SRP527W

Several years ago, I advised a friend of mine to buy the Cisco SRP527W, a SME DSL router with built-in voice capabilities. At the time, it was one of the supported devices for his broadband provider’s VOIP services.

This is a companion discussion topic for the original entry at https://www.funkypenguin.co.nz/howto/enable-vlan-on-wan-interface-for-cisco-srp527w/