This works for us. We create the main DIDww trunk in the GUI and then setup inbound trunks
for each additional IP in sip_custom.conf like below all pointing to the same context "from-trunk-sip-DIDww".
This will also open up the ports in the integrated firewall.
;DIDww
[46.19.209.11]
host = 46.19.209.11
type=peer
disallow=all
allow=alaw
context=from-trunk-sip-DIDww