Incoming Calls

Peer Section

Accept authenticated calls and route them to a context.

[aaisp-incoming-username]
type=peer
context=aaisp-incoming-context
secret=aaisp-incoming-password
transport=udp
disallow=all
allow=alaw
trustrpid=yes

Authentication

Voiceless must authenticated so that calls are recognised as the above peer section.
There are two options: either detect Voiceless and ask it to authenticate, or request that every rejected INVITE from all sources authenticates.
In both cases you need to use the match_auth_username=yes setting otherwise Asterisk will not recognise Voiceless' username.

Authenticate Everyone

This is the more secure option as it stops your usernames from being enumerated by brute force.
You can't allow a default guest context (unauthenticated calls) or calls from Voiceless will use it.

[general]
allowguest=no
alwaysauthreject=yes
match_auth_username=yes

Authenticate Voiceless

This is the more complex option as you need to list every Voiceless name.
It is the only option if you need to allow the default guest context (unauthenticated calls).

[general]
; allowguest=yes
; alwaysauthreject=no
match_auth_username=yes

[aaisp-voiceless]
type=peer
md5secret=intentionally_invalid_md5_string

[aaisp-voiceless-a4](aaisp-voiceless)
host=a4.voiceless.aa.net.uk
defaultip=81.187.30.111

[aaisp-voiceless-b4](aaisp-voiceless)
host=b4.voiceless.aa.net.uk
defaultip=81.187.30.113

[aaisp-voiceless-c4](aaisp-voiceless)
host=c4.voiceless.aa.net.uk
defaultip=81.187.30.112

[aaisp-voiceless-d4](aaisp-voiceless)
host=d4.voiceless.aa.net.uk
defaultip=81.187.30.114

Outgoing Calls

Either use a separate type=user section or combine incoming and outgoing in one type=friend section

Separate Section

[aaisp-outgoing-account]
type=user
host=voiceless.aa.net.uk
defaultip=81.187.30.111
username=aaisp-phone-number
remotesecret=aaisp-outgoing-password
transport=udp
disallow=all
allow=alaw

Combined Section

[aaisp-incoming-username]
type=friend
transport=udp
disallow=all
allow=alaw
; incoming
context=aaisp-incoming-context
secret=aaisp-incoming-password
trustrpid=yes
; outgoing
host=voiceless.aa.net.uk
defaultip=81.187.30.111
username=aaisp-phone-number
remotesecret=aaisp-outgoing-password