3rd attempt to post it to the list, please ignore if it is duplicate

I have the following problem

When trying to setup asterisk 13.1 with PJSIP to connect to my IPV6 capable SIP provider the registration fails.

[code][Dec 22 19:24:24] DEBUG[25247] pjsip: tsx0x110736c .Transaction created for Request msg REGISTER/cseq=36181 (tdta0x721d90)
[Dec 22 19:24:24] DEBUG[25247] pjsip: tsx0x110736c Sending Request msg REGISTER/cseq=36181 (tdta0x721d90) in state Null
[Dec 22 19:24:24] DEBUG[25247] pjsip: sip_resolve.c .Starting async DNS A query: target=sip1.easybell.de, transport=Unspecified, port=5060
[Dec 22 19:24:24] DEBUG[25247] pjsip: resolver.c .Transmitting 34
bytes to NS 0 (192.168.178.1:53): DNS A query for sip1.easybell.de: Success
[Dec 22 19:24:24] DEBUG[25247] pjsip: tsx0x110736c .State changed from Null to Calling, event=TX_MSG
[Dec 22 19:24:24] DEBUG[25252] pjsip: resolver.c Received 50 bytes DNS response from 192.168.178.1:53
[Dec 22 19:24:24] DEBUG[25252] pjsip: resolver.c Nameserver
192.168.178.1:53 state changed Active –> Active
[Dec 22 19:24:24] WARNING[25252] pjsip: tsx0x110736c Failed to send Request msg REGISTER/cseq=36181 (tdta0x721d90)! err=171064 (Unsuitable transport selected (PJSIP_ETPNOTSUITABLE))
[Dec 22 19:24:24] DEBUG[25252] pjsip: tsx0x110736c State changed from Calling to Terminated, event=TRANSPORT_ERROR
[Dec 22 19:24:24] DEBUG[25252] pjsip: tsx0x110736c Timeout timer event
[Dec 22 19:24:24] WARNING[25247] res_pjsip_outbound_registration.c: No response received from ‘sip:sip1.easybell.de:5060’ on registration attempt to ‘sip:004970718604945@sip1.easybell.de:5060′, retrying in ’60’
[Dec 22 19:24:24] DEBUG[25252] pjsip: tsx0x110736c .State changed from Terminated to Destroyed, event=TIMER
[/code]

For my naive eyes it looks as if there is no ipv6 name resolution (a DNS
AAAA query) performed.

Here are the (relevant) entries in the configuration files:

pjsip.conf
[code][udp-ipv6]
type=transport protocol=udp bind=[2a02:8070:86c0:2ca0:ba27:ebff:feda:bbb6]:5060

…

[endpoint-ipv6](!)
type=endpoint context=ExternalSets transport=udp-ipv6
rtp_ipv6=yes disallow=all
;allow=g722
allow=alaw allow=gsm allow=g726
allow=ulaw

[registration-ipv6](!)
type=registration transport=udp-ipv6
;auth_rejection_permanent=no retry_interval=60

[easybell](registration-ipv6)
outbound_auth=easybell server_uri=sip:sip1.easybell.de:5060
client_uri=sip:@sip1.easybell.de:5060

[easybell](endpoint-ipv6)
;context=ExternalSets outbound_auth=easybell aors=easybell[/code]

The own IPV6 address is recognized:

[code][Dec 22 19:24:14] DEBUG[25222] pjsip: udpv60x998200 SIP UDP IPv6
transport started, published address is
[2a02:8070:86c0:2ca0:ba27:ebff:feda:bbb6]:5060

…

[Dec 22 19:24:20] VERBOSE[25222] res_pjsip_multihomed.c: Local IPv4 address determined to be: 192.168.178.99
[Dec 22 19:24:20] VERBOSE[25222] res_pjsip_multihomed.c: Local IPv6 address determined to be: [2a02:8070:86c0:2ca0:ba27:ebff:feda:bbb6][/code]

The IP address of the partner is recognized:
[code][Dec 22 19:24:20] VERBOSE[25222] config.c: Parsing
‘/etc/asterisk/pjsip.conf’: Found
[Dec 22 19:24:20] DEBUG[25222] netsock2.c: Splitting ‘sip1.easybell.de’
into…
[Dec 22 19:24:20] DEBUG[25222] netsock2.c: …host ‘sip1.easybell.de’ and port ”.
[Dec 22 19:24:20] DEBUG[25222] netsock2.c: Splitting ‘2001:4090:4008::124’
into…
[Dec 22 19:24:20] DEBUG[25222] netsock2.c: …host ‘2001:4090:4008::124’
and port ”.
[Dec 22 19:24:20] DEBUG[25222] acl.c:
[2001:4090:4008::124]:0/[ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff]:0 sense 0
appended to ACL[/code]

The problem is when Asterisk tries to [b]register[/b] with the other host.

Anyone have an idea what is wrong or missing, I am appreciating any hint.

Thank you in advance!

R