Unable to support trunking

Hy,i have next error when i try call over iax trunk on all machines (PC-1 and PC-2)!

[Apr 5 12:22:20] NOTICE[2611]: chan_iax2.c:9905 set_config: Ignoring bindport on reload
== Parsing ‘/etc/asterisk/users.conf’: Found
> doing dnsmgr_lookup for ‘216.207.245.47’
> doing dnsmgr_lookup for ‘Ip address 2’
[Apr 5 12:22:20] WARNING[2611]: chan_iax2.c:9366 build_peer: Unable to support trunking on peer ‘name_of_iax’ without zaptel timing
[Apr 5 12:22:20] WARNING[2611]: chan_iax2.c:9624 build_user: Unable to support trunking on user ‘name_of_iax’ without zaptel timing
> doing dnsmgr_lookup for ‘Ip address 2’
== Loaded firmware ‘iaxy.bin’

Please, can someone tell me what is the problem?

Best regards.

Iax Configuration:

PC-1

['name_of_iax]
nat=yes
type=peer
username=gredauser
secret=gredauser
auth=plaintext
host=IP_address_1
context=incoming_iax_greda
qualify=yes
trunk=yes
disallow=all
allow=gsm
allow=alaw

[name_of_iax]
nat=yes
type=user
username=gredapeer
secret=gredapeer
auth=plaintext
host=IP_address_1
context=incoming_iax_greda
qualify=yes
trunk=yes
disallow=all
allow=gsm
allow=alaw

PC-2

[name_of_iax2]
nat=yes
type=peer
username=gredapeer
secret=gredapeer
auth=plaintext
host=IP_address_2
context=incoming_iax_greda
qualify=yes
trunk=yes
disallow=all
allow=gsm
allow=alaw
port=4569
permit=0.0.0.0/0.0.0.0

[name_of_iax2]
nat=yes
type=user
username=gredauser
secret=gredauser
auth=plaintext
host=IP_address_1
context=incoming_iax_greda
qualify=yes
trunk=yes
disallow=all
allow=gsm
allow=alaw
port=4569
permit=0.0.0.0/0.0.0.0