[Asterisk-Users] Two server

[AsteriskList]

Hello
Use two Asterisk servers.
I registered Server2 in Server1. When I bind for an extension in the
Server1, the hard call some as and is interrupted.
My configuration:
iax.conf / Server 1
[20001]
type=friend
accountcode=20001
host=dynamic
secret=secret
context=sip
disallow=all
allow=gsm
auth=plaintext
//////////////////////////////////////////////////////
iax.conf / Server 2
register => 20001:secret at ipserver1

[20001]
type=user
context=fromiax
auth=plaintext

Extension / Server2
exten => _33.,1,SetCallerId,${CALLERIDNUM}
exten => _33.,2,Dial(IAX2/20001:secret at ipserver1/${EXTEN:2})
exten => _33.,3,Congestion

Error
 -- Executing Dial("IAX2[40002 at 40002]/17",
"IAX2/20001:secret at ipserver1/123456") in new stack
    -- Called 20001:secret at ipserver1/123456
    -- Call accepted by 24.232.89.22 (format GSM)
    -- Format for call is GSM
    -- Operating with different codecs, can't native bridge...
    -- Hungup
  == Spawn extension (sip, 33123456, 2) exited non-zero on
'IAX2[40002 at 40002]/17'
    -- Hungup 'IAX2[40002 at 40002]/17'


Necessary of aid. It forgives my English.
Thanks
Tiago