Remote Extension from specific location not working IP address shows private IP instead of Public IP

I have a real weird problem, I am new to freepbx and asterisk. Thanks for all the help topics I have been able to successfully install and use it. I have few extensions in the US and a few in India. Everything works fine. I have the server on a static IP behind a firewall. All settings in sip.conf and other conf files are setup. I am able to register remote extensions from several locations w/o any issues. I am only running into access from 1 particular location.

It registers and then immediately it is gone.
[2013-09-29 17:04:00] VERBOSE[5122] chan_sip.c: – Registered SIP ‘298’ at 192.168.1.100:5062
[2013-09-29 17:04:04] NOTICE[5122] chan_sip.c: Peer ‘298’ is now UNREACHABLE! Last qualify: 0 .
Same thing happens with zoiper softphone on a mobile device and grandstream 1400.
However, if the same mobile device uses 3g data network it works fine.

Weird thing I noticed is that it lists the private IP address of the device when I checked sip show peer on CLI. for other remote extensions it showed the public IP.
298 isn’t working… 201 is working fine from another location in India.

  • Name : 298
    Description :
    Secret :
    MD5Secret :
    Remote Secret:
    Context : from-internal
    Record On feature : automon
    Record Off feature : automon
    Subscr.Cont. :
    Language :
    Tonezone :
    AMA flags : Unknown
    Transfer mode: open
    CallingPres : Presentation Allowed, Not Screened
    Callgroup :
    Pickupgroup :
    Named Callgr :
    Nam. Pickupgr:
    MOH Suggest :
    Mailbox : [email protected]
    VM Extension : *97
    LastMsgsSent : 0/0
    Call limit : 2147483647
    Max forwards : 0
    Dynamic : Yes
    Callerid : “Saurabh Home” <298>
    MaxCallBR : 384 kbps
    Expire : 2816
    Insecure : no
    Force rport : No
    Symmetric RTP: No
    ACL : Yes
    DirectMedACL : No
    T.38 support : No
    T.38 EC mode : Unknown
    T.38 MaxDtgrm: -1
    DirectMedia : No
    PromiscRedir : No
    User=Phone : No
    Video Support: No
    Text Support : No
    Ign SDP ver : No
    Trust RPID : Yes
    Send RPID : No
    Subscriptions: Yes
    Overlap dial : Yes
    DTMFmode : rfc2833
    Timer T1 : 500
    Timer B : 32000
    ToHost :
    Addr->IP : 192.168.1.100:5062
    Defaddr->IP : (null)
    Prim.Transp. : UDP
    Allowed.Trsp : UDP
    Def. Username: 298
    SIP Options : (none)
    Codecs : (gsm|ulaw|alaw)
    Codec Order : (ulaw:20,alaw:20,gsm:20)
    Auto-Framing : No
    Status : UNREACHABLE
    Useragent : Grandstream GXP1400 1.0.5.23
    Reg. Contact : sip:[email protected]:5062
    Qualify Freq : 60000 ms
    Keepalive : 0 ms
    Sess-Timers : Refuse
    Sess-Refresh : uas
    Sess-Expires : 180 secs
    Min-Sess : 90 secs
    RTP Engine : asterisk
    Parkinglot :
    Use Reason : No
    Encryption : No

201 works fine… noice the IP address

  • Name : 201
    Description :
    Secret :
    MD5Secret :
    Remote Secret:
    Context : from-internal
    Record On feature : automon
    Record Off feature : automon
    Subscr.Cont. :
    Language :
    Tonezone :
    AMA flags : Unknown
    Transfer mode: open
    CallingPres : Presentation Allowed, Not Screened
    Callgroup :
    Pickupgroup :
    Named Callgr :
    Nam. Pickupgr:
    MOH Suggest :
    Mailbox : [email protected]
    VM Extension : *97
    LastMsgsSent : 10/0
    Call limit : 2147483647
    Max forwards : 0
    Dynamic : Yes
    Callerid : “Saurabh Chandra” <201>
    MaxCallBR : 384 kbps
    Expire : 2827
    Insecure : no
    Force rport : No
    Symmetric RTP: No
    ACL : Yes
    DirectMedACL : No
    T.38 support : No
    T.38 EC mode : Unknown
    T.38 MaxDtgrm: -1
    DirectMedia : No
    PromiscRedir : No
    User=Phone : No
    Video Support: No
    Text Support : No
    Ign SDP ver : No
    Trust RPID : Yes
    Send RPID : No
    Subscriptions: Yes
    Overlap dial : Yes
    DTMFmode : rfc2833
    Timer T1 : 500
    Timer B : 32000
    ToHost :
    Addr->IP : 122.172.xxx.xxx:5060
    Defaddr->IP : (null)
    Prim.Transp. : UDP
    Allowed.Trsp : UDP
    Def. Username: 201
    SIP Options : (none)
    Codecs : (gsm|ulaw|alaw)
    Codec Order : (ulaw:20,alaw:20,gsm:20)
    Auto-Framing : No
    Status : OK (342 ms)
    Useragent : Grandstream GXP2100 1.0.5.26
    Reg. Contact : sip:[email protected]:5060
    Qualify Freq : 60000 ms
    Keepalive : 0 ms
    Sess-Timers : Refuse
    Sess-Refresh : uas
    Sess-Expires : 180 secs
    Min-Sess : 90 secs
    RTP Engine : asterisk
    Parkinglot :
    Use Reason : No
    Encryption : No

I think this may be a router or ISP related issue on the remote side… I tried changing the router and same issue…
Can someone please guide me to a possible resolution. and where can I look…

Thank you in advance.