[Freeswitch-users] Need to enable NDLB_force_port to work properly with Windows PC Internet Gateway

[Randy Andrade]

It sounds like the Windows Internet Gateway is performing a standard PAT
(port address translation) version of NAT, but since it is not SIP aware, it
is not smart enough to realize that the SIP header contains directions to
reply on a specific port (5060) it just figures "if I pass this data out
port 62000, I expect it back on port 62000" it doesn't know anything about
what the data contains..

Most routers have (at least a limited) an awareness of SIP traffic, so they
"read" the SIP messages and manipulate port information when it re-sends the
packet. That's to say when it passes the data out port 62000 on the public /
WAN interface, it's changed the SIP header to tell FS to reply back on port
62000.. when it gets the reply, it then changes the SIP header again and
passes the message back to the ATA on port 5060 of it's private / LAN
interface.

On Wed, Apr 6, 2011 at 9:05 AM, Vitalii Colosov <vetali100 at gmail.com> wrote:

> Hi Randy,
> Thanks for the advice.
>
> In general yes, there are always some options to be considered.
>
> But mostly I am curious now - is Windows Internet gateway really not
> following the standards, or it is just a matter of proper configuration?
>
> Vitalie
>
>
> 2011/4/6 Randy Andrade <randy.andrade at gmail.com>
>
>> Is there no option of putting an inexpensive switch or router in front of
>> the Windows PC to perform Internet Gateway function? It would probably be
>> the preferred methodology.
>>
>> On Wed, Apr 6, 2011 at 8:49 AM, Vitalii Colosov <vetali100 at gmail.com>wrote:
>>
>>> Hi list,
>>>
>>> I am testing the following configuration:
>>>
>>> Sip ATA adapter (Linksys PAP2) -> Windows PC (Internet Gateway) -> ...
>>> Internet ... -> FreeSWITCH
>>>
>>> Sip adapter sends REGISTER to the FS, from port 5060, however Windows
>>> Gateway transfers this packet to FS from a different port (for example
>>> 62000).
>>> FS replies to the port 5060 (it looks like it takes it from the SIP text
>>> information).
>>> So Windows Gateway receives the answer to the port 5060, but since it
>>> expects  it to be received in 62000, it looks like it drops the packets.
>>>
>>> The only way to fix this, is to set NDLB_force_port= true in the internal
>>> profile configuration file.
>>> In this case, FreeSWITCH replies exactly to the port 62000, and windows
>>> forwards it to the Sip adapter on port 5060.
>>>
>>>
>>> Do you know whether it is possible to configure Windows to route
>>> properly?
>>> Or maybe there is a way to configure the Sip adapter? (Like it will say
>>> to windows PC - hey, don't change the port, use the same as I am using...
>>> :)) Or it is a fantastic wish)
>>>
>>> Otherwise I will have to create 2 internal sip profiles, one
>>> with NDLB_force_port = true (for those who uses Windows PC as the gateway),
>>> and another with NDLB_force_port = false (for those who use normal routers).
>>> And I need 2 default dialplans, etc... so it complicates the solution.
>>>
>>>
>>> Thank you,
>>> Vitalie
>>>
>>>
>>>
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>>
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