[SR-Users] question about NAT being behind of a Load Balancer

Albert Petit albertpetit at gmail.com
Fri Feb 3 10:26:15 CET 2012


Hi , Sorry for previous email. Hit send too soon .

Good morning,
On my system i've a structure similar to:

 SIP Clients                    SIP Platform
[-------------------]        [---------------------------------]
                                              S1 @IP2

                                              S2 @IP3
  SIP UACs              SIP LB                    ...
 [NATted and            @IP1
 non Nattted]
                                               SN  @IPN


SIP LB is based on Kamailio dispatcher and is responsible of distributing
the load between different Servers SIP UAS.

S1, S2,... SN Servers have a Kamailio Server too which will forward
received balanced traffic to appropiate service (Presence , registrar,...)


Considering SIP LB and all SIP UAS have Public IP, how NAT from the UACs
could be handled on this scenario?

Initially I thought NAT should be handled on SIP LB however I would like
the most simple possible load balancer with no need to read user locations
. Responsible of location users should be S1,S2,..:SN

Then, would  it be possible to handle NAT of the SIP UACs *from the SIP UAS
 *with NAT Helper module? What i'm afraid is:      If all traffic to
S1,S2,..SN comes from SIP LB then nat_helper could think all clients are
NATTed because top most via will be SIP LB.


What I need, I think, is that NAT Helper decides if there is NAT looking
the Via Header added originally by UAC , and not the top most via (which
would be SIP LB). Is that possible? If possible how should i configure Nat
helper for that?


BR
Albert
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