[SR-Users] Kamailio + rtpproxy talking to multiple carrier gateways

[Alex Balashov]

On 09/05/2011 08:07 PM, Sarat C. Vemuri wrote:

> How do I remove the "public IP" entry from the route set before
> forwarding the reply to Internal UAC?

You don't -- at least, not in a protocol-compliant way.  You can, of 
course, do remove_hf("Route"); if you want to, but with effects that are 
ultimately rather undesirable, I think.

One strategy I've used for dealing with this in the past, nasty as it 
is, is to:

1. Create a loopback interface on the proxy with the address of its 
public IP.

2. Set static routes for that public IP from all the "internal" servers 
on the private LAN pointing to the proxy.

3. Bind Kamailio to that loopback interface only, enable IP forwarding, 
and define the "real" interface addresses as alias=es.

4. DNAT all incoming traffic on the "real" interfaces, in the PREROUTING 
table, to have the destination IP of the public IP of the proxy (the 
loopback interface).

Works for rtpproxy too, but of course, relies on ugly NAT and limits you 
to what the conntrack facility can reasonably handle.


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Alex Balashov - Principal
Evariste Systems LLC
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