The way you  have #2 written is bothering me, if you only have one interface 
period you should never need to bind, but if you only have one egress interface 
and need certain traffic to be on IP A and some on IP B (via loopbacks) then 
you would need to bind and that is my scenario.


I have a complicated (to me!) routing situation and I need my PSTN traffic to 
the ITSP to be on an IP that only they know about and my internal traffic to be 
the same. This was the best way I could think of to make that happen.







Matthew Loraditch
Sr. Network Engineer
p: 443.541.1518
w: www.heliontechnologies.com | e: mloradi...@heliontechnologies.com
From: Anthony Holloway <avholloway+cisco-v...@gmail.com>
Sent: Friday, September 11, 2020 5:46 PM
To: Matthew Loraditch <mloradi...@heliontechnologies.com>
Cc: cisco-voip@puck.nether.net
Subject: Re: [cisco-voip] SIP Binding: Different Binds for Carrier vs Internal

[EXTERNAL]

First up, you don't need to bind your interfaces.  You should bind your 
interfaces in two scenarios though:

1. You're trying to source your IP from a loopback address
2. You only have one interface

Otherwise, let the router do it's routing and it will pick the correct 
interface to "bind" SIP too, by the nature of which interface the packet leaves 
the router from.

Now, you can bind, if you want to, but it doesn't do anything extra, to the 
best of my knowledge.

When you say, "[n]ever see the other’s IP," you should know that this happens 
by default.  That's what a B2BUA does.  It terminates a dialog with one peer, 
and then turns around and originates a new dialog with a different peer.

And yes, flow through is default, but that does not affect signaling, which it 
kind of sounds like is the topic at hand.  Otherwise, flow around means your 
carrier knows how to hit your inside IP Phone addresses directly, and that's 
not likely the case.

So literally, you do not have to do anything extra or special to get what you 
want.  You simply configure the router as a device with two interfaces on two 
different networks, and teach it how to route (e.g., static routing or 
something, I don't know I'm not a CCIE Routing and Switching).

On Fri, Sep 11, 2020 at 2:25 PM Matthew Loraditch 
<mloradi...@heliontechnologies.com<mailto:mloradi...@heliontechnologies.com>> 
wrote:
I need to bind call legs to my carrier to one IP and all legs to CUCM on 
another IP on the same router and neither side ever see the other’s IP nor need 
to route to it

I’ve done something, at least similar, many years in the past but no longer 
have access to the environment to verify the behavior and am trying to refresh 
myself on the setting.

In that setup we bound the dial peers to the relevant interfaces and enabled 
allow-connections sip to sip and address-hiding in my voice service voip config.

>From what I further understand media flow-through is the default behavior so 
>as long as I do the binding, I will get what I want to happen happening.

Am I generally correct in all of my current thoughts? Anything I’m not thinking 
of?






Matthew Loraditch​
Sr. Network Engineer
p: 443.541.1518<tel:443.541.1518>
w: www.heliontechnologies.com<http://www.heliontechnologies.com/>
 |
e: mloradi...@heliontechnologies.com<mailto:mloradi...@heliontechnologies.com>
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