[cisco-bba] cisco-bba Digest, Vol 56, Issue 4

Andy Saykao andy.saykao at staff.netspace.net.au
Mon Feb 11 02:38:14 EST 2008

I love to use dispatch mode but the silly Cisco Call Manager 5.1 servers
only support 1 IP address and as such we can't bound any further IP's to
the NIC or loopback.

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Today's Topics:

   1. Re: Does SLB support SIP? (Robert Blayzor)


Message: 1
Date: Thu, 07 Feb 2008 19:48:06 -0500
From: Robert Blayzor <rblayzor.bulk at inoc.net>
Subject: Re: [cisco-bba] Does SLB support SIP?
To: Andy Saykao <andy.saykao at staff.netspace.net.au>
Cc: cisco-bba at puck.nether.net
Message-ID: <47ABA6C6.20704 at inoc.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Andy Saykao wrote:
> I'm finding that the SIP headers do not have any of CCM IP's in them
> ( or so obviously the packet gets discarded 
> when it hits the CCM. Instead the SIP header has the FROM: address as 
> the SIP gateway IP (203.10.x.x) and the TO: address as the virtual 
> server IP
> (210.15.x.x) (which we've set the SIP gateway to forward to) - is 
> there anyway to have TO address changed to so the SIP 
> call hits the SLB and then is load balanced to one of the CCM's???

Your problem is not SLB, it's NAT.  There isn't any mechanism in IOS (at
least that I"m aware of) or rewrite SIP messages to contain the right

Perhaps the best option is to ditch SLB + NAT and go to dispatch  mode,
where the real servers are aware of the virutal addresses via directly
connected (ie: loopback address).  Of course you'll have a problem with
UDP based SIP (my guess).

Robert Blayzor
rblayzor at inoc.net

Debugger: A tool that substitutes afterthought for forethought.


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