Forwarding Broadcast over VPN

[mattKnight]

Hi

I need to pick soem Cisco gurus' brains...

I have 3 sites connected together by VPNs using ciscos ( 2 x 877 and a 18xx if the model numbers are crucial I can find out..)

I have a phone system that on 1 site that communicates phoen status information (busy, idle, DND etc) to software clients by UDP broadcast on port 50799. This works fine on a single subnet, but when used with remote subnets only 10 of these software clients work (remote clients use unicast rather than broadcast)

I believe that "crafty" use of

ip forward-protocol udp 50799

will allow/cause UDP packets to be broadcast to subnets, if

IP helper address

is enabled on the correct interface(s)

Question 1. - Is this correct or incorrect, or a bit of both?

having looked at he IP helper address syntax, I believe I need to specify the destination address, which whilst possible would be a PITA.

Question 2. - Have I understood the syntax correctly?

Question 3. - Would

IP forward-protcol spanning-tree

be a solution?

Thanks for the thoughts...

Take Care

Matt
I have always wished that my computer would be as easy to use as my telephone.
My wish has come true. I no longer know how to use my telephone.

 

[burtsbees]

The ip forward-protocol forwards specific ports for broadcast, whichever you specify. The ip-helper address (note the dash between "helper" and "address") forwards a specific handful of tcp/udp ports to an IP address that you specify...the ports are
TFTP, Domain Name System (DNS), Time, NetBIOS, ND, BOOTP or DHCP

More info here...

http://www.cisco.com/en/US/docs/ios/12_3t/ip_addr/command/reference/ip1_i1gt.html#wp1169356

Sounds like we needs a better design description (topology)---maybe you need to forward the broadcasts in more than just the one device? Forwarding spanning-tree...huh? Never heard of that---that would just forward stp past its own broadcast domain, blocking non-redundant switchports possibly...I don't think I would do that, and it certainly would not solve your problem, unless someone could shed some different light on the subject...

Burt