Routing broadcast traffic to multicast by port number

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Jul 27th, 2007
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I'm a bit of a noobie, so you will have to bear with me (well, you don't but I'd appreciate it). I have three 2811 routers connecting three remote sites to the main network at my location. Currently, the remote sites are broadcasting data to UDP ports 3000-3200 where each data source gets its own port. The routers are set up to take the broadcast traffic and turn it into multicast traffic using the "ip multicast helper-map" command. Other than that, there is nothing exotic about the configuration.

What I would like to do is map each UDP port to its own multicast address in the 239.192.1.XXX range. It looks like I might be able to do this with static NAT, but it seems like a kludge to me. One other kink is that each source IP can transmit up to 3 different data streams AND data streams may be associated with multiple IP addresses.

Has anyone else run into a situation like this or does anyone have any idea how to do what I'm describing. Thanks in advance.


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ougryphon Mon, 07/30/2007 - 09:39
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After reading EdisonOrtiz's post about PBR, I thought I would give PBR a try. Here's what I tried:

ip access-list extended PORT3001

permit udp eq 3001 any

route-map RM-PORTS permit 10

match ip address PORT3001

set ip default next-hop

The last line gave me an error "Martian next hop not allowed". Reading more, it looks like it either doesn't like multicast addresses or it doesn't like destination addresses for which there is not a corresponding exit interface with the same subnet. Just for grins, I tried setting the address of a loopback interface to a multicast address and, of course, got an illegal address error. I don't know if this would have helped any way, but I'm to the point of randomly trying things to get this working. Does anyone have any ideas? Help would be very much appreciated.

ougryphon Tue, 07/31/2007 - 07:22
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Thank you for your reply. The configuration in the example is what I'm already using to convert broadcast to a single multicast address. Unless I'm missing something, the "ip multicast helper-map" command only lets you set one multicast address. What I need is a separate multicast address for each port number.


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