Broadcasts not being forwarded between subnets

[grandezd]

I'm having problems trying to print from Workstations on subnet 192.168.0.0/24 to a printer on a different subnet 208.94.207.160/27. The printer is attached to a Linksys wireless print server (208.94.207.180). Both subnets are interconnected via a 3640 router. Please see below:

192.168.0.0/24 FA0/1 FA0/0 208.94.207.180

PC-------------3640ROUTER---AP-))((-PrintSvr--Printer

Note: The Printer and Wireless Print Server work fine when used by workstations on the same subnet (208.94.207.160/24)

The print server Driver installed on workstations sends broadcasts to locate the Print Server. This can be seen from the following transaction information captured with a sniffer:

PACKET SENT FROM WORKSTATION BY PRINT SERVER DRIVER:

L2: DESTINATION: FFFF.FFFF.FFFF

SOURCE: <WORKSTATION's MAC>

L3(IP): DESTINATION: 255.255.255.255

SOURCE: 192.168.0.2

L4(UDP):DESTINATION 34444 OR 34333

SOURCE: <DYNAMICALLY ASSIGNED>

A Workstation on subnet 192 does not receive a reply from the Print Server, whereas a Workstation on 208 subnet does.

This is totally understandable since a router by default separates broadcast domains.

So, I tried adding "ip helper-address" and "ip broadcast-address" commands, but same difference: broadcasts are not being forwarded.

I have attached a simplified version of the router config. Could someone please shed some light on this? Your support will be greatly appreciated.

Thanks in advance,

David

[dbellazetin · Accepted solution]

David,

ip helper-address only forwards a few common broadcast UDP ports by default. You need to add to that using the "ip forward-protocol" command in global configuration. Just specify the UDP port number that is in your sniffer capture and that should probably solve this problem for you.

Daniel

[grandezd]

Daniel,

Many thanks for the advice. It worked!

David

P.S: Is there a command that I can use to see what ports are being forwarded by default?