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Webcast-Catalyst9k

Allow Broadcasts

I want to allow broadcast packets to pass through router.

I want to pass only UDP packets on port 137 through every network port on router, no other port and no other protocol doing broadcasts.

How to do that?

3 REPLIES
Bronze

Re: Allow Broadcasts

Hi

You could do it with the following two commands

ip helper-address x.x.x.x

With this command you will change certain broadcasts into a unicast and forward it to the speciefied address.

With the command no ip forward-protocol udp "xy" you can disable the one's you don't need.

Here are the ud ports which will be forwarded with the helper command:

TFTP (69)

DNS (53)

Time (37)

NetBios name Server (137)

NetBios datagram Service (138)

BOOTP server (67)

BOOTP client (68)

Tacacs (49)

Hope that helps

Roger

Re: Allow Broadcasts

I want to do it for Netbios name resolution ( UDP, port 137 ) , what will be the exact command for that?

What does this command means? I need to allow all broadcasts and then deny the unwanted, like access lists?

Bronze

Re: Allow Broadcasts

So do

ip helper-address "ip adr. to which you like to forward"

no ip forward-protocol 69

no ip forward-protocol 53

no ip forward-protocol 37

no ip forward-protocol 138

no ip forward-protocol 67

no ip forward-protocol 68

no ip forward-protocol 49

That's all.

Roger

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