From: Rich Collins (nilsi2002@gmail.com)
Date: Wed Jun 04 2008 - 16:55:17 ART
Hi,
You should really think of the command as "ip directed broadcast
forwarding". You don't need it on RouterA. The e0/0 interface does
respond to a broadcast - like a ping to its broadcast address.
You will need it however on the egress point of RouterB (eth0/0). You'll
notice that in the Cisco documentation.
-Rich
On Tue, Jun 3, 2008 at 11:05 PM, David Lonnie <david.lonnie@gmail.com>
wrote:
> Hi,all:
>
> I'm reading a book named "CCIE developing ip multicast networks" that Cisco
> pressed.
> I'm confusing here.
> You need to convert broadcast to multicast on Router A, and then convert
> multicast to broadcast on Router B.
>
> -------- (e0/0)A(s0/0)--------------(s0/0)B(e0/0)--------
>
> This is the context I quote.
>
>
> Example 16-23: Router A Configuration
> Interface Ethernet0
> ip address 10.1.1.10 255.255.255.0
> ip directed-broadcasts
> ip multicast helper-map broadcast 224.1.1.1 100 ttl 15
> access-list 100 permit any any udp 2000
> access-list 100 deny any any udp
> ip forward-protocol udp 2000
>
> In addition to the ip multicast helper-map command, the ip
> directed-broadcasts command was added
> to the Ethernet0. This command is necessary to enable the router to process
> the incoming broadcast
> packets on Ethernet0. If this command were not added, the router would
> simply ignore all incoming
> broadcast packets on this interface and they would not get translated to
> multicast. Even with this
> command added, the router will process only those broadcast packets with
> certain standard UDP port
> numbers (TFTP, BOOTP, DNS, NetBIOS Name Server, NetBIOS Datagram Server,
> and
> TACACS) by
> default. Therefore, it is also necessary to add the ip forward-protocol udp
> 2000 command to instruct
> the router to also process the incoming broadcast packets with a UDP
> destination port of 2000.
>
> But when i read Doc CD.
>
> http://www.cisco.com/en/US/docs/ios/ipmulti/configuration/guide/imc_inter_mc_helper_ps6350_TSD_Products_Configuration_Guide_Chapter.html#wp1056657
> there is no "ip directed-broadcasts" command.
>
> My question is that what does this command really mean.Can anybody help me
> to make a choice when in the lab?
>
>
> Thanks in advance.
>
> David
>
>
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