From: Deepesh Chouhan (deepesh@cisco.com)
Date: Fri May 16 2003 - 16:05:19 GMT-3
There are so many advantages of controlling broadcast. I'm mentioning just
one of them
take this scenario
rtr1---1.x.x.x/8---(e1/0)rtr2(e1/1)---2.x.x.x/8---some_server
rtr1 is sending a all 1's broadcast .. i.e.
l3_src = 1.1.1.1
l3_dest = 255.255.255.255
1.
rtr2 will by default drop the broadcast packets. Let's assume you issue
global command which allows it to process it. This command is ip
forward-protocol.
rtr2 now process the broadcast and sends it on all IP interfaces except
where it came in.
But some_server does not understand l3_dest=255.255.255.255. In that case,
for e1/1 on rtr2 we issue ip directed-broadcast.
it converts l3_dest=255.255.255.255 to l3_dest=2.255.255.255 (broadcast
address for 2.x.x.x/8) so that some_server can understand it
2. if you issue ip directed broadcast, it automatically configures global
'ip forward-protocol udp' for you. Use this command only if rtr1 is sending
something else besides UDP
3. One more thing. Let's say some_server can't understand
l3_dest=2.255.255.255.
In that case you can configure on e1/0 of rtr2 - ip helper-address 2.1.1.2
(ip addr of some_server). In this case rtr2 changes l3_dest=255.255.255.255
to l3_dest=2.1.1.2 (unicast)
4. same as ip directed broadcast, if you configure ip helper-address, 'ip
forward-protocol udp' is automatically configured for you. Use it, if rtr1
is sending something else besides UDP
Hope that helps
Deepesh
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> yuki hisano
> Sent: Friday, May 16, 2003 10:10 AM
> To: ccielab@groupstudy.com
> Subject: ip broadcast-address
>
>
> Group,
>
> I still dont understand when to use "ip broadcast-address
> "command and when
> not to.
> What is the difference?
>
> Thanks!
>
> Yuki
>
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This archive was generated by hypermail 2.1.4 : Mon Jun 02 2003 - 15:13:44 GMT-3