07-03-2003 02:33 AM - edited 03-02-2019 08:36 AM
Hi,
I'm a CCIE but I'm still dump. :)
Under which conditions does a router forward a packet destined for 255.255.255.255?
Regards
Alex
07-03-2003 06:38 AM
Alex,
By default every router blocks or drops broadcasts. If you configure a helper address, That should help forwarding broadcasts received on a particular interface to another network.
07-03-2003 09:38 AM
Or apparently in some earlier versions of IOS the router would forward these packets by mistake due to a bug , just saw this the other day on 11.0.17 code where a device was answering to broadcast yet the traffic was able to get off the subnet to it's destination .
07-07-2003 11:43 AM
Alex,
There are such things as directed and undirected broadcasts. a message sent to 255.255.255.255 should not traverse the subnet it's on. However, this is not so with a bad IOS or an IP Helper statement (it gets a little more complicated but, we'll save that.). A directed broadcast is one that is sent to a different subnet, but the subnet is specified. I'm sure the guys will correct me if this is incorrect. So a directed broadcast would be such that subnet A is 10.0.1.0/24 and subnet B is 10.0.2.0. A client on subnet A sends a broadcast to the IP 10.0.2.255 it should be forwarded. I hope this helps.
-Bo
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