[c-nsp] Loopback IP set to .255 - 6500 responds to ICMP echo-request from wrong interface

[Jay Hennigan]

On 12/31/11 9:33 PM, Eric Rosenberry wrote:
> I am scratching my head here wondering if I have run into a Cisco bug, or
> somehow intended weird behavior...
> 
> I set the loopback IP's for a pair of 6500's (Sup720-3CXL's) to adjacent
> IP's and have *identical* config's on them (sans their interface and
> loopback IP's).
> 
> One of them is 216.x.x.254 and the other is 216.x.x.255.

If the mask of 216.x.x is /24 or longer, then .255 will be a broadcast
address and the ping response will be from one or more host addresses on
the subnet.

If the second x of 216.x.x is odd, then the same issue will pertain to
shorter masks, binary math will tell you which.

--
Jay Hennigan - CCIE #7880 - Network Engineering - jay at impulse.net
Impulse Internet Service  -  http://www.impulse.net/
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