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

[Eric Rosenberry]

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.

When pinging the loopback IP's of these devices from the Internet, one
responds as expected (from the IP of the loopback), and the other (.255)
responds from a *different* IP address (one of it's interface IP's rather
than the loopback IP).

I am guessing there is some different code path being exercised here
because .255 is normally the broadcast address in classful networking?
 Somehow the router trying to avoid "directed broadcast" or something?

I am running code rev: 12.2(33)SXI3

ip classless is enabled.

Any thoughts?

P.S.  Changing the router that is .255 to .253 makes it work as expected.
 I am probably just going to make 216.x.x.252/30 into a routing subnet and
move the routers back to .250 and .251...

-Eric

-- 
*Eric Rosenberry*
Sr. Infrastructure Architect // Chief Bit Plumber

Direct: 503.943.6763
Mobile: 503.348.3625 // XMPP: eric.rosenberry at iovation.com
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