debug ip packet rcvd explanation

From the Cisco Support Community, https://supportforums.cisco.com/thread/2111309

"rcvd 0" we've decremented ttl on input.  it's now 0 but it might be for us (like OSPF MCAST which is TTL=1 from begining)

"rcvd 1" not routing this, we're passing it to bridging code. might also see this even with bridging turned off (router config'd as an endstation)

"rcvd 2" can't route the packet. final check to see if it's for us. usually packets sent to this router where debug is done.

"rcvd 3" input & output interface is the same but we can't redirect
the packet for some reason (NAT maybe?) and it's not for us

"rcvd local pkt" it came from us originally, dropping

"rcvd 4" not sure, but looks like it's for us, just not the input
interface (one of the other ones) - loopback in you case.

"rcvd 5" can't route the packet, see if it's for us before dropping
not sure but this could be failure at the output interface such as
encapsulation failure

"rcvd 6" looks like for us if we have an IP alias entry due to NAT
or something.  Should jive with "show ip alias"

"rcvd 7" goes to one of our secondary IP addresses