We know the source, it is a Mikrotik routerboard. We are expecting to see these packets. The issue is that the packets contain invalid data - the data is valid leaving the device and invalid when received so the perceived issue is somewhere between the C5X and A5C.
MT1 = Mikrotik Router 1 (where broadcast packet is originating)
MT2 = Mikrotik Router 2 (where broadcast packet is received)
MT1 <-ethernet-> C5X <-wireless-> A5C <-ethernet-> Cisco Switch <-ethernet-> MT2
Show CDP Neighbors detail on Cisco Switch shows:
Device ID: [John Doe]
IP address: 192.168.1.162 - [this is showing correct here, modified for obv reasons]
Platform: MikroTik, Capabilities: Router
Interface: GigabitEthernet0/24, Port ID (outgoing port): ether1
Holdtime : 117 sec
advertisement version: 1
Power Available TLV:
Power request id: 0, Power management id: 0, Power available: 0, Power management level: 0
But on MT2 it is showing up malformed. Not sure if CDP uses the source IP vs Mikrotik Discover Protocol using IP from data in packet. Will do some more homework and post any results I find!