What is Dec MOP and how to disable it?
Performing a packet capture I keep seeing strange "DEC MOP Remote Console" frames:
No. Time Source Destination Protocol Info 141 83.557841 Cisco_57:62:a0 DEC-MOP-Remote-Console 0x6002 DEC DNA Remote Console Ethernet II, Src: Cisco_57:62:a0 (00:0d:bc:57:62:a0), Dst: DEC-MOP-Remote-Console (ab:00:00:02:00:00) Destination: DEC-MOP-Remote-Console (ab:00:00:02:00:00) Address: DEC-MOP-Remote-Console (ab:00:00:02:00:00) .... ...1 .... .... .... .... = IG bit: Group address (multicast/broadcast) .... ..1. .... .... .... .... = LG bit: Locally administered address (this is NOT the factory default) Source: Cisco_57:62:a0 (00:0d:bc:57:62:a0) Address: Cisco_57:62:a0 (00:0d:bc:57:62:a0) .... ...0 .... .... .... .... = IG bit: Individual address (unicast) .... ..0. .... .... .... .... = LG bit: Globally unique address (factory default) Type: DEC DNA Remote Console (0x6002)The source mac address is one from a Cisco router. However Decnet is disabled on the router and transport input set to telnet:
router# show decnet % DECnet is not enabled router# show run | begin line vty line vty 0 4 transport input telnetHow can I prevent this router to send these remote console frames?
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Decnet Maintenance Operation Protocol (MOP) is an ancient protocol that was used to administrate remote systems, and provided tools such as remote console or network bootstrap.
However, as of now this is still enabled by default on all Cisco IOS Releases from 9.0 to recent 15.x.
To disable MOP on the router it has to be done on a per-interface basis:
router# conf t router(configure)# interface fastethernet0/0 router(configure-if)# no mop enabled router# sh run int f0/0 | include mop no mop enabledMOP will be disabled even though the router still shows MOP as protocol on the interface:
router# show int f0/0 count prot status Protocols allocated: FastEthernet0/0: Other, IP, DEC MOP, ARP, CDP, IPv6DECnet MOP for some reason is still enabled in Enterprise trains. I've seen it get silently enabled after an IOS upgrade because it included a switch from advipservices. Unfortunately it is hard to get Cisco to change a default,
no ip directed-broadcasthas basically been the operator community's only success story (highest on my list to go is proxy arp).
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Content dated before 7/24/2021 11:53 AM
OzNetNerd 9 years ago
Just a quick FYI - the autosecure command disables MOP on all interfaces, amongst a lot of other things.