being unknown you cannot you should use a sniffer capture instead.
the only fatal error a provider could do nowdays is to change your access from IPv4 to ipv6.
Or you are under a DOS attack with forged packets (but they must be routable so at least the ip header exists in this case debug ip packet if the unknown rate is not high can be used ) that can hit the router cpu.
I have noticed this issue as well with IOS 12.4(15)T7 and T8 on a Cisco 2811.
Here's the odd part though - those numbers ONLY seem to increase when I issue a show interface s0/0/0 command. I am SSH'd to the router. I will issue the command and see the unknown protocol drops count increase by one.
I have even issued the command once, then logged off after taking note of the number. I'll log on the next day, issue the command and notice that it only increased by one more number! It seems that they are not increasing for any other reason.
Well, I took a look a little further in to this matter and discovered that the FastEthernet interface connected to the local switch is showing a lot more of these unknown protocol drops. It sure seems like DTP is the cause.
I connect to the router over the WAN (a site-to-site VPN tunnel) to an IP assigned to the FastEthernet0/1 interface (connected to the switch), so in essence my SSH traffic is indeed traversing the S0/0/0 interface.
I agree that it's not causing any issues, it's just something I want to clean up.
I found this very helpful as I ran into this today. I have a 2821 running 124-15.T8 and have the same issue. I could not find any Cisco documentation on what protocol drops are. At least I know it is not anything to worry about. I ran the same test. I logged out of the router and logged back in 10 mins later and the numbers only incremented by 1. It seems the number increments only when I do the sh interface s/0/0/0:0. The errors show up on the LAN interface also.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...