After installing Ubuntu Intrepid on my laptop, I got a nastygram from IT saying that my laptop was tripping alerts from their NIDS. They could tell me that it was an outbound SNMP request, but they couldn’t supply the OID or anything. Setting aside the fact that the NIDS should be configured to disregard SNMP requests for this particular OID, I set forth to try and figure out what the heck was causing the traffic. After much tcpdumping, I finally found the OID: 126.96.36.199.188.8.131.52.184.108.40.206. Googling told me that this OID corresponds to a printer name. At this point, I knew that it was coming from CUPS. Now, one would think that there is a simple on/off switch in CUPS that you could use to disable SNMP scanning. Nope! You can remove the snmp binary from the CUPS distribution, but the next time CUPS is installed/upgraded, you’ll be in the same boat. On a hunch, I edited /etc/cups/snmp.conf to look like so: #Address @LOCAL Address 127.0.0.1
Lo and behold, it worked! Instead of disabling SNMP scanning, I told CUPS to only scan the localhost IP instead of the entire local LAN subnet. After applying this change and restarting CUPS, I checked with IT. The NIDS alerts had indeed stopped generating alerts! Notes It turns out the snmp auto-detection stuff had been removed from previous versions of Ubuntu. After much bemoaning from users, the package maintainers put it back in place. This is why I have the issue on Intrepid and not on previous versions. I don’t really know what the optimal solution is here. The fact that my laptop was broadcasting SNMP requests to the entire corporate subnet is a little disturbing, if harmless. However I see where it would be nice to have in a SOHO environment. I personally would prefer a “disabled by default” approach with a very simple checkbox mechanism to enable it, but I’m certainly biased. Anyways, hope this helps some people out there. When I ran into this issue, Google didn’t have any help for me.