Cisco Switches Constant DNS Resolution of cisco.com and www.cisco.com

[cameron_r17]

So, I set up our own DNS server for our house. I can see the logs of all of the DNS queries. Also, we use a service from Cloudflare to visualize the DNS queries. Our house has two Cisco switches: CISCO DESIGNED CBS250-8T-D Smart Switch and CISCO DESIGNED CBS220-24T-4X Smart Switch. Basically, there are constant DNS resolutions to cisco.com and www.cisco.com. In an hour, we have around 12,000 DNS queries in total. 5,000 of those queries are to cisco.com, and 3,000 of those queries are to www.cisco.com. This means the switches are generating more DNS queries than the rest of our network combined. I'm wondering why this is happening. I've attached the graphs.

[Georg Pauwen · Accepted solution]

Hello,

odd. What if you add a host mapping for cisco.com ?

https://www.cisco.com/c/en/us/td/docs/switches/lan/csbms/CBS_250_350/Administration-Guide/cbs-250-ag/cbs_250_chapter_16.html#ID-00004d3d

[cameron_r17]

Maybe I didn't come up with the best solution, but I just ended up disabling DNS on the switches. For some reason, disabling Bonjour helped to get rid of some queries. After that, the switches were only resolving time servers, not cisco.com. I have a time server on my LAN, so I'll just point them to that server because they won't be able to reach public time servers without DNS. But yes, very strange. 

Host mapping did work. But, I feel like host mapping wouldn't solve the root of the problem because the switches would still be making a large number of requests to cisco.com. It's not that it takes up a lot of bandwidth, but it is for sure a lot of extra noise on the network for no good reason. Thank you for your support!!