I am currently designing an interface for a network device, which needs to be configured by network admins. They are able to change the network settings (IP, subnet, gateway, dns), which got me thinking. After having configured countless devices, I am weary of having to enter the same stuff everytime.
So I built in some JS to make predictions. Assume we get the IP adress We now know:

  1. The subnet mask is most likely
  2. The default gateway must be somewhere in 192.168.1.
  3. The dns server is most likely somewhere in 192.168.1.

So after the user has provided the IP adress, I fill the other three fields with these values (the gateway and dns fields receive just 192.168.1.). If needed, the user can adapt the values.

My question is: Is that too much? Do professionals (target audience here) feel patronized with this approach? Or should I go even further and warn the user if he entered a mathematically wrong value (maybe as the subnet mask and as the gateway)?

  • Sometimes not doing anything is the best course of action. The thing is, people tend to "forget" to correct stuff that is already filled in for them (nngroup.com/articles/form-design-placeholders). They might assume that the given data is correct. One way to solve this problem is by allowing other methods of aqcuiring an IP address, for example, by using DHCP together with mDNS and/or LLMNR, even if no DHCP server is available, an IP address can be aqcuired with APIPA, bootp, ... perhaps you can clarify the use-case a little bit, so we can better understand how we can help? – Xabre Sep 2 '15 at 18:00
  • @Xabre, you have a point there... Towards the automatic IP acquisition - due to some platform specifics, clients must provide static IP configuration to make sure it will work in any network environment. However, I don't trust all of them to configure it correctly, which is why I even bother with this... – Moritz Friedrich Sep 2 '15 at 18:04
  • 1
    You could also spin it around by letting one enter the IP address first, followed by a gateway and the DNS, after this you can generate a valid and working subnet mask. In most "simple" situations, you could assume that the DNS will be the same as the gateway and the other way around. This brought the amount down to at least 2 input fields that need to be filled in. However, as you said: also validate the input. You could do a quick test to see if the settings work, for instance, by pinging your company server by name or IP address. – Xabre Sep 2 '15 at 18:12


Increasing efficiency (the time it takes to perform a task) is one of the key aims of UX. This becomes particularly important in areas of the system that are subject to repeated usage (and yours is a classic case).

Winning the lottery once is better than not winning at all

What you suggest is already done by some systems that were designed by leading designers. For instance, Apple's calendar app sets some fields for you (the chosen calendar) and changes the end of a new event for you based on the start time:

New event screen on the iPhone calendar app

If you come to think of it, choosing one hour as default event length is rather arbitrary; but even if it applies to 5% of the cases, it will still save time than asking all users to set it explicitly.

The mental plan guard

Users approach such interface already having formulated a mental plan as to what to do and what to enter.

The fact that the fields are only populated once the IP address is filled results in 'motion' and will draw attention.

The chance for errors (either not noticing or not recognising the address correctly) is small, and you can actually argue that it will be smaller than the chance of entry error (a single recognition act should yield less errors than the entry of 10 digits).

What's more, without such defaults, the user would anyway have to type into the fields, so having a default there mean no extra effort (provided the value is selected upon focus so any keystroke will delete the populated value).

So altogether, this sounds like an excellent idea. I think that particularly because your users are experts (meaning more frequent usage) they will appreciate such feature.

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