Underscore in hostname windows

Thus hostnames are names that helps in identifying devices in a network. During the period when the standards were being laid for the valid and invalid hostnames , the common terminal interface was the keyboard of the Teletype TTY ASR Though its valid to use underscores it not a recommended practice.

The wikipedia link in your post states that Microsoft Windows and Android smartphones does not enforce the rule against using an underscore in hostnames. Non enforcement of this rule may result in problems because many systems reject such kind of hostnames. On further investigation on the issue, I came upon this wonderful post which I suppose clarifies the usage of underscore in hostnames:.

Your reading of the Wikipedia page is incorrect. It does not say that those systems use underscores, it says that they support underscores.

If the administrator of such a system was to use an underscore when configuring it then it's his own fault when it fails to interoperate with the rest of the world. Hostnames including the domain component s are only allowed to contain alphabetic characters, numeric characters, hyphen and period. The wikipedia article linked in the question says that Android and Windows allow the use of hostnames which violate this syntax. Such names are definitely invalid hostnames but they are explicitly valid DNS records, even if they are address records which typically contain hostnames.

I don't know of an example of a hostname in the wild which uses underscores. Why is this allowed? As explained in the "Name Syntax" section of RFC , DNS intended to be a generic naming service so it doesn't try to enforce all the different name syntaxes that might apply to individual record types.

So even though underscores are disallowed in hostnames, the question of whether a program should allow them is more subtle. If you are setting the hostname of a particular machine, they should definitely be disallowed because they are invalid. If you are using a hostname, say to access a URL, I guess you could argue that you should allow it if it resolves, in an effort to "be liberal in what you accept".

There is this list from the WayBack machine, but it may not be accurate any more. The underscore whilst apparently allowed does not conform to the appropriate rfc regarding allowable characters and could raise incompatibility issues if used outside the local environment. Stack Overflow for Teams — Collaborate and share knowledge with a private group. United States English.

Ask a question. Quick access. Search related threads. Remove From My Forums. Asked by:. Archived Forums. Improve this question. Rook Rook 2, 5 5 gold badges 26 26 silver badges 34 34 bronze badges. Is this not a reasonable question? I didn't downvote, but I would've if I weren't out of votes. The way you phrased the question it sounds like you think there are some specific, well-known hostnames with underscores that all Windows systems use. Ward: yes, that's what the Wikipedia article implied, and it could have been true.

I don't think it was unreasonable to ask. I've rephrased the paragraph in question on Wikipedia. Hopefully it is clearer now. Show 1 more comment. Active Oldest Votes. Improve this answer. Community Bot 1. Fiasco Labs Fiasco Labs 4 4 silver badges 10 10 bronze badges. DNS records with underscores shouldn't cause any problems with domain transfers as they have always been legal DNS entries.

In other words, a telnet client might legitimately refuse to connect to a host whose name had an underscore, but if it doesn't do so, the DNS should be able to handle the name perfectly well. You might want to qualify answers like this.

Sorry; I overspoke. There's nothing improper about DNS server software refusing to accept A or CNAME records with underscores, so you might indeed run into trouble with zone transfers in this situation. But there's nothing improper about DNS server software accepting these records either. My point is that this isn't a proprietary or non-standard extension to DNS as your second paragraph claims, it's just a differing implementation.

I'm not sure under what circumstances you'd run into trouble with access points, could you expand on this?