You can adjust name resolution behavior in the Name Resolution section in the Preferences Dialog. Since Wireshark doesn’t wait for DNS responses, the host name for a given address might be missing from a given packet when you view it the first time but be present when you view it subsequent times. (e.g., 216.239.37.99 → Most applications use synchronously DNS name resolution.įor example, your web browser must resolve the host name portion of a URL before it can connect to the server.Ī given file might have hundreds, thousands, or millions of IP addresses so for usability and performance reasons Wireshark uses asynchronous resolution.īoth mechanisms convert IP addresses to human readable (domain) names and typically use different sources such as the system hosts file ( /etc/hosts) and any configured DNS servers.
Resolver to convert an IP address to the hostname associated with it Try to resolve an IP address (e.g., 216.239.37.99) to a human readable name.ĭNS name resolution (system/library service): Wireshark will use a name The same sort of thing can happen when capturing over a remote connection, e.g., SSH or RDP.ħ.9.3. IP Name Resolution (Network Layer) You might run into the observer effect if the extra traffic from Wireshark’s DNS queries and responses affects the problem you’re trying to troubleshoot or any subsequent analysis. As a result, each time you or someone else opens a particular capture file it may look slightly different due to changing environments.ĭNS may add additional packets to your capture file. The resolved names might not be available if you open the capture file later or on a different machine. Wireshark obtains name resolution information from a variety of sources, including DNS servers, the capture file itself (e.g., for a pcapng file), and the hosts files on your system and in your profile directory. The name is also not found in Wireshark’s configuration files. Unknown by the name servers asked, or the servers are just not available and
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