Name resolution tries to convert some of the numerical address values into a human readable format. There are two possible ways to do these conversions, depending on the resolution to be done: calling system/network services (like the gethostname() function) and/or resolve from Wireshark specific configuration files. For details about the configuration files Wireshark uses for name resolution and alike, see Appendix B, Files and Folders.
The name resolution feature can be enabled individually for the protocol layers listed in the following sections.
Name resolution can be invaluable while working with Wireshark and may even save you hours of work. Unfortunately, it also has its drawbacks.
DNS may add additional packets to your capture file. 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.
The same sort of thing can happen when capturing over a remote connection, e.g. SSH or RDP.
Name resolution in the packet list is done while the list is filled. If a name can be resolved after a packet is added to the list, its former entry won’t be changed. As the name resolution results are cached, you can use → to rebuild the packet list with the correctly resolved names. However, this isn’t possible while a capture is in progress.
Try to resolve an Ethernet MAC address (e.g. 00:09:5b:01:02:03) to to a human readable name.
ARP name resolution (system service): Wireshark will ask the operating system to convert an Ethernet address to the corresponding IP address (e.g. 00:09:5b:01:02:03 → 192.168.0.1).
Ethernet codes (ethers file): If the ARP name resolution failed, Wireshark tries to convert the Ethernet address to a known device name, which has been assigned by the user using an ethers file (e.g. 00:09:5b:01:02:03 → homerouter).
Ethernet manufacturer codes (manuf file): If neither ARP or ethers returns a result, Wireshark tries to convert the first 3 bytes of an ethernet address to an abbreviated manufacturer name, which has been assigned by the IEEE (e.g. 00:09:5b:01:02:03 → Netgear_01:02:03).
Try to resolve an IP address (e.g. 216.239.37.99) to a human readable name.
DNS name resolution (system/library service): Wireshark will use a name resolver to convert an IP address to the hostname associated with it (e.g. 216.239.37.99 → www.1.google.com).
Most applications use synchronously DNS name resolution. For example, your web browser must resolve the host name portion of a URL before it can connect to the server. Capture file analysis is different. A given file might have hundreds, thousands, or millions of IP addresses so for usability and performance reasons Wireshark uses asynchronous resolution. Both 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.
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.
You can adjust name resolution behavior in the Name Resolution section in the Preferences Dialog. You can control resolution itself by adding a hosts file to your personal configuration directory. You can also edit your system hosts file, but that isn’t generally recommended.
Try to resolve a TCP/UDP port (e.g. 80) to to a human readable name.
TCP/UDP port conversion (system service): Wireshark will ask the operating system to convert a TCP or UDP port to its well known name (e.g. 80 → http).