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Hostnames Overview

Almost all devices in your network have a hostname.

The hostname is the name that identifies the device on the network. A hostname is easier to remember than an IP address.

When you first power on a Juniper Networks router, switch, or security device, the default hostname is Amnesiac. The Amnesiac prompt indicates that the device is booting from a factory-fresh Junos OS software load. By definition, such a device doesn't have a hostname configured.

As an administrator, you follow conventions for naming devices. One such convention is to name the device based on its location—for example: germany-berlin-R1. Make the hostname unique within your local network so that users can connect to the device by using the hostname. You don't need to make the local hostname globally unique.

A device's hostname usually has a corresponding entry in the Domain Name System (DNS) so that you (the administrator) can connect to the device using the hostname. The fully qualified domain name (FQDN), which is used in the DNS, includes the hostname and the entire domain name. A period (or a dot) separates the hostname and the domain name labels, so the FQDN format is hostname.domain. For example, if the hostname is germany-berlin-R1 and the domain name is example, the FQDN is germany-berlin-R1.example. If the domain is registered and can be reached as on the Internet, the FQDN for the device is The FQDN is globally unique.

In Junos OS, the hostname can contain any combination of alphabetic characters, numbers, dashes, and underscores. No other special characters are allowed.

The software allows hostnames to contain up to 255 characters. Keep in mind that the total length of the hostname as an FQDN cannot exceed 255 characters (including the delimiting dots), with each domain name label having a maximum length of 63 characters. As a best practice, use short and meaningful hostnames, as long hostnames are difficult to type and to remember.