hashicorp/vagrant · error · Vagrant::Errors::NetworkCollision

The specified host network collides with a non-hostonly netw

Error message

The specified host network collides with a non-hostonly network!
This will cause your specified IP to be inaccessible. Please change
the IP or name of your host only network so that it no longer matches that of
a bridged or non-hostonly network.

Bridged Network Address: '%{netaddr}'
Host-only Network '%{interface_name}': '%{that_netaddr}'

What it means

For IPv4 private networks, the action computes the host-only subnet (netaddr) and compares it against the network address of every bridged (physical) interface from read_bridged_interfaces. If they are equal and the interface status is not 'Down', it raises NetworkCollision: routing would send host-only traffic out the real interface, making the configured IP unreachable.

Source

Thrown at plugins/providers/virtualbox/action/network.rb:336

            raise Vagrant::Errors::NetworkAddressInvalid,
              address: options[:ip], mask: options[:netmask],
              error: e.message
          end

          validate_hostonly_ip!(options[:ip], @env[:machine].provider.driver)

          if ip.ipv4?
            # Verify that a host-only network subnet would not collide
            # with a bridged networking interface.
            #
            # If the subnets overlap in any way then the host only network
            # will not work because the routing tables will force the
            # traffic onto the real interface rather than the VirtualBox
            # interface.
            @env[:machine].provider.driver.read_bridged_interfaces.each do |interface|
              that_netaddr = network_address(interface[:ip], interface[:netmask])
              if netaddr == that_netaddr && interface[:status] != "Down"
                raise Vagrant::Errors::NetworkCollision,
                  netaddr: netaddr,
                  that_netaddr: that_netaddr,
                  interface_name: interface[:name]
              end
            end
          end

          # Calculate the adapter IP which is the network address with
          # the final bit + 1. Usually it is "x.x.x.1" for IPv4 and
          # "<prefix>::1" for IPv6
          options[:adapter_ip] ||= (netaddr | 1).to_s

          dhcp_options = {}
          if options[:type] == :dhcp
            # Calculate the DHCP server IP and lower & upper bound
            # Example: for "192.168.22.64/26" network range those are:
            # dhcp_ip: "192.168.22.66",
            # dhcp_lower: "192.168.22.67"

View on GitHub (pinned to 35f3160f4a)

Solutions

1. Change the private_network ip (and/or netmask) to a subnet no physical interface uses, e.g. 192.168.56.x or 172.28.x.x
2. List candidates first: `VBoxManage list bridgedifs` (or ipconfig/ifconfig) and pick a free subnet
3. Disconnect/disable the colliding interface (unplug dock, disable VPN) if it must not participate
4. In shared environments, document the reserved Vagrant subnets so teams do not collide

Example fix

# Vagrantfile - before (host LAN is 192.168.1.0/24):
config.vm.network 'private_network', ip: '192.168.1.50'

# after:
config.vm.network 'private_network', ip: '192.168.56.50', netmask: '255.255.255.0'

require 'ipaddr'
def collides_with_bridged?(desired_ip, netmask)
  desired = IPAddr.new("#{desired_ip}/#{netmask}")
  `VBoxManage list bridgedifs`.scan(/IPAddress:\s+(\S+).*?NetworkMask:\s+(\S+)/m).any? do |ip, mask|
    IPAddr.new("#{ip}/#{mask}") == desired
  end
end
abort 'subnet collides with a bridged interface' if collides_with_bridged?('192.168.1.50', 24)

begin
  env.cli('up')
rescue Vagrant::Errors::NetworkCollision => e
  warn "Host-only #{e.extra_data[:netaddr]} collides with #{e.extra_data[:interface_name]} - pick another subnet"
end

When it happens

Trigger: `vagrant up` with `config.vm.network 'private_network', ip: 'x.x.x.y'` where x.x.x.0/24 (given the netmask) equals the subnet of a connected physical NIC — e.g. laptop on a 192.168.1.0/24 LAN plus private_network ip '192.168.1.50'.

Common situations: Corporate/home LANs on 192.168.1.x or 10.0.0.x colliding with common Vagrant example IPs; docking/VPN adapters appearing after the Vagrantfile was written; CI hosts with many bridged NICs.

Related errors

• The specified host network could not be found: '%{name}.' If
• NFS requires a host-only network to be created. Please add a
• Network settings specified in your Vagrantfile define an inv
• The IP address configured for the host-only network is not w
• Could not find a required VirtualBox guest property: %{gue

AI-assisted analysis of hashicorp/vagrant@35f3160f4a (2026-08-21). Data as JSON: /api/errors/3348b7dc9119b246. Report an issue: GitHub.