Dual homed host

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A dual homed host ( DHH ) is a host that is located in two network environments . This usually means that it has IP addresses from at least two networks.

The DHH can be reached from both networks, but does not establish a direct network connection between the networks and, in particular, does not forward packets from one network that are intended for the other network.

The DHH process has several purposes:

  • Separation between user network and administration or backup network for reasons of security or performance .
  • A server can be configured dual-homed in order to be able to respond differently to accesses from two different networks, e.g. B. if requests from the local network are to be treated differently than requests from the Internet . This can also happen for other intentions, for example for reasons of computing power .
  • Instead of a firewall , which has the purpose of only routing defined packets from one network to the other, the routing can also remain completely deactivated. Users in one network who want to send packets to another network must then, e.g. Log on to the DHH, for example via Telnet or Secure Shell , and start the program that is to have access to the other network from this computer.

If the two networks are separated by a firewall, when configuring the DHH it should be ensured that response packets are sent back on the same network interface on which they were received. This is impossible if a sender has to address both DHH addresses with only one IP address, since the return routing is based on the sender IP, which is always the same.

The term is not part of an RFC or an Internet standard and is used almost exclusively by experts .

See also

Individual evidence

  1. Claudia Eckert : IT Security: Concepts - Procedures - Protocols . De Gruyter, Berlin 2018, ISBN 978-3-11-055158-7 , pp. 735 ( limited preview in Google Book search).