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Using the wired network in the Informatics Forum

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General usage guidance

In addition to our overall computing Policies and guidelines:

  1. Users should never interfere with network ports which are in use. Specifically, please don't unplug a network cable from a network port so that you can use that port for some other purpose: doing so is contrary to the Computing Regulations.
  2. Since it's important that an appropriate subnet is used for any particular machine, please don't arbitrarily connect a PC, laptop or similar device to any 'random' port not currently in use. If this document doesn't make clear the intended use of the port in question, or you're otherwise not clear about its intended use, please contact the Computing Support team.
  3. Please do not connect any networking equipment to any network port without asking for, and obtaining, prior approval. Doing so can disrupt the service for other users.
  4. Service-discovery protocols, such as mDNS (Avahi, Bonjour) will not work through our routers. If this is important to you, please ask Support to ensure that all your self-managed machines are on the same subnet.
  5. If you need clarification of network usage, or if you would like a network port reconfigured in some way, please contact the Computing Support team: they will be happy to help.

Subnets, VLANs and network ports

The School of Informatics has some 40 or so different IP subnets in use, each of which serves a particular purpose, and each of which is carried on a particular VLAN (i.e. a logical 'piece of ethernet'). In turn, each of the network ports you see around the building will - if active at all - have been configured to be on a particular VLAN.

It is important that an appropriate subnet is used for any particular machine. For example, in the Forum, laptops and similar devices which don't require a fixed IP address generally belong on the 129.215.90.0/23 subnet, which is carried on VLAN 'DHCP' - so any such device must be connected to a network port which has been configured to be on VLAN 'DHCP'.

Machines on the 'wrong' subnet might just not work at all and, even if they do, they probably won't acquire their expected IP configuration.

Normally, end users don't have to worry about the configuration of network ports to VLANs: the Computing Support team takes care of that. But knowing the subnet-to-VLAN mapping is useful, and helps to make sense of the information returned by the search facility on our Informatics Forum network monitoring page.

Further information

Last reviewed: 
18/10/2017

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