Wireless routers

Access

The Nevis particle physics group maintains several wireless routers throughout the upper portion of the Nevis site. They are all protected by an access code, which is displayed on the doors to student rooms in the research building (including room 115, the library) and on small signs located throughout the Mansion house.

Networks

The current networks associated with the particle-physics group are:

Name Location
nevis-research-building research building
NETGEAR-elec electronics building, lower floor
nevis-mansion-house Mansion house, first floor and portions of the second floor

The NETGEAR networks come in two flavors: running at 2.4 GHz, with a maximum throughput of 130 Mb/s, and 5 GHz, with a maximum throughput of 300 Mb/s; the latter flavor has "-5G" appended to the network name. However, as of May-2010, the routers are connected to 100 Mb/s network switches, which means you won't see the maximum wireless speed. For now, the choice between the flavors is largely arbitrary; however, the 2.4G signal strength will probably be greater.

You may see other network names than the ones listed above, probably without password protection. Those were set up by other research groups. Please do not use them.

Wired versus wireless

As noted in the discussion of the Nevis particle-physics networks, the wired connections in most Nevis offices connect to the private network, while the wireless connections connect via the sandbox network.

The practical differences between using the two networks:

  • The wireless network does not have a default domain. The command ssh hogwarts will work while on the wired network, but it's necessary to type ssh hogwarts.nevis.columbia.edu while on the wireless network.

    To get around this, you can set a default domain in the network settings on your laptop. The procedure varies between Mac, Linux, and Windows; look around the Network settings control panel, under DNS.

  • The Nevis network services are not available on the wireless network, at least no more than they would be to anyone trying to access from outside Nevis:
    • You can't mount disks via NFS or automount
    • You can't browse for printers using CUPS
    • Machines on the private network are invisible to the wireless sandbox network.

Mansion house

The wireless network in the mansion house connects to the network in the research building via a wireless bridge. The maximum speed of this bridge is 54 megabits per second (802.11g). It can be slower if there are obstacles between the buildings; e.g., rain, snow, tree branches blown by the wind. Given the bandwidth limitation, please be considerate of other users in the mansion house if you need to download large files or stream video.

Network details

Each wireless router has its own IP address, and each is its own separate DHCP server. They have been configured so that if a wireless router has the address 10.43.2.N, the DHCP addresses it offers are in the range 192.168.N.XXX, where XXX is from 2 to 100.

The purpose of this arrangement is to make it easier to find out which wireless router your laptop is using. For example, if your laptop has been assigned the IP address 192.168.5.4, then it's getting its wireless signal from the router at 10.43.2.5 = wireless-library.nevis.columbia.edu, the wireless access point in the Nevis library.

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Topic revision: r6 - 2015-10-07 - WilliamSeligman
 
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