Fixed IP

Vincent Kars

WBF Technical Expert: Computer Audio
Jul 1, 2010
860
1
0
Today a lot of audio gear (music servers, headless PCs, Squeezebox, Sonos) are remote controlled.
No, not by a IR remote (the ones you have to point) but a iPhone, iPad, smartphone, etc. in other words over the (W)LAN ( (wireless) home network ).

As you can understand, each device in a network most have a unique IP address pretty much like each telephone number must be unique.
This is in general done by the router using DHCP (Dynamic Host Configuration Protocol)
Next time you power up a device it in general gets the same address.
This is because the router memorizes it. But is does so for a limited time.
This period is called the lease. If this period is expired a new IP address is generated.

Most of the time you can refer to a device in the network by name.
But not all of the time. Often you are forced to use an IP number.

Al of a sudden your remote won't find your music server anymore.
This is because the lease has expired.
In this case a fixed IP address is very convenient.
If you use port forwarding (assessing a device in the LAN over internet), it is a must.

Most devices allow you to set a fixed IP address on the device it self.
If this device is off for a prolonged period, it might happen that DHCP assigns this IP address to another device. On power on, you have two devices with the same IP address in your network. As usual, it takes a whole weekend only to find out that an IP conflict is the cause of your network problems.

If you set the fixed IP on the router, DHCP knows this address is reserved for a specific device so it won't be assigned to any other device.
This is done by coupling the IP address to the MAC (Media Access Control ) address of the network card of the device. Each network card has a unique hardware address.
If a device has wired and a wireless network connection, it will also have 2 different MAC's.
DHCP will assign 2 different IP addresses to them.

Best practice is to use a fixed IP only when needed.
If needed set it on the router.
If you do have to set in on the device, use a number outside the range normally used by DHCP.
 

amirm

Banned
Apr 2, 2010
15,813
38
0
Seattle, WA
Nicely explained! On the last line, you can tell the router not to use certain range of IP addressed which you can then reserve for manual assignment.
 

Vincent Kars

WBF Technical Expert: Computer Audio
Jul 1, 2010
860
1
0
Indeed you can tell a router the range to use.
But a lot of people don’t know this.
But even if you do, you might erroneously give two devices the same number outside this range.
I do think it is safer and more convenient to do the whole administration on one single spot, the router doing the DHCP in your home network.
 

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