[rescue] Static IP! Now what?

Phil Stracchino phils at caerllewys.net
Thu Apr 6 09:54:15 CDT 2017

On 04/06/17 09:20, John Hudak wrote:
>> What else is a static IP good for?
> Many ppl have already responded with good points.  I just want to point out
> a subtly of the overloaded term 'static IP address'...
> Static means that the IP address of the device itself does not change.  The
> subtly is where it gets the assignment from.
> In the 'bad old days'  device IP addresses were manually assigned and
> configured on the client device. The evolution of routers provided a
> capability called 'reservation tables' in which the user specified in the
> router configuration:  the MAC and the associated desired LAN IP address.
> This arrangement provided the outward appearance of a static IP address but
> it was managed by DHCP.

Commonly known as a "static lease".  Almost any consumer router can do 
it, including the EdgeRouter Lite[1] you're using.

>  Depending on your computing environment, this
> arrangement offers many of the advantages of manually assigned/managed
> static IP addresses.  There are some drawbacks, some of which are the
> router becomes a single point of failure, increased 'boot time' of a large
> network and access to the router to see the assignments.
> The two types of IP address management approached can coexist on a network
> but configuration and operation of the network can become a little
> complicated...that's a topic of another much longer discussion.

It's really not difficult at all.  Just allocate separate static and 
dynamic IP ranges.  For instance, on my networks, DHCP is allowed to 
dynamically allocate .100-.254 in each subnet.  All addresses .99 and 
below are statically assigned, either on the device or as static leases.

[1]  Word of warning:  The EdgeRouter Lite is fine.  The EdgeRouter 
POE-5 is fine.  All the larger ones are fine.  Perfectly good devices. 
DO NOT buy the EdgeRouter X.  It is so starved for storage it can't even 
apply an OS update without deleting the old image *FIRST*, which I think 
we can all agree is a recipe for disaster.  You can still recover from a 
failed upgrade by doing a factory reset, but that of course erases all 
of your configuration and data[2].  It will run out of storage in a 
couple of weeks if you even just turn on logging without activating any 
functions not enabled out-of-the-box.

[2]  If you dig around for it on Ubiquiti's web site, you will find 
procedures to enable backing up EdgeOS device configuration to an 
external host via ssh or rsync.  It's a really good idea to do so.  It 
can save you a lot of frustration.  If you install any additional Debian 
packages whose configuration is *not* managed by EdgeOS, you'll have to 
back up their configuration manually.

   Phil Stracchino
   Babylon Communications
   phils at caerllewys.net
   phil at co.ordinate.org
   Landline: 603.293.8485

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