[RndTbl] home network hangs up when ISP diconnected

c0l0nelFlagg mashfiend at gmx.com
Mon Nov 21 21:42:02 CST 2016

My apologies for the previous reply post to ask this new question.

I have a home network that appears to stop working whenever the ISP 
connection to the outside world is dropped. I am not sure why or how to 
remedy it which is why I am posting here.

I have 5 linux workstations on the internal network 3 MINT 18, 1 
XUbuntu, and 1 UbuntuStudio  all the latest versions. 3 of the 
workstations (all MINT ones dual boot to Win 7 Pro as well). I also have 
a dedicated Ubuntu server on the network (also the latest Ubuntu version).

The ISP connection (being in a rural area) is a cellular voice/data hub. 
The data connection from the hub feeds the hot or RED NIC input to the 
dedicated firewall machine Smoothwall Express. The GREEN or LAN side 
output from the Smoothwall machine then feeds a couple of Gigabit 
Ethernet smartswitches connecting to the network workstations, server, 
and smart TV's and Canon MP620 networked printer.

The Smoothwall dhcp server capabilities are set up to assign IPv4 
addresses to each permanently connected LAN device with a reserved IPv4 
address based on the device's MAC address.

All network devices have the Smoothwall specified as the 1st dns address 
as well as gateway device. The second dns device is the IPv4 address 
assigned to the ISP voice data hub which is the gateway for the 
smoothwall machine. A third alt dns address is Google's public dns at

Under normal serviceable connections, all is well, however if I lose the 
ISP connection everything running linux appears to get bogged down as if 
it was waiting for long timeouts of some sort; and if win 7 Pro is 
running the IP address assigned to the NIC's in those machines get 
changed from the initially assigned class C address to the default 
windows 169 series and of course the networking quits working on them as 

What I am trying to find out is if the smoothwall is acting as a local 
dhcp server, a local dns caching server as well as the gateway why is 
everything grinding to a halt whenever the ISP connection goes down? and 
what I can do to prevent it from stopping functions in the future.

All machines have full local network addresses specified in hosts, 
host.sam files and the order of precedence is to resolve using those 
files first then dns.

When ISP connection is down the linux boxes are all able to see the NFS 
shares by using the host file info but samba and windows boxes just go 
south for some reason.

Any tips or help is appreciated.

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