[PLUG] Weird network problem

John Meissen john at meissen.org
Mon Oct 21 04:59:31 UTC 2013


> Thanks, Galen, for the help with my MythTV installation at the clinic 
> this afternoon.
> 
> When I got home from the clinic I started up the laptop, stopped the 
> Myth frontend, edited /etc/network/interfaces, deleting all those 
> comment signs in front of the static IP entries and putting on in front 
> of the DHCP entry. Then I ran MythTV Backend Setup and changed the IP 
> address in the General section to the static IP address of the machine.
> 
> However I was unable to see anything through the HDHomeRun.
> 
> After a bunch of fooling around I discovered that the laptop will not 
> see the Internet. I am able to ping the router, and other boxes in the 
> house, including the HDHomeRun. I can discover the HDHomeRun using 
> hdhomerun_config discover, but I can't get anywhere with Google Chrome 
> outside the house. I can see my internal web server, though.
> 
> Any idea what I've missed?

Sounds like multiple problems. 

You probably didn't set up a default route when you switched to static IPs. 
DHCP provides more than just the IP address, it also sets the nameserver and 
default routes. And then there's resolv.conf, or whatever they're using now
(<sigh> I just looked at my Ubuntu system, and resolv.conf is pointing to 
'localhost', and I've got something called 'dnsmasq' listening on that port).


You can still use DHCP and have static IP addresses. Edit the dhcpd.conf file 
to provide fixed addresses for those hosts you want, restart the dhcp server,
then let your systems use DHCP to set up networking. You can get the MAC 
address from 'ifconfig'.

When you say "I was unable to see anything through the HDHomeRun" what do you 
mean? Are you saying myth can't find your HDHomeRun? How do they get their IP 
addresses assigned?

Tweaking the DHCP server is a lot easier and cleaner than messing with and 
tracking fixed addresses the way you're doing it. Set it once and forget it, as 
long as the hardware (specifically the NIC) doesn't change it will always work 
right.

Set a subnet range for assigning to 'guest' systems that doesn't include the 
fixed IPs' you're assigning elsewhere:

subnet 192.168.10.0 netmask 255.255.255.0 {
 range 192.168.10.100 192.168.10.200;
}

Then set the addresses for your 'fixed' hosts:

host myth  { hardware ethernet 40:61:86:e4:1f:3b;
 fixed-address 192.168.10.10;
 option host-name "myth";
}

host hdhomerun  { hardware ethernet 00:18:dd:01:a1:9a;
 fixed-address 192.168.10.15;
}

(those are from my dhcpd.conf file)

While you're at it, set up a nameserver to resolve your local hosts, and keep 
it in sync with dhcpd.conf. Don't forget to specify it in the dhcpd.conf file:

option domain-name-servers 192.168.10.6

Of course, if you're using something like a linksys or dlink router to handle 
your dhcp you can still do all that, it's just different.

john-




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