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MediaMVP front-end & using your router's DHCP server
http://forum.linhes.org/viewtopic.php?f=6&t=4960		 Page 1 of 1
Author:  marc.aronson [ Sat Jun 18, 2005 9:49 am ]
Post subject:  MediaMVP front-end & using your router's DHCP server
I've found a way to successfully boot my mediaMVP myth front-end from my Knoppmyth server while still using my router's DHCP server for providing IP addresses for the other machines attached to my network. The approach is a kludge, but it works and it enables me to reboot my Knoppmyth box without taking down my DHCP server for the rest of my network.

At a high level I took advantage of the latency introduced by daisy chaining switches to ensure the Knoppmyth box's DHCP server would provide an IP address before my router's DHCP server did. It's worth nothing that I needed the daisy-chaining in my network for other reasons, and was not concerned with the nominal loss in network performance induced by this topology.

At a more detailed level, here is what I did:

1. Wireless router (netgear) has it's DHCP server enabled and provides IP addresses to everyone but the MVP box.

2. I connected a LAN port from the netgear router to a port on network switch#1.

3. I connected a port on network switch#2 to a port on network switch #1.

3. I connected the mediaMVP box and my Knoppmyth server into two available ports on network switch#2.

4. I configured my Knoppix DHCP server so that it would only provide IP addressed to the mediaMVP.

In essence, the two switches, which I have in my network for other reasons, introduce enough latency so that the Knoppix server always responds to the MediaMVP request before the Netgear DHCP server. A few more important notes:

1. It's worth nothing that what I've set up is a race condition in my network. There is no guarantee that the Knoppmyth box will beat the router in providing an IP address. One can envision scenarios where the Knoppmyth box is very busy and loses the race and the MediaMVP box wins the race and provides the IP address. Having said this, in 2-3 weeks of usage, with numerous reboots of the MVP deliberately induced, this has yet to happen.

2. I ran for a while without switch#2. (ie: Router connnected to swtich#1; MediaMVP box and Knoppmyth server connected to swtich#1). This also seemed to work reliably.

Below is a dhcpd.conf file that limits the linux server to only giving DHCP addresses to the MVP box. Don't forget to change the MAC address and domain name server addresses.

Code:
# my config file for dhcpd3 for Debian
# NOTE: I HAD TO COMMENT OUT THE FOLLOWING LINE
# FROM THE SAMPLE CONFIG FILE.
# ddns-update-style none;

# I left these values at default
allow booting;
allow bootp;
default-lease-time 604800;
max-lease-time 150000;

# basic subnet declaration, my router is at 192.168.0.1
# Since I am using the DHCP server on my router for all
# other address assignments, I have commented out the
# "range" line. If you want the linux box to provide IP
# addresses to other machines, uncomment and edit for the
# range of addresses you want served.

subnet 192.168.0.0 netmask 255.255.255.0
{
#  range 192.168.0.232 192.168.0.240;
  option routers 192.168.0.1;
  option domain-name-servers xxx.xxx.xxx.x, xxx.xxx.xxx.x;
}

# you then should give your MediaMVP a fixed IP number,
# and a filename to boot from. Note you will need
# to get the MediaMVP's MAC address from the sticker
# on the bottom of the unit
host MVP {
hardware ethernet 00:0d:fe:00:03:ae;
filename "dongle.bin.mvpmc";
fixed-address 192.168.0.230;
}


Hope this is helpful to others.

Marc
Author:  Zephrant [ Fri Jul 21, 2006 4:05 pm ]
Post subject: 
Neat hack-

I took a different approach- I installed tftpd on my firewall/dhcp server and have it serve up the dongle.bin file to the MVP, then tell it to go talk to the Myth box for files.

Mostly works, although I have one bug that makes me still have to manually point it to the Myth box after the first boot. I suspect I can fix that however.
Author:  iscraigh [ Sat Jul 22, 2006 10:44 am ]
Post subject: 
Not sure if this would work, but what about two nic's in the mythbox. Router connected to nic #1, MVP connected to nic #2 setup mythbox to only give dhcp to mvp. Then setup the Mythbox/gateway to not allow ports 67/68 to traverse the gateway. There is also a failover port 6 hundred something that you may also have to block.

Just a thought.

Craig
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