3 DHCP in same network

[cyf4746]

I have a Belkin router as my 1st DHCP server, a PC box as my 2nd DHCP server for other applications. All workings find. Now I installed LMCE and this will be my 3rd DHCP server on the same local network. My 2nd DHCP server not working after I installed LMCE. I suspect it is the network setting for LMCE (3rd DHCP server) which caused the problem.
Please help me.....

[tkmedia]

You should only have 1 dhcp server on any 1 network segment.
The Lmce box should be that dhcp server.



Tim

[jimmejames]

I have 3 as well, but I cascade them-
cable modem goes to first dhcp serving router
    |->  LMCE core plugs into one port- serves XX boxes throughout house
    |->  WAN port on second router plugs into another port and serves few other boxes in house

Note- both LMCE and second router are only serving addresses down the pool- not up.  The second router is not trying to give LMCE an addess and LMCE is not trying to give the second router an address.


YES all of this could be done with LMCE as the first dchp server and turn the dhcp serving setting off on the other two routers.  I don't because 1) I don't trust/understand the LMCE firewall  2) when static IP addresses were setup on NAS's, skype phone, etc my LMCE builds would last about a week and I haven't taken the time to reconfigure the system with LMCE first...

[colinjones]

Echo tk's remarks - you should only ever have 1 DHCP server on any one segment (broadcast domain). If you had 2, then they definitely were not working properly, they would have been fighting each other, even if you didn't realise it. You definitely cannot have another DHCP server on the LMCE's internal network, it simply will not work. See here - http://wiki.linuxmce.org/index.php/Network_Setup

[Govo]

If you have three on the same network , make sure you DONT RUN the setup diskless  md on the   Wizard | Media Directors.

Have three dchp networks which linux mce is on the second and i have no problems once i dont run the above , it seems that when you run the above it takes over the network for some reason .

so what i have done is ran the above and block the out going connection to the router so that it only receives the incoming connection and the hook up a second nic card for my mds and everything is working fine ,


Gov

[colinjones]

As I said, you cannot run more than one DHCP server on the internal network, LMCE needs to be the sole DHCP server. Otherwise you will have no control over which DHCP server responds to a client.... when the wrong one responds, pnp will not work, nor will MD detection/creation/booting. Whichever one responds you will likely end up with conflicting IP addresses. If the DHCP servers are on separate networks then this is not relevant.

Nobody should be using the Setup Diskless MD wizard in the admin site, this is a legacy. The correct way of setting up an MD is -> 1) turn on PXE, 2) reboot machine ... done, the core does everything else automatically.

[jimmejames]

Maybe I'm misunderstanding what cyf4746 was asking originally, but it's still not clear why running any number of router/switches/hubs before connecting to LMCE's WAN port makes any difference.  Isn't this exactly what ISPs do from some backbone to your local connection?  Why would LMCE care if it is getting an IP address from your ISP vs from your router?

Understandably, yes, there should be no DHCPs downstream of LMCE, but upstream or even level with LMCE?  The only way I can see that there would be an issue is if your DHCP servers were serving ip address on both the LAN ports and the WAN port.  And in what cases would you want a router that servers a ip addess on the same port that it gets its ip other than if you're trying to setup LMCE as a 1 nic setup?  I've been running the same setup since the first LMCE video was posted on digg (2 years ago) and if the routers are fighting I have yet to notice any effects on bandwidth or ip address assignment.

Without a doubt, if you're new to LMCE (or hope to get support from the forum) get a system with 2 nics and make LMCE the first in line for your local network and disable all other DHCP servers.

[totallymaxed]

Maybe I'm misunderstanding what cyf4746 was asking originally, but it's still not clear why running any number of router/switches/hubs before connecting to LinuxMCE's WAN port makes any difference. 

As Colin said...you can have as many routers/switches/ etc etc on WAN side of the Core as you would like.... but anything on that side is 'outside' of the LinuxMCE Core's LAN side Network.

The outside world is on the WAN side of the Core... yes you can have a router there acting as a DHCP server... it can even offer DHCP addresses to the WAN side NIC of the Core...as it would any other device on that WAN side network. The Network on the WAN side of the Core is on its own so to speak.

Andrew

[jimmejames]

Thank you Andrew-  that was exactly what I was saying in my first post in the thread, but started second guessing myself after some of the other posts...