Author Topic: Weird dhcp/routing issue  (Read 1048 times)

nswint

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Weird dhcp/routing issue
« on: March 07, 2008, 08:29:49 pm »
I lost all internal communication to the outside world this morning about 3 AM.  I thought this was strange because I could ping yahoo.com with no problem.  I discovered that something was up with routing on the internal network card.  It's been working fine for about 2 weeks and suddenly it's not working.
I'm setup as this
Cable modem
Wireless Router
External NIC
Core
Internal NIC
Switch
Computers

Internal network gets 192.168.80.1
External network get 192.168.2.205


Running tcpdump from the router I see very little traffic coming from 192.168.2.205 other than ntp traffic to canonical.com and arp requests from the router

I see tons of traffic from all of my computers with in the 192.168.80. subnet sending traffic directly to the router which it should not be doing

Nothing is coming directly from 192.168.80.1 or 192.168.2.205

Shouldn't dhcp issue the default gateway of 192.168.80.1 instead of 192.168.2.1?


Also shouldn't I be able to connect to connect via ssh from the router to the core if I have port 22 open on iptables?

orionsune

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Re: Weird dhcp/routing issue
« Reply #1 on: March 07, 2008, 09:06:42 pm »
Yes on all counts, you SHOULD be able to do all those things.

Answer me this, what is getting the 192.168.2.1 for it's gateway?  All the machines on your net? Or just the core's external nic?

Your setup is just going to require redundant forwarding for everything, obviously you've already figured this out, but every port you want opened/forwarded will have to be configured on the wifi router and the lmce box.  Instead I use this setup

Cable Model
Firewall Box
|Computer1
|Computer2
|LMCE <- One network card, DHCP disabled

And I rely on my trusty, proven reliable, firewall box of mine for my internet connectivity.

Really the firewalling and masqeurading options lmce gives you in the admin interface are basic at most... I found it kind of offending to network buffs myself...  To get the desired network behavior I wanted, I ended up writing my own firewall init script and trying to disable lmce's already built-in stuff, I eventually gave up,  so I definitely would not relay on lmce to be my gateway.

This is just my opinion!
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nswint

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Re: Weird dhcp/routing issue
« Reply #2 on: March 07, 2008, 10:39:17 pm »
just the core's external nic

nswint

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Re: Weird dhcp/routing issue
« Reply #3 on: March 07, 2008, 10:59:35 pm »
orionsune, Admins and power users:

What functionality would I miss out on if I turned off the dhcp functionality of the core other than automatic device discovery and pxe?

There appears to be a script that checks all the ips on the subnet, would that replace some of the device discovery?



orionsune

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Re: Weird dhcp/routing issue
« Reply #4 on: March 18, 2008, 09:08:08 pm »
Well this has been a HUGE debate between me and a bunch of other douche pickles, but to answer you question.  Not much.

You won't loose your automatic detection of network shares.
You will loose the ability to boot diskless machines, BUT, you can also configure your other dhcp server to point to the right location for serving the filesystem for the diskless machines.  This is only if your DHCP server is on a linux box and can accept versatile configuration like that.  Or if you have ssh access to your wired/wireless router, you can access your appliance based routers dhcp configuration that way also.  I suspect it's possible to reconfigure appliance based routers this way, ONLY if it uses embedded linux, I haven't actually tried, but based on my experience it's more than possible.

Other than those two most common functions you will loose the ability to automatically detect IP based phones like the cisco phone that can be used as an orbiter.  Any other IP based device that is not a file/storage sharing device will not be automatically detected.  But, if obtain some device like this with the intention of using it under lmce, you are mostly likely a slightly more advanced user and can handle the manual configuration of such devices.  If all you want is the remote file share ability, and maybe the media director ability, and already have a dhcp server/gateway you are happy with, then I highly recommend disabling DHCP on the lmce box, despite what these green star posters are saying.

That script, I saw also, was in StorageDevice_SambaRadar.sh, it's a pinging for loop.  It's only for network shares I believe.
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samisupidupi

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Re: Weird dhcp/routing issue
« Reply #5 on: March 19, 2008, 11:59:16 am »
hi orionsune
just a stupid question: i am trying to change the ip address of the eth0:0 device to an address in the range of my existing network, managed by an external dhcp server. (192.168.1.x instead of 192.168.80.1) i am trying the solution that you proposed in the other thread.

i changed the /etc/network/interfaces but when i restart the mce box, the internal ip (shown in the Advanced Menu) is still on 192.168.80.1. Where else than in interfaces do i have to change this address manually?

thanks for any help!
samuel

orionsune

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Re: Weird dhcp/routing issue
« Reply #6 on: March 19, 2008, 09:18:26 pm »
Change it in your webadmin panel of your linux mce box... just open a web browser and use the url

Code: [Select]
http://<your.lmce.box.ip>
Once logged in, on the top menu bar go over to Advanced, then down to Network, and over to Network Settings, change your ip address there.
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