default gateway intermittent

[ordisecours]

I wrote this message tonight, I will try to give you a snapshot of our system at work,

we have 3 buildings (avg of 15 computers each); building #1 is a car showroom departement, building #2 is a mechanic departement and building #3 is our head office and server and internet access router,

Since a month , problem begin one day in building 2, no internet access, on 1 computer, ; this computer was having access to all other software on server, BUT NO INTERNET ACCESS... AFTER ANALYZE AND CHECK the default gateway was xxx.xxx.192.8 instead of xxx.xxx.192.7 ???

all of our 45 PC is on dhcp automatic, our end router is at xxx.xxx.192.7

I desactivate the NIC card, wait 15 sec. and reactivate that was ok.

since, 5 other PC in building 2 or 3 or 1 has lost different day the default gateway ...

never two together, all in intermittent days and hour of the days.

After speaking with the hardware support(A) and softare support(B) ( 2 differents company) (A) say (B)is default and (B) say (A) is default like usaually i'm alone in my jungle.

I know my post is long , thanks to read, I'M on vacation right now , and can't leave that problem on the job...

If you have tips or trick or ANSWER for me , it will be greatfully accept.



..._ - _ - every trouble shooting begin with power ON !! we always forgot one day. HAVE A NICE DAY.

 

[ordisecours]

Sorry just a clue maybe, this network was operational since OCTOBER 2006

No other probleme since



..._ - _ - every trouble shooting begin with power ON !! we always forgot one day. HAVE A NICE DAY.

 

[jdeisenm]

It sounds like the comptuters are getting there IP Address and gateway from a different dhcp server.

run the command ipconfig/all on a windows pc that is working.
run the same command on a computer that is not working. check the default gateway and dhcp server lines.

 

[ordisecours]

thanks jdeisenm,

I already check that, and thats how i found that incorrect gateway .8 instead of .7

The xxx.xxx.192.8 is a little router joining 3 pc in building 3, so my question is ... why in building 3 or 1 or 2 the defect pc , when it is happening see that router (.8) instead of the usually "major" router in head office

My big question is if it was the "major" router bugging some millisec , more than one PC will be "tilt" in error ???

and I say it again, one PC in one building each time and after resetting the pc, everything goes well for 3,4,5 days ...and another PC randomly in building 1,2 or 3 can have the problem

..._ - _ - every trouble shooting begin with power ON !! we always forgot one day. HAVE A NICE DAY.

 

[gdvissch]

if running ipconfig /all you should specifically look at which server is DHCP server for these machines that work and these that don't. As jdeisenm I also suspect, that both routers are acting as DHCP servers sending their own address as default gateway to clients.
If this confirms to be true, you can just stop DHCP on the "litlle router"

When you have 2 DHCP servers on a network, you can never surely tell which one will give an address to the clients. Depends on lease time, proximity to DHCP server, etc...

CU
G.

 

[gb0mb]

I am not sure how I would test on a windows box, but on linux I would do this.

Clear the arp table. Open a tcpdump on the interface and then ping the default gateway. Watch the traffic to see who is sending arp replys back to the system. If you see that you are getting multiple replies or possibly an incorrect mac being sent in the reply it should help narrow the problem down.

Gb0mb

........99.9% User Error........

 

[ordisecours]

GOOD NEWS ???

last monday , I try something , I modify the settings of my "little" router to accept only the 3 MAC addresses necessary,

since no one is getting error with the MAJOR router.

Case seem to be solve.

Thanks to all for suggestion. long life to tek-tips forum.

..._ - _ - every trouble shooting begin with power ON !! we always forgot one day. HAVE A NICE DAY.