Network not stable, intermittent ping/uptime on servers PC's and Printers

Hi All,

I take care of the PC's/Network for a hotel and have come into a problem i cant quite get my head around,

This morning at about 7 o'clock i received calls saying internet was down, no printers are working, some PC's have no network/drive access etc, I've looked into it and have found the following:

All printers are connected power wise and to the network, I can ping 1-2 of them however the others the first ping replys then the rest dont (even using -t switch) If i leave it for 5 minutes then ping again i get the same thing, one reply then nothing.

When pinging servers/PC's the majority will ping all 4 back no problem but some ping in the following way:
1st replies
2nd timeout
3rd replies
4th replies
following this, if you ping again all 4 will reply, however leave for 5 minutes and ping again and you get the same issue

Some ping in the same manner as the printers where the first will reply and then none after that.

All pings that do reply are =1ms or there about.

There are fiber connections between parts of the hotel and i've known fiber previously to either work fine or fail completely so I have ruled this out for the moment.

I've seen this issue before in other networks and usually points to a small switch being used on the network somewhere causing the issue however I have covered the whole site unplugging any small switch one by one and testing stability without any answers.

Windows Firewall is off network wide, have also tested by turning off all of our AV/Firewall software without any luck.

I have replaced major switches one by one, monitored and same issues occur.

I have replaced a series of network cables throughout the hotel also

to add - Domain Controller is Server 2003 Enterprise - and currently will not show up windows explorer just a blank screen however when RDP'd into everything is fine all services running etc

Please ask for anymore information about the issue, I have looked at it from pretty much every angle so should be able to answer any questions.

Any help would be greatly appreciated,

Cheers,
Pete
pd_Asked:
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hdmillerCommented:
You try pinging the loopback on the DC?  Maybe NIC failing.
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TimotiStDatacenter TechnicianCommented:
First guesses:

- rogue DHCP server on network,
- failing NIC with ARP issues,
- rogue Netbios subnet master browser (should mess up everything referred by name, but work fine with IP addresses),
- user PC running some worm or something.

If you have decent switches, you could implement: DHCP snooping, ARP protection, source IP protection, broadcast/multicast storm control.

Tamas
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pd_Author Commented:
Hi There,

Turned out a member of staff had patched the guest network into our office network at some point which like you said meant there was two DHCP servers on the same network conflicting,

Cheers for the help,

Pete
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