Router interface unreachable!

By nizeyimana_peter ·
I have a net of around 40 users connected thru' 4 switches to a cisco 2600 router which is gateway. I have a seperate DHCP server running on windows 2003 server. Since recently the net works fine for 3 hours and computers are no more able to ping the router interface. But they ping each other and the DHCP server as well. I then have to reload the router and repair the DHCP server NIC and the net works fine again for 3 or 4 hours!
Any help..!?

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I would supsect the router is defective??

by 1bn0 In reply to Router interface unreacha ...

When you refer to the "the net" is that hte local area network or the internet is not accessable.

If you power up a workstation after your 4 hour timeout, does it get an IP address and can it ping other workstations. If so the DHCP is fine. You need to narrow down the problem to one or the other.

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What is the status of the interface?

by NetMan1958 In reply to Router interface unreacha ...

Have you tried running "show interface" on the affected interface when it happens? For instance if it is interface fa0/1, run the command:
router#show interface fa0/1

Try that and post the output if you need to.

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Have tried running show interface?By net u mean LAN or Internet?

by nizeyimana_peter In reply to What is the status of the ...

Thank you guys for ur responses but i have checked the status of the interfaces, they are up...and about the network...i am connected to internet through the router and when the problem comes i cant ping the interface of the router meaning i cant access the internet but the LAN still works fine!

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by NetMan1958 In reply to Have tried running show i ...

You said that when the problem occurs you reload the router and repair the DHCP server NIC. Could you elaborate on what you are doing when you "repair the DHCP server NIC"?

What happens if you just reload the router without repairing the DHCP server NIC?

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DHCP server NIC!

by nizeyimana_peter In reply to Question

To repair the NIC i just right click the icon in the task bar and do repair...!
But per now the problem has worsened, the LAN goes down and no machine can ping its peers neither the router interface. I reload the router, repair the DHCP card and restart the switches to make it work again ...and for the last four days i had to do it twice! I suspect viruses as some of the machines have got their date and time changed back to 2005.
But i am running a corporate version of Kaspersky v6 and it was well installed before the problems started!
I would appreciate if u could help me out!

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The next time it happens

by NetMan1958 In reply to DHCP server NIC!

Go to 2 different workstations and try to ping each one from the other. If they can't ping each other, then on each workstation - open a command prompt and run "ipconfig /all" (without the quotes). This will show you the ip address and MAC address. Make sure each machine has an appropriate ip address and if it does, write down the MAC address for each machine.
Then on each machine run "arp -a" (without quotes). Look at the output and make sure the arp table displays the correct MAC address for the ip address of the other machine. Post the results if would like and I'll take a look.

Assuming all the above looks OK, I would reboot 1 machine and install Wireshark on it. Then run Wireshark and see if you have a broadcast storm or some other anomaly occuring.

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