IP Problems !!

RouterOS General
1

Hello All,

i have strange problem, first thing i have a rb1100ahx (today i upgrade to latest version and firmware), and i have around 40 PC working in my network,
every thing was working fine until three days ago, i have 4 PCs suddenly not accessing the internet.
when i change the IP from DHCP to static the can access the internet and after a while same problem happen,
and i have to change from static to DHCP !!!
and this problem happening only in these 4 PCs !!

what is wrong I need help Please.

2

What version have you started upgrade from? Read the changelog … there was a lot of changes. How are they connected (these 4 PCs) to Mikrotik? Directly? Via a switch?

3

Hello Dear,

i upgrade from 6.27 to 6.40.3, but the problem was there before and after the upgrade.
they are connected through switch not directly.

4

Do you have more PCs “behind” this switch or are these 4 PCs only connected to it? Could you move them to different ports in the switch or move them to other working part of the net to eliminate problems of the switch?

EDIT:

Do you have address pool big enough to serve all PCs?

5

Hello Dear,


yes there are another PCs on the same switch, ok i’ll change the port of the PCs with problem.
and yes my dhcp pool is big enough

6

dear, the problem is happening everyday at 06:00 PM
nothing happened when i changed ports

7

Try to monitor the PC connected directly to Tik without switch. If this fine, means switch is corrupted.

8

Most likely there is a rogue DHCP server on your network, e.g. someone has plugged in a home router to use as an access point.
You can go to the Alerts tab in the DHCP server config and configure an Alert for this condition.
At least you can see in the log if it occurs and you can configure a script to e.g. send a mail message.

9

As said, there may be a rogue DHCP server. Other possibility is an IP conflict. We had another user complaining here, and the symptoms looked like yours. At the end he had a “ghost” printer on the network, with static IP - and no one knew it.