my dhcp server (MT) deassign and assign ip to clients (one at a time) every 10 minutes aprox…
when the dhcp server deassign and assign an ip, there is about 10-15 seconds of network interruption… and that’s annoyance…
why this happens…?
here is a capture of the log
dhcp deassigned
dhcp1 assigned?
Seems to me you’re running two DHCP Servers…
Thank you for answering..
I have only 1 dhcp server configured, look
i think it’s correct to deassign and assign an ip to a host when the lease expires, but not every 5-10 minutes
I don’t get a deassigned message when my lease expires, as the client renews the lease, not request a new lease…
I would enable the always broadcast option though. Some clients does have issues with DHCP when the reply is not received via a broadcast message…
i thought it was correct to deassign and assign when a lease expires…
so there is a problem…
everything was fine for 5 month since a few days ago. now when my router’s address is deassigned and assigned, i lose connection (every 5-10minutes) messenger closes, winbox disconnects, etc.
i tried with another router and i have the same problem
Does the IP address change when the DHCP client renews?
If the IP Changes, then it releases the lease and request a new one (which causes the IP to be dropped on the client, all connections are then closed, and the system requests a new IP)…
Perhaps post the entire DHCP config, let’s see what is going on… /ip dhcp-server export I believe if memory servs me right…
I had the same problem.
I when to the clients site and noticed the client had a home router.
It was connected and configured correctly and it would never accept an IP address.
I had the client replace the router and everything is now OK.
Hmm sorry, didn’t think about the log you posted…
The IP doesn’t change, the DHCP Server does broadcast… What client is this where the issue is?
The only thing I can recommend, is that the Client is haywire. The client essentially is not receiving the reply from the DHCP Server, falls back to the config it had originally (before the lease expired), and requests a new one. This goes on untill the client eventually receives a message it accepts.
Can you check whether the broadcast reply (ACK) actually arrives at the client? Packet dump on the client will be your only choice here… either the broadcast is being dropped / going missing on the wire somewhere, or the client bluntly just does not accept it (which I can’t think will be the case, as you said it did work previously).
# jan/19/2007 09:26:15 by RouterOS 2.9.38
# software id = *********
#
/ ip dhcp-server
add name="dhcp1" interface=LANbridge lease-time=3d address-pool=static-only always-broadcast=yes \
authoritative=after-2sec-delay disabled=no
/ ip dhcp-server config
set store-leases-disk=5m
/ ip dhcp-server lease
add address=172.16.0.27 mac-address=00:06:4F:37:A0:D0 comment="PC1" disabled=no
add address=172.16.0.30 mac-address=00:0F:3D:3B:EF:B9 comment="PC2" disabled=no
add address=172.16.0.33 mac-address=00:04:E2:9B:8F:42 comment="PC3" disabled=no
add address=172.16.0.34 mac-address=00:11:95:20:FB:8C comment="PC4" disabled=no
add address=172.16.0.35 mac-address=00:11:95:4C:EC:8A comment="PC5" disabled=no
...
and several more leasses
...
/ ip dhcp-server network
add address=172.16.0.0/21 gateway=172.16.0.1 dns-server=172.16.0.1 \
comment="added by setup"
i replace the router and the problem persists…
as you can see in the log, this problem is affectig not only one client.
wireless clients are less often affected then me. I’m a wired client.
Just as a test (I realise this is not a solution)…
Can you open the firewall so that no packets are dropped. You’ll have to do this on a MAC and IP Layer… (so it will be a allow any from any via interface). Also considering it seems like a bridged interface, I’ll also look for things possibly being dropped on the bridges…
Perhaps something is dropping the broadcasts (or related) packets coming in / going out of the router… Looking at the debug log you pasted, it looks allot to me like the clients is not receiving the ACK Broadcast from the DHCP Server…
you say disable firewall in the router (client side) or in mikrotik router?
I’d do both as a start…
If something is dropping the packets, you’d need to debug to find out what /where it is being droped…
i disabled all mikrotik’s firewall rules… and … 
everything is ok in the last hour 
i will monitor the connection a couple of hours and then i will turn on rules one by one and see which one is disturbing…
Thank you savage for your help… and then i will post the annoyance firewall rule.
Al ready found a sollution ?
Ive got the same problem. But when i disable all firewall rules the problem is still there. The problem is related to the LAN interface. But when i make a VPN Connection the problem isnt there.
Proxy-ARP is enabled on the lan interface
Disabled Proxy-ARP and working DHCP
Enabled Proxy-ARP still working DHCP
Reboot for check
Problem is there again. For now disabled Proxy-ARP and everything seems fine
i don’t use vpn
i have proxy-arp disabled
i don’t know exactly what my problem was, but i think it was because of a wrong p2p packet mark and drop. i have all p2p manipulation rules disabled and the problem disappeared. I will work to fix my p2p rules another day.