Community discussions

MikroTik App
just joined
Topic Author
Posts: 1
Joined: Wed Aug 23, 2006 7:29 pm

Feature request : DHCP Snooping with option 82

Tue Sep 26, 2006 9:32 pm

A feature invaluable to any ISP would be DHCP Snooping with option 82 as found in Cisco and AliedTelesyn products : ... 35791.html ... on%2082%22
User avatar
Alessio Garavano
Posts: 304
Joined: Sat May 29, 2004 12:49 am
Location: Corrientes, Argentina

Re: Feature request : DHCP Snooping with option 82

Mon Jul 07, 2008 7:38 am

How to implement and use this option in the MT DHCP-Server?

I think i am having some like Dynamic ARP Inspection or DHCP Snooping...

:? In the Log i can see a lot of ip assignment and deassignment from the same MAC in any seconds and all theses IPs are stay in "busy" status in the leases table.

I need to constantly check the leases table and the Log and do a rule in the bridge filter dropping the access of the MAC.

Have someone this problem?

Thanks and regards!
Alessio Garavano
just joined
Posts: 19
Joined: Thu Aug 21, 2008 3:40 pm

Re: Feature request : DHCP Snooping with option 82

Thu Aug 21, 2008 4:00 pm

I have some problem

"ip assigned", after 0,5 second - "ip deassigned" - but in DHCP-SERVER Lease status "busy"

sorry my english so bad.

Mikrotik RouterOS v.3.13, Pentum 4 1,8 Ghz, Cpu Load 48%

4 - Vlan, 1 - DHCP-Server per Vlan, Abonents over 250
User avatar
Forum Guru
Forum Guru
Posts: 8526
Joined: Mon Jun 19, 2006 11:15 pm
Location: Minsk, Belarus

Re: Feature request : DHCP Snooping with option 82

Fri Aug 22, 2008 2:26 pm

'busy' means there are already this address in the network, and it cannot be assigned second time at least until the first computer is off =)
Russian-speaking forum: Welcome!

For every complex problem, there is a solution that is simple, neat, and wrong.

MikroTik. Your life. Your routing.
just joined
Posts: 19
Joined: Thu Aug 21, 2008 3:40 pm

Re: Feature request : DHCP Snooping with option 82

Tue Aug 26, 2008 11:37 am

I know. But in this case involved only one computer. Look carefully at the time

24/08/2008 19:00:00 | dhcp info debug | server-24 assigned to 00:0E:2E:6C:00:00 -> authorized,tested,bound
24/08/2008 19:00:01 | dhcp info debug | server-24 deassigned from 00:0E:2E:6C:00:00 -> busy
24/08/2008 19:00:03 | dhcp info debug | server-24 to 00:0E:2E:6C:00:00 address alredy in use

took only three seconds
Pentium 4 1700MHz
Mikrotik RouterOS 3.13
License Level 4
Network interface 2
- on Uplink
- on with 4 vlan and 1 dhcp server per vlan

My DHCP SERVER parametrs
Name: server-24
Interface: vlan24
Lease Time: 01:00:00
Authoritative: after 2s delay
Bootp Support: Off
Add ARP For Leases: On
Always Broadcast: Off
Server-24 work with networks:
Strangely but the problem only in one range addresses 172.31.4.* (in particular addresses -,,,,, the rest are working normally), all computers in other range 172.31.5.* - work fine.

And yet. The client has two computer, one with ip - ,and with ip At first there was the problem at the second no. If you manually swap MAC-addresses or network card, problem remains, but now at the second computer. So the problem is not in the client computer.

172.31.4.* - Dead Zone?
There are thoughts?

Sorry for my English is not my native language.

Who is online

Users browsing this forum: Baidu [Spider], OlofL and 176 guests