VLAN not working as expected - sanity check please!

RouterOS General
1

Hi,

I have been trying to get VLANs working and have partially succeded, however I have found a pretty major shortcoming and I wanted to check whether it is my fault and I completely misunderstand how VLANs are implemented or whether there is a bug in ROS.

Consider the following configuration:

/interface vlan add arp=enabled comment="" disabled=no interface=ether1 mtu=1500 name=vlan1 use-service-tag=no vlan-id=42
/ip address add address=192.168.42.254/24 broadcast=192.168.42.255 comment="" disabled=no interface=vlan1 network=192.168.42.0
/ip address add address=192.168.11.254/24 broadcast=192.168.11.255 comment="" disabled=no interface=ether1 network=192.168.11.0
/ip pool add name=dhcp_pool1 ranges=192.168.11.1-192.168.11.100
/ip dhcp-server network add address=192.168.11.0/24 comment="" dns-server=192.168.11.254 gateway=192.168.11.254
/ip dhcp-server add address-pool=dhcp_pool1 authoritative=after-2sec-delay bootp-support=static disabled=no interface=ether2 lease-time=3d name=dhcp1

This works perfectly with any device on VLAN 42… until a DHCP server is added to ether1, at which point, any device on VLAN 42 making a DHCP request is served by the DHCP server on ether1 - that is any device on VLAN 42 which issues a DHCP request is served an address in the 192.168.11.0/24 network.

So it appears that vlan1 and ether1 are bridged. Clearly this is not a good thing.

Am I being stupid?

2

I said, I said!

it happened somewhere between 3.17 and 3.19. I have opened Support Ticket#2009011266000318

every dhcp request is served both by ethernet and VLAN

they could not reproduce the issue, and there was no answers since Jan 27 =(

p.s. by the way, I’ve met the guy, that was researching this issue, on Czech MUM =) Maris, hello ))

3

Phew, it’s good it’s not my fault! I did search the forum, but I must have missed your post - sorry for that. I’ll e-mail support now.

Thanks,

4

I did not posted that on the forum =)

And you may refer to my ticket - there were some unanswered supouts ))

5

I have tried exactly the same configuration on other hardware and it works fine, so it seems to be hardware related. I am unable to reproduce on any available hardware (the PC I found the fault on has been recycled as a desktop). Strange.

6

hm… I faced that on all our routers, with different configs =) and there was no that bug in earlier versions… maybe it’s something driver-related?..