DHCP Discover over Bridged radios

salemmahara · Mon Aug 13, 2018 11:09 am

Hello there
We have a setup like this:

Client------switch-------BridgeMikrotikRadio1<----------->BridgeMikrotikRadio2--------DHCPServer(Switch)

But when client discover DHCP can't find it! We tried to check it with an ACL on switch to determine if discovery packet are received or not. We found switch doesn't receive any discovery packet !

We have similar configuration with copper between another switch and DHCP Server Switch and it's working just fine. So its configuration looks okay and working.
I think there is a problem with radios in path which don't pass discovery packets! I checked their configuration, no DHCP server , client and relay is configured there .

Any idea or similar problem there?

salemmahara · Mon Aug 13, 2018 7:01 pm

Is there anyone who wants to help!?

sindy · Mon Aug 13, 2018 10:04 pm

You haven't shown the configurations (see my automatic signature), but have you checked this manual page? The point is that if you haven't chosen the correct bridge mode, all the DHCP packets from the client arrive to the server with the MAC address of the station.

salemmahara · Tue Aug 14, 2018 6:53 pm

You haven't shown the configurations (see my automatic signature), but have you checked this manual page? The point is that if you haven't chosen the correct bridge mode, all the DHCP packets from the client arrive to the server with the MAC address of the station.

Hello Sindy
Thanks for replying.

Configuration is AP & SU .
AP has 4 interface (ether,wlan,bridge,wds)
SU has 3 interface (ether,wlan,bridge)
There is a Switch (dhcp server) behind AP radio. Client is connected to SU.

When we capture ingress traffic on switch connected to AP, it doesn’t show any Dhcp descovery pcket! It means radios are not passing this pcket across each other.

Radios are QRT

sindy · Tue Aug 14, 2018 8:48 pm

Configuration is AP & SU .

Configuration is the complete output of /export hide-sensitive, anonymized if necessary, see my signature for details. The verbal description does not provide enough information.

salemmahara · Wed Aug 15, 2018 6:33 am

Configuration is AP & SU .
Configuration is the complete output of /export hide-sensitive, anonymized if necessary, see my signature for details. The verbal description does not provide enough information.

AP:

/interface bridge
add name=bridge1
/interface wireless
set [ find default-name=wlan1 ] band=2ghz-onlyn channel-width=20/40mhz-Ce \
    default-authentication=wxyz default-forwarding=no disabled=no frequency=2707 \
    frequency-mode=superchannel mode=bridge radio-name=\
    "ap" scan-list=2702,2707,2712 ssid=wxyz \
    wds-default-bridge=bridge1 wds-mode=dynamic wireless-protocol=nv2
/interface wireless nstreme
set wlan1 enable-nstreme=yes framer-policy=best-fit
/interface wireless security-profiles
set [ find default=yes ] supplicant-identity=MikroTik
/tool user-manager customer
set admin access=\
    own-routers,own-users,own-profiles,own-limits,config-payment-gw
/interface bridge port
add bridge=bridge1 interface=ether1
add bridge=bridge1 interface=wlan1
/interface wireless access-list
add interface=wlan1 mac-address=wxyz vlan-mode=no-tag
/ip address
add address=1.1.1.1/24 interface=bridge1 network=1.1.1.0
/ip route
add distance=1 gateway=1.1.1.10
/system identity
set name="AP"
/system lcd
set contrast=0 enabled=no port=parallel type=24x4
/system lcd page
set time disabled=yes display-time=5s
set resources disabled=yes display-time=5s
set uptime disabled=yes display-time=5s
set packets disabled=yes display-time=5s
set bits disabled=yes display-time=5s
set version disabled=yes display-time=5s
set identity disabled=yes display-time=5s
set bridge1 disabled=yes display-time=5s
set wlan1 disabled=yes display-time=5s
set ether1 disabled=yes display-time=5s
set wds1 disabled=yes display-time=5s
/tool user-manager database
set db-path=user-manager

SU:

/interface bridge
add name=bridge1
/interface wireless
set [ find default-name=wlan1 ] adaptive-noise-immunity=client-mode band=\
    2ghz-onlyn channel-width=20/40mhz-Ce disabled=no frequency=2702 \
    frequency-mode=superchannel mode=station-wds radio-name=\
    "su" scan-list=2702,2707,2712 ssid=wxyz \
    wds-default-bridge=bridge1 wds-mode=dynamic
/interface wireless nstreme
set wlan1 enable-nstreme=yes
/interface wireless security-profiles
set [ find default=yes ] supplicant-identity=MikroTik
/tool user-manager customer
set admin access=\
    own-routers,own-users,own-profiles,own-limits,config-payment-gw
/interface bridge port
add bridge=bridge1 interface=wlan1
add bridge=bridge1 interface=ether1
/ip address
add address=1.1.1.2/24 interface=bridge1 network=1.1.1.0
/ip route
add distance=1 gateway=1.1.1.10
/system identity
set name="SU"
/system lcd
set contrast=0 enabled=no port=parallel type=24x4
/system lcd page
set time disabled=yes display-time=5s
set resources disabled=yes display-time=5s
set uptime disabled=yes display-time=5s
set packets disabled=yes display-time=5s
set bits disabled=yes display-time=5s
set version disabled=yes display-time=5s
set identity disabled=yes display-time=5s
set bridge1 disabled=yes display-time=5s
set wlan1 disabled=yes display-time=5s
set ether1 disabled=yes display-time=5s
/tool user-manager database
set db-path=user-manager

I attached a simple drawing of scenario.
Note:
all devices are in VLAN1. If we can solve the problem, then we go for VLANs and DHCP server should assign IPs across vlans . SO the links which are connected to both switches are in Trunk mode. Radios must pass traffic for any kind of vlans. They should also work exaccccccccccctly like a fiber or copper media. withouuuuuuuuuut any data manipulation! ( L2 and L3 information like intervlan routing and intravlan switching) . They should also answer their management traffic.

sindy · Wed Aug 15, 2018 2:31 pm

OK. I have replicated your wireless configuration (on a pair of 6.43rc12 which happened to be handy) and it works properly - the DHCPDISCOVER packets from a DHCP client at STA side are visible on the bridge at AP side.

Can you please post /interface bridge port print from the AP side while the wireless link is up?
There should be an item like
6 D wds1 bridge1

Use of station-wds mode causes the AP to dynamically create an individual interface for each connected station and dynamically make it a member port of the bridge indicated in wds-default-bridge of the wireless configuration, and it seems it takes some seconds after the wireless link goes up before these dynamic items appear.

If the item is there, run /tool torch bridge1 src-address=0.0.0.0/0 dst-address=0.0.0.0/0 ip-protocol=any port=any at both AP and STA to check whether the DHCP discovery arrrives to the STA bridge and whether it reaches the other end of the wireless link at least internally. Forget about the src and dst addresses, they are assigned in a confusing way.

Other than that (and too early for that probably), for wireless transmission of a VLAN trunk, I would use station-bridge mode rather than station-wds as in this case there is only one interface common for all bridge-mode STAs, and I would follow this instruction on setting up the VLANs.

DHCP Discover over Bridged radios

DHCP Discover over Bridged radios

Re: DHCP Discover over Bridged radios

Re: DHCP Discover over Bridged radios

Re: DHCP Discover over Bridged radios

Re: DHCP Discover over Bridged radios

Re: DHCP Discover over Bridged radios

Re: DHCP Discover over Bridged radios

Who is online