Wifi DHCP Forwarding/Relay

Installing and Using OpenWrt Network and Wireless Configuration
1

Hi @ All, :smiley:

I try to forward the Wifi DHCP (VLAN 200) traffic to my internal DHCP Server (VLAN 10).

VLAN 5 (192.168.1.0/24) = Transfer network between CORE Switch and my Router

router = 192.168.1.1 / Core = 192.168.1.2

VLAN 10 (10.10.10.0/24) = Server LAN (Here is my DHCP 10.10.10.20)

core = 10.10.10.1 / router = ???

VLAN 100 (10.10.100.0/24) = Internal LAN (wired)

Only for complete informations

VLAN 200 (10.10.200.0/24) = Wifi (Internal Wifi Clients)

router = ??? / core = 10.10.200.2

My System:
Hostname LEDE
Model Linksys WRT1900ACS
Firmware Version LEDE Reboot 17.01.4 r3560-79f57e422d / LuCI lede-17.01 branch (git-17.290.79498-d3f0685)

I thought I can solve my DHCP issue by myself because i can configure differents devices from Cisco, Dell Sonicwalls and so on... but with this here i dont know what to do to solve my issue.

So my question is how must i cofigure the ACS1900 to forward all DHCP traffic to my DHCP Server in VLAN 10.

Internal in my LAN DHCP related stuff works fine the only thing that did not work is my Wifi.

I hope someone can help me.

Greetingd Ronny :slight_smile:

2

DHCP is link-local broadcast so it isn't forwarded at Level 3. If you want to maintain network separation, you'll need a DHCP relay on each VLAN/subnet and a DHCP server configuration that is aware of how to assign the various DHCP pools based on the originating network. I doubt dnsmasq can handle that. You might want to look to see if kea has been ported to LEDE, or run it on other hardware.

If you're running Cisco switches, they often have a built-in DHCP relay that can be configured.

3

Hi,

yes my cisco switches are configured to relay the DHCP Requets. That works well on all my networks. But I don't know how to configure the ACS1900 (192.168.1.1) to forward these requests to my core switch (192.168.1.2) On my Cisco Core switch I have configured an ip dhcp relay for each network. And the DHCP Server (10.10.10.20) is configured so serve IP Adresses for all needed ranges.

still the question is how to configure the ACS1900.

Greetings

4

'dnsmasq' likely isn't going to handle it. I'd either run kea on another box, or see if you can get it to compile for LEDE/OpenWRT.

http://kea.isc.org/docs/kea-guide.html#dhcp4-subnet-selection

A simpler option would be to run a DHCP server on each of the VLANs since you don't have any overlap in IPv4 address space

5

dnsmasq supports dhcp relay, but LuCI does not support setting it

the configuration file must be edited manually
/etc/config/dhcp

example:

config relay 'lan'
        option interface 'lan'
        option local_addr '192.168.1.1'
        option server_addr '192.168.4.1'
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