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jacob_pro DD-WRT Novice Joined: 25 Sep 2016 Posts: 7
Posted: Sun Sep 25, 2016 15:48 Post subject: DHCP Forwarding Relay IP Helper with DNSMasq / DHCPd / FWD
Hi, I know a lot of networking, but I am completely new to DD-WRT and linux!
I need some help setting up DHCP Forwarding. I would like to configure a DHCP relay on a per-VLAN basis (much like the Cisco ip helper-address command used per interface).
I can see there are 3 different DHCP packages I can use:
DHCPd
DNSMasq
DHCP Forwarder (dhcp-fwd)
I have not been able to get the DHCP forwarder mode to work, and neither is there any to manually configure it in the web GUI. I can see the configuration file for it when using SCP but I do not know how it should be configured or how to save configurations to the memory?
I may be wrong but I don't think it is possible for DHCPd to relay?
I know that DNSMasq can relay (--dhcp-relay=...) according to its own documentation (http://www.thekelleys.org.uk/dnsmasq/docs/dnsmasq-man.html) I can see how to add commands in the services tab but these are in a different format to those used in the DNSMasq documentation, is there any way to use the --dhcp-relay in DD-WRT?
(I am using an ASUS-RT-N66U, build 26138M big)
Thanks in advance
Jacob
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Per Yngve Berg DD-WRT Guru Joined: 13 Aug 2013 Posts: 6856 Location: Romerike, Norway
Posted: Sun Sep 25, 2016 16:23 Post subject:
Setup->Basic Setup->Network Address Server Settings (DHCP)->DHCP Type
You can select between DHCP Server or DHCP Forwarder.
When set to Forwarder, you enter the ip address of the DHCP server that serve the sub-net.
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jacob_pro DD-WRT Novice Joined: 25 Sep 2016 Posts: 7
Posted: Sun Sep 25, 2016 16:26 Post subject:
Thanks for your reply.
I understand that I can choose a DHCP forwarder but I cannot configure which interfaces it runs on.
I need it to forward requests on VLAN13 to an IP address (dhcp server) on VLAN10.
I can see there is a config file (dhcp-fwd) on the router when I browse SCP but I don't know how to edit it or save it permanently.
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jacob_pro DD-WRT Novice Joined: 25 Sep 2016 Posts: 7
Posted: Sun Sep 25, 2016 17:12 Post subject:
I can see the dhcp-fwd config in /tmp (see photo)
But I do not know how to permanently edit it for the other VLANs.
As for the br0 which is in the dhcp-fwd config already I can get it to relay to the DHCP server (source 68 to port 67) but it will not receive the DHCP offer (source 67 to port 67) (see photo).
Description:
will not receive on port 67
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Description:
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Per Yngve Berg DD-WRT Guru Joined: 13 Aug 2013 Posts: 6856 Location: Romerike, Norway
Posted: Sun Sep 25, 2016 18:04 Post subject:
That file does not survive a reboot.
Add a USB Memory Stick and load a JFFS volume to host the file.
Reload the service with a config file on the jffs volume.
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jacob_pro DD-WRT Novice Joined: 25 Sep 2016 Posts: 7
Posted: Sun Sep 25, 2016 18:09 Post subject:
Thanks that is useful to know.
What I would really like to know is how to use the DNSMasq
configuration commands here:
http://www.thekelleys.org.uk/dnsmasq/docs/dnsmasq-man.html
Clearly they are very different from what is used in DD-WRT, (http://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=blob_plain;f=dnsmasq.conf.example)
Basically I need to use the relay command
--dhcp-relay=<local address>,<server address>[,<interface]
Thanks
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jacob_pro DD-WRT Novice Joined: 25 Sep 2016 Posts: 7
Posted: Sun Sep 25, 2016 18:17 Post subject:
I have been trying to run the commands for dnsmasq in the console, but most don't seem to do anything except --test.
Description:
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Per Yngve Berg DD-WRT Guru Joined: 13 Aug 2013 Posts: 6856 Location: Romerike, Norway
Posted: Sun Sep 25, 2016 18:29 Post subject:
Paste into the "Additional DNSMasq Options" in the Services Tab
dhcp-relay=10.13.1.1,192.168.1.8,vlan13
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jacob_pro DD-WRT Novice Joined: 25 Sep 2016 Posts: 7
Posted: Sun Sep 25, 2016 18:50 Post subject:
Thanks for your reply.
I have already tried that but it doesn't seem to do anything.
When I read the dd-wrt commands here it doesn't mention anything about dhcp-relay
https://github.com/mirror/dd-wrt/blob/master/src/router/dnsmasq/dnsmasq.conf.example
They are all in a completely different format to the standard DNSMasq configuration guide.
I even tried using:
interface=vlan13
dhcp-relay=10.13.1.1,192.168.1.8,vlan13
dhcp-relay=vlan13,10.13.1.1,192.168.1.8
The OpenWRT version explains how they use 2 config files - https://wiki.openwrt.org/doc/howto/dhcp.dnsmasq
I wonder if i put the --dhcp-relay command in a text file etc/dnsmasq.conf it would work. but I do not know how to restart the service
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Per Yngve Berg DD-WRT Guru Joined: 13 Aug 2013 Posts: 6856 Location: Romerike, Norway
Posted: Sun Sep 25, 2016 19:03 Post subject:
killall -9 dnsmasq;
sleep 3;
dnsmasq -xxx
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jacob_pro DD-WRT Novice Joined: 25 Sep 2016 Posts: 7
Posted: Sun Sep 25, 2016 19:15 Post subject:
I can't actually create the file in etc/dnsmasq.conf because it is read only
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egc DD-WRT Guru Joined: 18 Mar 2014 Posts: 12834 Location: Netherlands
Posted: Mon Sep 26, 2016 12:23 Post subject:
jacob_pro wrote: I can't actually create the file in etc/dnsmasq.conf because it is read only
change it with the chmod command, something like
"chmod 777 myfile" I think
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