Problem with dnsmasq that I can't find a solution for

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RubenatorX
DD-WRT Novice


Joined: 29 Oct 2013
Posts: 1

PostPosted: Tue Oct 29, 2013 18:21    Post subject: Problem with dnsmasq that I can't find a solution for Reply with quote
Okay so, I currently have a very simple network. A linksys e1500 with dd-wrt on it, with some devices hooked up to it, including another wireless router functioning as an AP.

As long as I don't use dnsmasq, everything functions hunky-dory. But I would like to have local hostname resolution. From what I have read, the best way to do this means using dnsmasq for both dhcp and dns.

THE PROBLEM:
Whenever I turn dnsmasq on for dhcp and dns my computer can no longer obtain an ip address from the router, and no longer has access to the internet (Comcast).

SETTINGS DETAILS:

Setup > Router IP->
Local IP Address: 192.168.1.1
Subnet Mask: 255.255.255.0
Gateway: 0.0.0.0
Local DNS: 0.0.0.0

Setup > Network Address Server Settings (DHCP)->
DHCP Type: DHCP Server
DHCP Server: Enabled
Start IP Address: 192.168.1.155
Maximum DHCP Users: 100
Static DNS 1: 192.168.1.1
Static DNS 2: 208.67.220.222 (opendns)
Static DNS 3: 208.67.220.220 (opendns)
WINS: 0.0.0.0
Use DNSMasq for DHCP: Enabled
Use DNSMasq for DNS: Enabled
DHCP-Authoritative: Tried both

Services > DHCP Server->
Use JFFS2 for client lease DB:(Not mounted)
Use NVRAM for client lease DB: Disabled
Used Domain: LAN & WLAN
LAN Domain: lan
Additional DHCPd Options: none

Services > DNSMasq->
DNSMasq: Enabled
Local DNS: Tried both
No DNS Rebind: Enabled
Additional DNSMasq Options:
I've tried a few things here, but its my understanding that I should probably have "strict-order" and possibly "local=/lan/"

I also have many reserved static IPs for addresses under 192.168.1.156, including one for my PC, specifically 192.168.1.13

Hardware: Linksys E1500
Firmware: DD-WRT v24-sp2 (03/25/13) big


SCENARIO:
1) everything works
2) I save the settings as seen above
3) I do "ipconfig /release" and "ipconfig /renew", but the renew fails complaining about not being able to access a file for a loopback interface
4) I lose all network connectivity
5) I set my PC's IPv4 statically to 192.168.1.13
6) I now can reach the router, but not the internet
7) I then put the configuration back to the way it was when it worked, reset my IPv4 to dynamic, do a /release/renew, and I have internet again.

WHAT AM I DOING WRONG???

Random observation:
When all is working my ipconfig /all has a Connection-specific DNS Suffix ending in ".comcast.net." rather than "lan". Dunno if its important.
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Max Hopper
DD-WRT Novice


Joined: 28 Jun 2013
Posts: 11

PostPosted: Mon Apr 14, 2014 14:02    Post subject: Who moved my cable? Reply with quote
Indeed, dnsmasq 'solves' the problem of how to resolve local hostnames and DHCP leases all in one go.

N.B. many WAN modem/router devices do not offer a DNS service. DHCP clients are displayed in the web GUI of the WAN modem. This is not a local DNS

In which router Ethernet port is the cable to the WAN modem? A LAN and not the WAN port?

Without modification to the OOTB dd-wrt setting Setup | Basic Setup | WAN Setup | WAN Connection Type |
Connection Type <Automatic Configuration - DHCP>
NAT is active only on the router WAN port. And when the LAN side address of the WAN modem is not in the subnet selected by Setup | Basic Setup | Network Setup | Router IP | Local IP Address <192.168.1.0/24> IP packets from the LAN side of the WAN modem have no path to the router.

To overcome the subnet mismatch:
    alter the LAN address of the WAN modem <192.168.1.(2-154)>
    disable the DHCP server of the WAN modem lest there be two DHCP servers randomly handling DHCP DISCOVER requests
    -- or --
    move the WAN modem <-> router cable to the router WAN port

N.B. moving the WAN modem <-> router cable to the router WAN port effects 'double NATting' (unnecessary overhead)
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