[Dnsmasq-discuss] DHCP failure when changing SSID on same network

Chris Green cl at isbd.net
Mon May 14 18:50:57 BST 2018


I have a large house and run two Draytek Vigor routers to provide full
coverage. The 'main' router is a Draytek 2860n which has the VDSL
connection to the internet. The second router is a Draytek Vigoer
2820n which has no WAN connections and just has its LAN connected to
the 2860n's LAN side.

DHCP/DNS is provided by a Raspberry Pi running dnsmasq.  Everything is
otherwise pretty standard, 192.168.1.x private network with the 2860n
at 192.168.1.1 and the Pi at 192.168.1.2.

I have the routers' WiFi set up so they have different SSIDs. In
general it all works fine, I can connect my laptop to either SSID as
required.

The problem I have is when I move around the house. My laptop runs
xubuntu 17.10 and uses Network Manager to handle the networking. So,
say I'm connected to 2820n and move to the other side of the house
where I need to connect to 2860n. I manually use the Network Manager
applet to disconnect from 2820n and connect to 2860n. It appears to
work fine and says I'm connected but most times that I do this the
DHCP set-up fails. I have a connection but there is no default route
and no DNS and the laptop has no IP address assigned (all IPV4 this).
Sometimes it works OK and usually if I disconnect and wait a while
(say a minute or two) and then reconnect it will work OK.

It seems as if dhclient is failing as if I run it manually when in the
not working state it just hangs.  Does dnsmasq have some sort of delay
before 'dropping' a DHCP client?  I.e. is it possible that dnsmasq
sees the same MAC address re-connecting and assumes that it still has
its IP setup?  If so is there some way I can make dnsmasq quicker at
seeing that a client has disconnected?

-- 
Chris Green



More information about the Dnsmasq-discuss mailing list