Ahh. Thank you. Now I have got the plug visible on the network and giving addresses in the correct subnet.
The only unusual thing is this message repeated many times in syslog
[125193.455174] br0: port 1(uap0) entering forwarding state
[125193.460527] br0: port 1(uap0) entering forwarding state
[125208.484424] br0: port 1(uap0) entering forwarding state
[125229.386907] br0: port 1(uap0) entering forwarding state
[170338.708237] br0: port 1(uap0) entering forwarding state
[170338.713591] br0: port 1(uap0) entering forwarding state
[170353.724426] br0: port 1(uap0) entering forwarding state
[171183.794291] br0: port 1(uap0) entering forwarding state
I searched the web and there are many different causes of this error but nothing seemed relevant to my circumstances.
Here is the latest version of /etc/network/interfaces
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).
# The loopback network interface
auto lo br0
iface lo inet loopback
# The primary network interface
iface eth0 inet manual
#The wireless interface
iface uap0 inet manual
pre-up modprobe uap8xxx
post-up /etc/network/guruplug-wl-conf.sh start
post-down /etc/network/guruplug-wl-conf.sh stop
# address 0.0.0.0
iface br0 inet static
bridge_ports uap0 eth0
#For some reason, uap0 does not end up in the bridge.
up /sbin/brctl addif br0 uap0
Here are the relevant sections of /etc/dnsmasq.conf
# If you want dnsmasq to listen for DHCP and DNS requests only on
# specified interfaces (and the loopback) give the name of the
# interface (eg eth0) here.
# Repeat the line for more than one interface.
# On systems which support it, dnsmasq binds the wildcard address,
# even when it is listening on only some interfaces. It then discards
# requests that it shouldn't reply to. This has the advantage of
# working even when interfaces come and go and change address. If you
# want dnsmasq to really bind only the interfaces it is listening on,
# uncomment this option. About the only time you may need this is when
# running another nameserver on the same machine.
I don't know much about the workings of networking: is the bind interfaces br0
causing the problem?
Here are the uncommented sections of /etc/dhcp/dhclient.conf which is what gets
an ipaddress for the plug
send host-name = gethostname();
request subnet-mask, broadcast-address, time-offset, routers,
domain-name, domain-name-servers, domain-search, host-name,
netbios-name-servers, netbios-scope, interface-mtu,