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Linux access point (airmon-ng/airmon-ng) not working

Background: I am trying to set up an access point on Linux. The ultimate aim is to run SSLStrip (for an exercise) so I need to be able to do something like this, to redirect port 80 traffic through port 10000, on which SSLStrip listens.

iptables -t nat -A PREROUTING -p tcp --destination-port 80 -j REDIRECT --to-port 10000

Using Linux - Kali2, 64bit. Machine has internet access via eth0.

This is how I am setting up the access point:

airmon-ng start wlan0 6
modprobe tun

ifconfig wlan0mon down
iwconfig wlan0mon mode monitor
ifconfig wlan0mon up

airbase-ng -e "MyAccessPoint" -c 6 wlan0mon &

ifconfig "at0" up
ifconfig "at0" "" netmask ""
ifconfig "at0" mtu 1500
route add -net "" netmask "" gw "" dev "at0"

Into /etc/dhcp/dhcpd.conf I put the following:

subnet netmask {
    default-lease-time 3600;
    max-lease-time 7200;
    option subnet-mask;
    option broadcast-address;
    option routers;
    option domain-name-servers;
    option domain-name “freeinternet.co.uk” 

Check that /etc/default/isc-dhcp-server has INTERFACES=”at0”

Start the DHCP Server:

/etc/init.d/isc-dhcp-server restart

Configure NAT and enable ip forwarding:

iptables --flush
iptables --table nat --flush
iptables --delete-chain
iptables --table nat --delete-chain
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
echo "1" > /proc/sys/net/ipv4/ip_forward

At this stage I believe I should be able to connect a client to my access point and browse the web.

The client sees the access point, connects, gets an IP address from the server's DHCP ( and then has the following routing table:

mark@laptop15:~/TT$ route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface         UG    0      0        0 wlan0   U     9      0        0 wlan0

However it cannot even ping the server ( - no errors, we just don't get the pings back:

mark@laptop15:~/TT$ ping
PING ( 56(84) bytes of data.

And it stays like that forever.

What am I doing wrong please?