The following scriptlet allows to add a MAC address of a wireless device to the access allow list of a Medion MD 90400 Wireless Lan Set (A DSL router and wireless LAN switch sold in Germany) bypassing the stupid javascript checks of the input data. (In my case, the native web interface didn't allow a MAC address to start with an odd number)

password=<router password>
mac=<mac to add>
router=<router ip or dns name>
wget --http-user bla \
--http-password "${password}" \
--post-data 'i1_3_6_1_4_1_937_3_1_3_2_2_1_4_*=5&m1_3_6_1_4_1_937_3_1_3_2_2_1_2_*='"${mac}"'&i1_3_6_1_4_1_937_3_1_3_2_2_1_3_*=1&i1_3_6_1_4_1_937_3_1_3_2_2_1_4_*=1' \
'http://'"${router}"'/cgi-bin/setobject?/lib/popup/close_window.shtml'

Same problem arises when setting a dedicated constant IP number to a device. Same solution applies:

password=<router password>
ip=<ip number to reserve>
mac=<respective mac>
router=<router ip or dns name>
wget --http-user bla \
     --http-password "${password}" \
     --post-data 'i1_3_6_1_4_1_937_2_1_11_2_12_1_99_*=5&setobject_macAddress=m1_3_6_1_4_1_937_2_1_11_2_12_1_3_*='"${mac}"'&setobject_ipAddress=a1_3_6_1_4_1_937_2_1_11_2_12_1_2_*='"${ip}"'&i1_3_6_1_4_1_937_2_1_11_2_12_1_99_*=1' \
     'http://'"${router}"'/cgi-bin/setobject?/lib/popup/close_window.shtml'

This scriptlet allows you to get your public IP when using a MD 90400 Wireless Lan Set for DSL uplink:

router=<router ip or dns name>
public_ip="`snmptable -c public -v 2c -CH "${router}" .1.3.6.1.2.1.4.20 \
                               | awk ' $2 == 7 {print $1}'`"