D-Link DIR-505 Manual page 19

Step 4 : U nder t he R outer S edngs s ec=on, t ype i n t he r outer´s n ew R outer I P A ddress a nd
Subnet M ask i n t he fi elds p rovided.
Step 5 : C lick S ave S eCngs t o s ave t he c urrent c onfigura=on.