|A quick search on google shows no information on a 0xb9 router. I suspect that is not actually it's model. Typically, most SOHO Router's have a label on the underside that shows the model number. Also, somewhere on the unit will be the brand name (manufacturer's name).|
This is the information you need to search for a manual.
If the router you have is so old, or so obscure that there is no manual available for it then the simple solution is, buy a new router and replace the old junker.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.