Thread: linking problem

I am getting the following errors when trying to compile my code:

DLLMain.obj : error LNK2001: unresolved external symbol "class BMLClient netClient" (?netClient@@3VBMLClient@@A)
Desktop\Walker26.dlc : fatal error LNK1120: 1 unresolved externals

the line that is causing it is :

Code:

int az = netClient.GetAzimuth();

netClient is declared as

Code:

extern BMLClient netClient;

in the same file

the original declaration is in another header file BMLDrawable.h:

Code:

class BMLDrawable: public osg::Drawable {
public:
	BMLDrawable();
	virtual ~BMLDrawable();

	virtual osg::Object* cloneType() const
	{
		return new BMLDrawable();
	}

	virtual osg::Object* clone(const osg::CopyOp&) const
	{
		return new BMLDrawable();
	}

	bool computeBound() const;
	virtual void drawImplementation(osg::State& state) const;
	
	
protected:
	BMLClient netClient;
};

GetAzimuth is declared as

Code:

 int GetAzimuth(void) { return m_nAzimuth; }

in the BMLClient class

is anyone familiar with what this error means?