EXHIBIT A

JOINT FILING AGREEMENT PURSUANT TO RULE 13d-1(k)(1)

This agreement is made pursuant to Rule 13d-1(k)(1) under the Securities Exchange Act of 1934 (the "Act") by and among the parties listed below, each referred to herein as a "Joint Filer." The Joint Filers agree that a statement of beneficial ownership as required by Section 13(d) of the Act and the Rules thereunder may be filed on each of their behalf on Schedule 13D or Schedule 13G, as appropriate, with respect to their ownership of the American Depositary Shares of 21Vianet Group, Inc. and that said joint filing may thereafter be amended by further joint filings. The Joint Filers state that they each satisfy the requirements for making a joint filing under Rule 13d-1. This Agreement may be executed in any number of counterparts, all of which taken together shall constitute one and the same instrument.

IN WITNESS WHEREOF, the undersigned hereby execute this Joint Filing Agreement as of the 30th day of August, 2012.

PENDRAGON SECURITIES LIMITED
By:	/s/ Mark Stoleson
	Mark Stoleson
	Director

LEGATUM CAPITAL LIMITED
By:	/s/ Mark Stoleson
	Mark Stoleson
	Director

LEGATUM GLOBAL HOLDINGS LIMITED
By:	/s/ Mark Stoleson
	Mark Stoleson
	Director

SENATE LIMITED, ACTING ON BEHALF OF THAT CERTAIN TRUST FORMED UNDER THE LAWS OF THE CAYMAN ISLANDS AS OF 1 JULY 1996
By:	/s/ Mark Stoleson
	Mark Stoleson
	Director