Additional Listing

SPIRENT COMMUNICATIONS PLC

Application has been made to the Financial Services Authority and the London Stock Exchange for a total of 1,200,000 Ordinary shares of 3 ⅓p each in the capital of the Company to be admitted to the Official List and to trade. These shares are being reserved under a block listing and will be issued pursuant to the Spirent Stock Incentive Plan.

It is expected that admission will be granted on 17 May 2011 and trading will commence on 18 May 2011, or thereafter as the Ordinary shares are allotted.

When issued, these shares will rank pari passu with the existing Ordinary shares.

Rachel Whiting

Company Secretary