Hello Liviu,
All certifications remain active for a period of two (2) years from the date earned. After this, certifications move to the Inactive status for a period of one (1) year. Certifications may be renewed while in the Active and Inactive statuses. You can renew all certifications earned on any given track by passing the highest level written exam on that track. For example, if you hold a JNCIS-ENT, JNCIP-ENT and JNCIE-ENT, you may renew these certifications by passing the JNCIP-ENT exam again while all certifications are in the Active or Inactive status.Recertification is only valid for certifications earned on the same track. For example, if you also hold a JNCIS-SEC, JNCIP-SEC and JNCIE-SEC, you would need to pass the JNCIP-SEC again to renew these certifications while they are Active or Inactive.
Once certifications move to the Expired status, after the one (1) year Inactive period, they cannot be renewed by passing the highest level written exam. In this case, candidates must begin from the bottom of the track and earn each certification again.
For more details about the Recertification process, please visit our website at http://www.juniper.net/us/en/training/certification/already-certified/recertification/
Regards,