I remember having seen this message. So should be TOS 5.1
Earlier TOS versions cannot be directly updated to TOS 5.1, and must be manually updated step by step in the following order: 5.0.120 -> 5.0.176 -> 5.1.24 -> 5.1.40（Or newer TOS version）
Earlier TOS versions cannot be directly updated to TOS 5.1, and must be manually updated step by step in the following order: 5.0.120 -> 5.0.176 -> 5.1.24 -> 5.1.40（Or newer TOS version）
Statistics: Posted by Rajesh — Today, 09:02