SNMPv2 is a revised protocol that includes performance and manager-to-manager communication improvements to SNMP. SNMPv2 was introduced with RFC 1441, Introduction to version 2 of the Internet-standard Network Management Framework, but members of the IETF subcommittee could not agree on several sections of the SNMPv2 specification (primarily the protocol's security and administrative needs). Several attempts to achieve acceptance of SNMPv2 have been made by releasing experimental modified versions, commonly known as SNMPv2*, SNMPv2, SNMPv2u, SNMPv1+, and SNMPv1.5, which do not contain the disputed parts.

Community-based SNMPv2 (or SNMPv2c), which is defined in RFC 1901, Introduction to Community-based SNMPv2, is referred to as SNMPv2 because it is the most common implementation. The "c" stands for community-based security because SNMPv2c uses the same community strings as SNMPv1 for read and write access. SNMPv2 changes include the introduction of the following two new message types:

■ GetBulk message type: Used for retrieving large amounts of data, such as tables. This message reduces repetitive requests and replies, thereby improving performance.

■ InformRequest: Used to alert the SNMP manager of a specific condition. Unlike unacknowledged trap messages, InformRequest messages are acknowledged. A managed device sends an InformRequest to the NMS; the NMS acknowledges the receipt of the message by sending a Response message back to the managed device.

Another improvement of SNMPv2 over SNMPv1 is the addition of new data types with 64-bit counters because 32-bit counters were quickly overflowed by fast network interfaces.

On Cisco routers, Cisco IOS software release 11.3 and later versions implement SNMPv2. However, neither SNMPv1 nor SNMPv2 offers security features. Specifically, SNMPv1 and SNMPv2 can neither authenticate the source of a management message nor encrypt the message.

Because of the lack of security features, many SNMPvl and SNMPv2 implementations are limited to a read-only capability, reducing their usefulness to that of a network monitor.

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