CODEWITHSUNDEEP
snmpnet-snmpwebnms
Ravi
Ravi

Reputation: 71

maximum allowed length for read and write community for SNMPv2c

Can you please tell me the maximum length allowed for SNMPv2c read and write community .I didn't find any relevant doc which can provide description about the same .

Thanks -Ravi

Upvotes: 2

Views: 4603

Answers (3)

katoomba
katoomba

Reputation: 1

SNMP version 2c maximum community length on Cisco routers is 128 characters.

Upvotes: 0

Aniruddh Dikhit
Aniruddh Dikhit

Reputation: 682

The community based model also refers to the entries in the USM tables. Following the SNMP USM MIBs defined in RFC3414 the definition of usmUserName and usmSecurityName is as below which limits the user name to 32 characters. The textual convention SnmpAdminString itself is 255 Octet long

usmUserName      OBJECT-TYPE
    SYNTAX       SnmpAdminString (SIZE(1..32))
    MAX-ACCESS   not-accessible
    STATUS       current
    DESCRIPTION "A human readable string representing the name of
                 the user.

                 This is the (User-based Security) Model dependent
                 security ID.
                "
    ::= { usmUserEntry 2 }

usmUserSecurityName OBJECT-TYPE
    SYNTAX       SnmpAdminString
    MAX-ACCESS   read-only
    STATUS       current
    DESCRIPTION "A human readable string representing the user in
                 Security Model independent format.

                 The default transformation of the User-based Security
                 Model dependent security ID to the securityName and
                 vice versa is the identity function so that the
                 securityName is the same as the userName.
                "
    ::= { usmUserEntry 3 }

The Textual Convention usmUserSecurityName is defined in RFC3411

SnmpAdminString ::= TEXTUAL-CONVENTION
    DISPLAY-HINT "255t"
    STATUS       current
    DESCRIPTION "An octet string containing administrative
                 information, preferably in human-readable form.

..

                 Note that when this TC is used for an object that
                 is used or envisioned to be used as an index, then
                 a SIZE restriction MUST be specified so that the
                 number of sub-identifiers for any object instance
                 does not exceed the limit of 128, as defined by
                 [RFC3416].

                 Note that the size of an SnmpAdminString object is
                 measured in octets, not characters.
                "
    SYNTAX       OCTET STRING (SIZE (0..255))

On a Cisco switch/ router that also appears to be enforced when you are setting this via CLI.

Upvotes: 2

Gambit Support
Gambit Support

Reputation: 1463

There is no explicit limit on the length according to RFC 3584. The limits are going to be practical (message size, etc).

Upvotes: 1

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