SNMPv2c讀寫社區的最大允許長度

Question

您能否告訴我SNMPv2c讀寫社區允許的最大長度。我沒有找到任何可以提供相同描述的相關文檔。

由於 -Ravi

Answer 1

有根據RFC 3584 限將是實用的（消息大小，等等）上的長度沒有明確的限制。

Answer 2

基於社區的模型也引用了USM表中的條目。遵循RFC3414中定義的SNMP USM MIBs，usmUserName和usmSecurityName的定義如下，它將用戶名限制爲32個字符。該文本的約定SnmpAdminString本身是255字節長

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 } 

經過約定usmUserSecurityName在RFC3411

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

定義..

    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)) 

在Cisco交換機/路由器也顯得在通過CLI設置時強制執行。