14-4 Cisco BPX 8600 Series Reference
SNMP Functions
Responses to Get (Get-Next) Requests
When an SNMP manager workstation sends an SNMP Get request packet to a BPX agent, it utilizes
the IP protocol for addressing. The request packet can use either a LAN interface for a locally
attached management workstation or a network interface for remote access. Each packet is in ASN.1
format, which is suitable for transmission via the UDP protocol. Once it arrives, the packet is
decoded to a Protocol Data Unit (PDU). This PDU is the SNMP internal packet structure.
A PDU consists of one or more variables requested by the manager. The PDU’s community string is
validated for correct access permissions, then the requested variables are collected within an SNMP
varbind list for processing.
For each variable in the request message, the agent calls a user-defined test function that makes sure
the requested variable exists. If the test confirms the existence of the variable, the agent calls a
user-defined get function to gain access to the BPX database for the specified variable. The get
function is appropriate for the type of request (Get or Get-Next).
A get function can read either a single scalar value or a single column entry from the database row.
The user-defined get-next function provides a way to read a table of unknown elements. The get-next
function returns the lexicographically next variable in the table with respect to the next variable. This
mechanism lets the manager sequentially retrieve the entire table.
The test and get functions result in a Get response packet. If an error occurs, the appropriate error
code is encoded in ASN.1 format and placed in the packet. If no errors occur, the returned values are
encoded and placed in the response packet. The response packet goes to the workstation that
originated the Get request.
ATM Set Requests
SNMP Set requests support the ATM functions in the following list. Refer to the Cisco WAN
Switching Command Reference for command descriptions.
• Add ATM connection (addcon)
• Delete ATM connection (delcon)
• Up ATM connection (upcon)
• Down ATM connection (dncon)
• Modify ATM connection (cnfrcon, cnfcos, cnfpref, cnfrcon)
• Test ATM connections (tstcon, tstdelay)
SNMP Set requests can implement the following BPX commands on ATM ports:
• Up ATM port (upfrport)
• Down ATM port (dnfrport)
• Modify ATM port (cnffrport)
