I/G/D/C/B/A-Series SNMP Polling for Port Speed/Duplex/Negotiation

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Article ID: 14477 

C5, C3, C2-Series
B5, B3, B2-Series
A4, A2-Series 

MIB OIDs to be polled to determine the port speed and port duplex settings used whenever port negotiation is disabled, and to determine the corresponding port negotiation setting.
How to update these OIDs using an SNMP-based Mib Tool (e.g. NetSight Console). 

Any given port's speed and duplex setting - which, due to the effects of auto-negotiation, may not be the same as the operating speed and duplex - may be monitored via the 'ifMauDefaultType=' OID referenced in 5298

The resulting Formatted Values most likely displayed for any given port instance are... 

dot3MauType10BaseTHD     [10, "UTP MAU, half duplex mode"]
dot3MauType10BaseTFD [11, "UTP MAU, full duplex mode"]
dot3MauType10BaseFLHD [12, "async fiber MAU, half duplex mode"]
dot3MauType10BaseFLFD [13, "async fiber MAU, full duplex mode"]
dot3MauType100BaseTXHD [15, "2 pair category 5 UTP, half duplex mode"]
dot3MauType100BaseTXFD [16, "2 pair category 5 UTP, full duplex mode"]
dot3MauType100BaseFXHD [17, "X fiber over PMT, half duplex mode"]
dot3MauType100BaseFXFD [18, "X fiber over PMT, full duplex mode"]
dot3MauType100BaseT2HD [19, "2 pair category 3 UTP, half duplex mode"]
dot3MauType100BaseT2FD [20, "2 pair category 3 UTP, full duplex mode"]
dot3MauType1000BaseXFD [22, "PCS/PMA, unknown PMD, full duplex mode"]
dot3MauType1000BaseLXFD [24, "Fiber over long-wavelength laser, full duplex mode"]
dot3MauType1000BaseSXFD [26, "Fiber over short-wavelength laser, full duplex mode"]
dot3MauType1000BaseTFD [30, "Four-pair Category 5 UTP, full duplex mode"]

Because ifMauDefaultType supports read/write capability, the speed/duplex may be changed for a port (within a range supported by the port) by setting that port's Raw Value to the OID path value (based from 'dot3MauType=') which will yield the desired hard-set speed/duplex behavior (4674). The correct OID path value representing "dot3MauType.<instance>" is constructed using the instance number listed above after the opening square bracket. 

For example, a 10/100 port would show up with a ifMauDefaultType Formatted Value of "dot3MauType10BaseTHD" (10HD) by default. To change the port to operate at 100FD (equivalent to issuing the CLI commands 'set port speed <port#> 100' and 'set port duplex <port#> full') whenever port negotiation is disabled, you'd effectively need to change the Formatted Value to read as "dot3MauType100BaseTXFD", but to do that, you would actually change the Raw Value to1., representing the 16th instance of the dot3MauType OID. Since most of this OID string is already present in the Raw Value field, you'll only need to change the last octet. If you receive a "Data Type Mismatch" error, you are trying to change the Formatted Value rather than the Raw Value. 

Port negotiation may be viewed and toggled by targeting the correct port instance of read/write OID 'ifMauAutoNegAdminStatus=' (also referenced in 5298). Raw Values of 2 or 1 (equivalent to issuing the CLI commands 'set port negotiation <port#> disable' or 'set port negotiation <port#> enable') yield, respectively, Formatted Values of "disabled" or "enabled" (default). 

Note: A port's operating speed and duplex state is not stored/retrievable in any SNMP MIB OID.
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Posted 4 years ago

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