Discover interface optics

In the SNMP driver, we discover transceivers in the self._get_interface_transceiver_types() function, called from get_my_basic_info() around line 1010. We use the MAU MIB to get transciever information.

Using MAU-MIB

The MAU (Media Access Unit) MIB is the standard way of describing media types, ie. transceivers. See the MIB definition at https://www.iana.org/assignments/ianamau-mib/ianamau-mib and the more readable version at https://mibs.observium.org/mib/MAU-MIB/

This MIB defines transceiver types for interface indeces. These types are defined as ‘OID’ formatted strings. E.g. a value of “.1.3.6.1.2.1.26.4.35” means a 10GBase-LR optical transceiver.

We call _get_interface_transceiver_types() to read the device mib at ifMauType (.1.3.6.1.2.1.26.2.1.1.3). This is parsed in _parse_mibs_if_mau_type() Here we read the return value, and this is parsed to an optic or transceiver type in _parse_and_set_mau_type()

“Interesting” types are defined in snmp/constants.py, see the variable mau_types. We primarily want to show optical transceivers. If a transceiver type of interest is present, we then assign a Transceiver() object to the Interface(). This is then displayed in the template _tpl_if_type_icons.html, as shown here:

{% if iface.transceiver %}
&nbsp;
<i class="fa-solid fa-bolt" aria-hidden="true"
    data-bs-toggle="tooltip"
    title="{{ iface.transceiver }} transceiver">
</i>
{% endif %}

Note: The return value from the call to read ifMauType are numbers defined by IANA in https://www.iana.org/assignments/ianamau-mib/ianamau-mib and # https://datatracker.ietf.org/doc/html/rfc3636 .

They indicate the transceiver type. All valid returns start with “.1.3.6.1.2.1.26.4.”

E.g. .1.3.6.1.2.1.26.2.1.1.3.**24.1** = OID: .1.3.6.1.2.1.26.4.35

24.1 is <if_index>.<sub-port>, ie interface 24. The return value “.1.3.6.1.2.1.26.4.35” is “10GBASE-LR”, per the definitions in the IF-MAU MIB.

Note

Some drivers augment or override the _get_interface_transceiver_types() call to run their own discovery.

Other thoughs

Not Implemented Yet

We can also look at this: entPhysicalClass (.1.3.6.1.2.1.47.1.1.1.1.5) for values 10 (Port)

.1.3.6.1.2.1.47.1.1.1.1.5.1006 = INTEGER: 10

followed by:

Use ‘entPhysicalDescr (‘.1.3.6.1.2.1.47.1.1.1.1.2’): .1.3.6.1.2.1.47.1.1.1.1.2.1006 = STRING: “Gigabit Ethernet Port” .1.3.6.1.2.1.47.1.1.1.1.2.1007 = STRING: “SFP-10Gbase-SR”

Some implementation show the optics type in the device description, but not all!

The interface index 1006 is type .1.3.6.1.4.1.9.12.3.1.10.151 and interface 1007 is type .1.3.6.1.4.1.9.12.3.1.9.76.3, defined as SFP10GSR See https://oid-base.com/get/1.3.6.1.4.1.9.12.3.1.9.76.3

entPhysicalVendorType (.1.3.6.1.2.1.47.1.1.1.1.3) can also be used:

.1.3.6.1.2.1.47.1.1.1.1.3.1006 = OID: .1.3.6.1.4.1.9.12.3.1.10.151: Cisco Entity VendorType OID MIB defines this as ” cevPortGESFP”, likely an empty SFP slot.
.1.3.6.1.2.1.47.1.1.1.1.3.1007 = OID: .1.3.6.1.4.1.9.12.3.1.9.76.3: defined by Cisco as “cevSFP10GSR”, ie 10g-SR

Note that the returned value is vendor-defined, i.e. complex to parse!