Customizing SNMP MIBs for Gets and Traps in SR Linux#
SR Linux version 24.10.1 introduces a customizable SNMP framework allowing you to define your own SNMP management information bases (MIBs) for gets and traps. This same framework powers SR Linux's built-in MIBs and traps, offering flexibility that customizes SNMP MIBs to the specific requirements for your network.
The framework defines:
- Mapping files (YAML): To define MIB tables and object identifiers (OIDs).
- Conversion scripts (uPython): To process data from the management server via gNMI and convert it for SNMP.
SR Linux Built-In MIBs for Gets#
Built-in MIB mappings are defined in the configuration file available on the SR Linux's file system:
A simple list of supported OIDs for monitoring is in /etc/opt/srlinux/snmp/numbers.txt, and a detailed list with script information is in /etc/opt/srlinux/snmp/exportedOids when an / system snmp access-group is configured. These files are created at runtime when the SNMP server is started.
Table Definitions#
The table definition YAML file describes the framework components used to define a particular MIB table. Take the if_mib.yaml file for example, it maps interface-related data to standard MIB tables such as ifTable, ifXTable, and ifStackTable.
You can list the contents of this file with cat /opt/srlinux/snmp/scripts/if_mib.yaml and it is below for reference:
if_mib.yaml Definition File
#- This is the mapping for interfaces and subinterfaces. It defines MIB tables ifTable, ifXTable and ifStackTable.
paths:
- /interface/
- /interface/ethernet
- /interface/lag
- /interface/statistics
- /interface/transceiver
- /interface/subinterface/
- /interface/subinterface/statistics
python-script: if_mib.py
enabled: true
debug: false
tables:
- name: ifTable
enabled: true
oid: 1.3.6.1.2.1.2.2
indexes:
- name: ifIndex
oid: 1.3.6.1.2.1.2.2.1.1
syntax: integer
columns:
- name: ifIndex
oid: 1.3.6.1.2.1.2.2.1.1
syntax: integer
- name: ifDescr
oid: 1.3.6.1.2.1.2.2.1.2
syntax: octet string
- name: ifType
oid: 1.3.6.1.2.1.2.2.1.3
syntax: integer
- name: ifMtu
oid: 1.3.6.1.2.1.2.2.1.4
syntax: integer
- name: ifSpeed
oid: 1.3.6.1.2.1.2.2.1.5
syntax: gauge32
- name: ifPhysAddress
oid: 1.3.6.1.2.1.2.2.1.6
syntax: octet string
binary: true
- name: ifAdminStatus
oid: 1.3.6.1.2.1.2.2.1.7
syntax: integer
- name: ifOperStatus
oid: 1.3.6.1.2.1.2.2.1.8
syntax: integer
- name: ifLastChange
oid: 1.3.6.1.2.1.2.2.1.9
syntax: timeticks
- name: ifInOctets
oid: 1.3.6.1.2.1.2.2.1.10
syntax: counter32
- name: ifInUcastPkts
oid: 1.3.6.1.2.1.2.2.1.11
syntax: counter32
- name: ifInNUcastPkts
oid: 1.3.6.1.2.1.2.2.1.12
syntax: counter32
- name: ifInDiscards
oid: 1.3.6.1.2.1.2.2.1.13
syntax: counter32
- name: ifInErrors
oid: 1.3.6.1.2.1.2.2.1.14
syntax: counter32
- name: ifInUnknownProtos
oid: 1.3.6.1.2.1.2.2.1.15
syntax: counter32
- name: ifOutOctets
oid: 1.3.6.1.2.1.2.2.1.16
syntax: counter32
- name: ifOutUcastPkts
oid: 1.3.6.1.2.1.2.2.1.17
syntax: counter32
- name: ifOutNUcastPkts
oid: 1.3.6.1.2.1.2.2.1.18
syntax: counter32
- name: ifOutDiscards
oid: 1.3.6.1.2.1.2.2.1.19
syntax: counter32
- name: ifOutErrors
oid: 1.3.6.1.2.1.2.2.1.20
syntax: counter32
- name: ifOutQLen
oid: 1.3.6.1.2.1.2.2.1.21
syntax: gauge32
- name: ifSpecific
oid: 1.3.6.1.2.1.2.2.1.22
syntax: object identifier
- name: ifXTable
enabled: true
oid: 1.3.6.1.2.1.31.1.1
augment: ifTable
columns:
- name: ifName
oid: 1.3.6.1.2.1.31.1.1.1.1
syntax: octet string
- name: ifInMulticastPkts
oid: 1.3.6.1.2.1.31.1.1.1.2
syntax: counter32
- name: ifInBroadcastPkts
oid: 1.3.6.1.2.1.31.1.1.1.3
syntax: counter32
- name: ifOutMulticastPkts
oid: 1.3.6.1.2.1.31.1.1.1.4
syntax: counter32
- name: ifOutBroadcastPkts
oid: 1.3.6.1.2.1.31.1.1.1.5
syntax: counter32
- name: ifHcInOctets
oid: 1.3.6.1.2.1.31.1.1.1.6
syntax: counter64
- name: ifHcInUcastPkts
oid: 1.3.6.1.2.1.31.1.1.1.7
syntax: counter64
- name: ifHcInMulticastPkts
oid: 1.3.6.1.2.1.31.1.1.1.8
syntax: counter64
- name: ifHcInBroadcastPkts
oid: 1.3.6.1.2.1.31.1.1.1.9
syntax: counter64
- name: ifHcOutOctets
oid: 1.3.6.1.2.1.31.1.1.1.10
syntax: counter64
- name: ifHcOutUcastPkts
oid: 1.3.6.1.2.1.31.1.1.1.11
syntax: counter64
- name: ifHcOutMulticastPkts
oid: 1.3.6.1.2.1.31.1.1.1.12
syntax: counter64
- name: ifHcOutBroadcastPkts
oid: 1.3.6.1.2.1.31.1.1.1.13
syntax: counter64
- name: ifLinkUpDownTrapEnable
oid: 1.3.6.1.2.1.31.1.1.1.14
syntax: integer
- name: ifHighSpeed
oid: 1.3.6.1.2.1.31.1.1.1.15
syntax: gauge32
- name: ifPromiscuousMode
oid: 1.3.6.1.2.1.31.1.1.1.16
syntax: integer
- name: ifConnectorPresent
oid: 1.3.6.1.2.1.31.1.1.1.17
syntax: integer
- name: ifAlias
oid: 1.3.6.1.2.1.31.1.1.1.18
syntax: octet string
- name: ifCounterDiscontinuityTime
oid: 1.3.6.1.2.1.31.1.1.1.19
syntax: timeticks
- name: ifStackTable
enabled: true
oid: 1.3.6.1.2.1.31.1.2
indexes:
- name: ifStackHigherLayer
oid: 1.3.6.1.2.1.31.1.2.1.1
syntax: integer
- name: ifStackLowerLayer
oid: 1.3.6.1.2.1.31.1.2.1.2
syntax: integer
columns:
- name: ifStackStatus
oid: 1.3.6.1.2.1.31.1.2.1.3
syntax: integer
scalars:
- name: ifNumber
enabled: true
oid: 1.3.6.1.2.1.2.1
syntax: integer
- name: ifTableLastChange
enabled: true
oid: 1.3.6.1.2.1.31.1.5
syntax: timeticks
The table definition file has the following important top level fields:
paths: Specifies the gNMI paths for retrieving data.python-script: References the Python script used for data conversion.tables: Lists MIB tables, their structure, and their OIDs.scalars: Defines scalar OIDs.
You can see the list of MIB table definitions in the tables list, where each table has the following structure:
name: Specifies the name of the SNMP table. This is used for identification and reference in the SNMP configuration.enabled: Defines whether the table is active (true) or inactive (false).oid: The base OID for the table. All rows and columns in the table are extensions of this base OID.indexes: Indexes uniquely identify rows in the table. Each index maps a specific OID to a value that differentiates rows. A list of column definitions that serve as unique identifiers for rows.name: The name of the index column.oid: The OID for the index.syntax: The data type of the index value.
columns: Columns represent attributes or properties for each row in the table. Each column is defined with an OID and a data type.name: The name of the column.oid: The OID for the column.syntax: The data type of the column's value.binary: (optional) Indicates if the value is base64-encoded.enabled: (optional) Enables or disables the column.
The syntax field in SNMP table and scalar definitions specifies the data type of the OID value. Each data type maps to a specific ASN.1 type, defining how the data is represented and transmitted in SNMP operations. Below is a detailed explanation of the supported data types.
Data Types
octet string: Represents a sequence of octets (bytes). Commonly used for textual information (e.g., names, descriptions) or raw binary data. E.g:ifDescr.integer / integer32: Represents a signed 32-bit integer. Used for numeric attributes like counters, states, or enumerations. E.g:ifType,ifAdminStatus,ifOperStatus.unsigned / unsigned32: Represents an unsigned 32-bit integer. E.g: values that should not be negative like counts or identifiers.counter / counter32: Represents a counter that increments over time and wraps back to 0 when it exceeds the maximum value (4,294,967,295). E.g:ifInOctets,ifOutOctets.counter64: Represents a 64-bit counter for high-capacity devices or metrics with large values. E.g:ifHCInOctets,ifHCOutOctets.gauge / gauge32: Represents a non-negative integer that can increase or decrease but cannot wrap. E.gifSpeed.timeticks: Represents time in hundredths of a second since a device was last initialized or restarted. E.g:ifLastChange.ipaddress: Represents an IPv4 address as a 32-bit value. Stored and transmitted in network byte order (big-endian).object identifier: Represents an OID as a series of numbers identifying objects or properties in the SNMP tree.bits: Represents a sequence of bits, often used to define flags or multiple binary states.
Creating Custom MIBs#
You can create custom MIB definitions following these steps:
- Define the mapping file: Specify paths, tables, scalars, and their structure in YAML.
- Write the conversion script: Implement a
snmp_mainfunction in Python that processes the input JSON and generates SNMP objects. - Add the mapping file to the list of table definitions to
/etc/opt/srlinux/snmp/snmp_files_config.yaml.
Location of Built-in and Custom SNMP Framework Files
The user-defined MIB definitions and files with the associated scripts are stored in /etc/opt/srlinux/snmp directory, while the built-in MIB definitions are stored in /opt/srlinux/snmp directory.
Input JSON Format#
The SNMP framework is powered by the underlying SR Linux's gNMI infrastructure. The paths you define in the table mapping file will retrieve the data that the conversion script will use to create the SNMP MIB tables.
Note that the paths you define in the mapping file are non-recursive; this means that the returned data will be limited to the immediate children of the path you specify. To recursively retrieve data from a path, add ... to the end of the path, e.g. /interface/ethernet/....
The Python script receives data in JSON format, including global SNMP information and the gNMI query results. Here is an example of a payload the if_mib.py script receives.
{
"_snmp_info_": {
"boottime": "2024-11-11T16:42:44Z",
"datetime": "2024-11-15T19:23:29Z",
"debug": false,
"is-cold-boot": false,
"network-instance": "mgmt",
"platform-type": "7220 IXR-D2",
"script": "if_mib.yaml",
"sysobjectid": "1.3.6.1.4.1.6527.1.20.22",
"sysuptime": 35524500,
"paths": [
"/interface",
"/interface/ethernet",
"/interface/lag",
"/interface/statistics",
"/interface/transceiver",
"/interface/subinterface",
"/interface/subinterface/statistics"
],
"scalars": [
"ifNumber",
"ifTableLastChange"
],
"tables": [
"ifTable",
"ifXTable",
"ifStackTable"
]
},
"interface": [
{
"name": "ethernet-1/1",
"admin-state": "enable",
"forwarding-complex": 0,
"forwarding-mode": "store-and-forward",
"ifindex": 16382,
"last-change": "2024-11-11T16:42:50.815Z",
"linecard": 1,
"loopback-mode": "none",
"mtu": 9232,
"oper-state": "up",
"tpid": "srl_nokia-interfaces-vlans:TPID_0X8100",
"vlan-tagging": false,
"ethernet": {
"dac-link-training": false,
"hw-mac-address": "1A:5E:00:FF:00:01",
"lacp-port-priority": 32768,
"port-speed": "25G"
},
"statistics": {
"carrier-transitions": 0,
"in-broadcast-packets": 0,
"in-discarded-packets": 0,
"in-error-packets": 0,
"in-fcs-error-packets": 0,
"in-multicast-packets": 11946,
"in-octets": 2103314,
"in-packets": 11946,
"in-unicast-packets": 0,
"out-broadcast-packets": 0,
"out-discarded-packets": 0,
"out-error-packets": 0,
"out-mirror-octets": 0,
"out-mirror-packets": 0,
"out-multicast-packets": 11842,
"out-octets": 2096034,
"out-packets": 11842,
"out-unicast-packets": 0
},
"transceiver": {
"ddm-events": true,
"forward-error-correction": "disabled",
"oper-down-reason": "not-present",
"oper-state": "down",
"tx-laser": false
}
},
{
"name": "ethernet-1/10",
"admin-state": "disable",
"forwarding-complex": 0,
"forwarding-mode": "store-and-forward",
"ifindex": 311294,
"last-change": "2024-11-11T16:42:47.867Z",
"linecard": 1,
"loopback-mode": "none",
"oper-down-reason": "port-admin-disabled",
"oper-state": "down",
"ethernet": {
"dac-link-training": false,
"hw-mac-address": "1A:5E:00:FF:00:0A",
"port-speed": "25G"
},
"transceiver": {
"ddm-events": false,
"forward-error-correction": "disabled",
"oper-down-reason": "not-present",
"oper-state": "down",
"tx-laser": false
}
},
{
// ...
},
}
Output JSON Format#
The script outputs JSON containing tables and scalars.
{
"tables": {
"ifTable": [
{
"path": "/interface[name=ethernet-1/1]",
"objects": {
"ifIndex": 16382,
"ifDescr": "ethernet-1/1",
"ifType": 6,
"ifMtu": 9232,
"ifSpeed": 4294967295,
"ifPhysAddress": "0x1A5E00FF0001",
"ifAdminStatus": 1,
"ifOperStatus": 1,
"ifLastChange": 600,
"ifInOctets": 2103314,
"ifInUcastPkts": 0,
"ifInNUcastPkts": 11946,
"ifInDiscards": 0,
"ifInErrors": 0,
"ifInUnknownProtos": 0,
"ifOutOctets": 2096034,
"ifOutUcastPkts": 0,
"ifOutNUcastPkts": 11842,
"ifOutDiscards": 0,
"ifOutErrors": 0,
"ifOutQLen": 0,
"ifSpecific": "0.0"
}
},
{
...
}
]
},
"scalars": {
"ifNumber": 58,
"ifTableLastChange": 600
}
}
Python Script#
The script entry point is a function called snmp_main that takes a JSON string as input and returns a JSON string.
Refer to the built-in scripts as examples. The /opt/srlinux/snmp/scripts/utilities.py script contains some useful helper functions to perform various checks and common type conversions.
SR Linux Built-In Traps#
Traps are defined with mapping files that look similar to the MIB files, but include additional parameters for triggers and variable bindings. As you have seen in the beginning of this document, the traps mapping files are listed in the global /opt/srlinux/snmp/snmp_files_config.yaml.
A list of OIDs available for traps is in /etc/opt/srlinux/snmp/installedTraps when a trap-group is configured. This file is created at runtime when the SNMP server is started.
Trap Definitions#
The trap definition YAML file has exactly the same top level elements as the table definition file but instead of tables the file contains traps top-level list. Here is the contents of the /opt/srlinux/snmp/scripts/rfc3418_traps.yaml mapping file that defines the traps as per RFC 3418:
rfc3418_traps.yaml definition file
python-script: rfc3418_traps.py
enabled: true
debug: false
traps:
- name: coldStart
enabled: true
oid: 1.3.6.1.6.3.1.1.5.1
startup: true
triggers:
- /platform/chassis/last-booted
- name: warmStart
enabled: true
oid: 1.3.6.1.6.3.1.1.5.2
startup: true
triggers:
- /platform/chassis/last-booted
- name: linkDown
enabled: true
oid: 1.3.6.1.6.3.1.1.5.3
triggers:
- /interface/oper-state
- /interface/subinterface/oper-state
context:
- /interface
- /interface/subinterface
data:
- indexes:
- name: ifIndex
syntax: integer
objects:
- name: ifIndex
oid: 1.3.6.1.2.1.2.2.1.1
syntax: integer
- name: ifAdminStatus
oid: 1.3.6.1.2.1.2.2.1.7
syntax: integer
- name: ifOperStatus
oid: 1.3.6.1.2.1.2.2.1.8
syntax: integer
- name: ifName # non-standard, but useful
enabled: true
oid: 1.3.6.1.2.1.31.1.1.1.1
syntax: octet string
optional: true
- name: linkUp
enabled: true
oid: 1.3.6.1.6.3.1.1.5.4
triggers:
- /interface/oper-state
- /interface/subinterface/oper-state
context:
- /interface
- /interface/subinterface
data:
- indexes:
- name: ifIndex
syntax: integer
objects:
- name: ifIndex
oid: 1.3.6.1.2.1.2.2.1.1
syntax: integer
- name: ifAdminStatus
oid: 1.3.6.1.2.1.2.2.1.7
syntax: integer
- name: ifOperStatus
oid: 1.3.6.1.2.1.2.2.1.8
syntax: integer
- name: ifName # non-standard, but useful
enabled: true
oid: 1.3.6.1.2.1.31.1.1.1.1
syntax: octet string
optional: true
- name: authenticationFailure
enabled: true
hardcoded: true
oid: 1.3.6.1.6.3.1.1.5.5
Besides the common name, enabled and oid fields, the traps object has the following fields:
triggers: Specifies paths that trigger the trap.context: Additional paths to fetch data for the trap.data: Defines variable bindings included in the trap.
Creating Custom Traps#
To define custom traps:
- Define the mapping file: Define the trap triggers, contexts, and variable bindings in YAML.
- Write the conversion script: Implement trigger events and generate trap data in the
snmp_mainfunction. - Add the mapping file to the list of trap definitions to
/etc/opt/srlinux/snmp/snmp_files_config.yaml.
Input JSON Format#
The Python script receives a JSON object containing trap triggers and context data.
{
"_snmp_info_": {
"boottime": "2024-11-11T16:42:44Z",
"datetime": "2024-11-15T21:30:25Z",
"debug": true,
"is-cold-boot": false,
"network-instance": "mgmt",
"platform-type": "7220 IXR-D2",
"script": "rfc3418_traps.yaml",
"sysobjectid": "1.3.6.1.4.1.6527.1.20.22",
"sysuptime": 36286100,
"trigger": "/interface[name=ethernet-1/1]",
"paths": [
"/interface[name=ethernet-1/1]",
"/interface[name=ethernet-1/1]/subinterface"
]
},
"_trap_info_": [
{
"name": "linkDown",
"new-value": "up",
"old-value": "down",
"trigger": "/interface/oper-state",
"xpath": "/interface[name=ethernet-1/1]/oper-state"
},
{
"name": "linkUp",
"new-value": "up",
"old-value": "down",
"trigger": "/interface/oper-state",
"xpath": "/interface[name=ethernet-1/1]/oper-state"
}
],
"interface": [
{
"name": "ethernet-1/1",
"admin-state": "enable",
"forwarding-complex": 0,
"forwarding-mode": "store-and-forward",
"ifindex": 16382,
"last-change": "2024-11-15T21:30:25.701Z",
"linecard": 1,
"loopback-mode": "none",
"mtu": 9232,
"oper-state": "up",
"tpid": "srl_nokia-interfaces-vlans:TPID_0X8100",
"vlan-tagging": false,
"subinterface": [
{
"index": 0,
"admin-state": "disable",
"ifindex": 1,
"ip-mtu": 1500,
"last-change": "2024-11-15T21:24:47.797Z",
"name": "ethernet-1/1.0",
"oper-down-reason": "admin-disabled",
"oper-state": "down",
"type": "routed"
}
]
}
]
}
Output JSON Format#
The script returns a list of traps.
{
"traps": [
{
"trap": "linkUp",
"path": "/interface[name=ethernet-1/1]",
"indexes": {
"ifIndex": 16382
},
"objects": {
"ifIndex": 16382,
"ifAdminStatus": 1,
"ifOperStatus": 1,
"ifName": "ethernet-1/1"
}
}
]
}
Python Script#
The script entry point is a function called snmp_main that takes a JSON string as input and returns a JSON string.
Refer to the built-in scripts as examples. The /opt/srlinux/snmp/scripts/utilities.py script contains some useful helper functions to perform various checks and common type conversions.
Directory Structure for Custom Files#
Place user-defined files in /etc/opt/srlinux/snmp.
Changes to mapping files and scripts are not automatically read by the SNMP server, a restart of the SNMP server is required.
Debugging and Troubleshooting#
Debug files are generated in /tmp/snmp_debug/$NETWORK_INSTANCE when debug: true is set in the YAML configuration file.
- For MIBs: check
/etc/opt/srlinux/snmp/exportedOidsfor your OIDs and make sure an/ system snmp access-groupis configured. - For traps: check
/etc/opt/srlinux/snmp/installedTrapsfor your traps and make sure a/ system snmp trap-groupis configured. - Input/output logs: Check
.json_input,.json_output,.consoleand.errorfiles for debugging script execution. The.consolefiles contain output printed by the scripts and the.errorfiles contain mapping and scripts errors. - Path data: Inspect debug outputs for issues in path retrieval.
Examples#
gRPCServer MIB#
Let's add a custom SNMP MIB to SR Linux at runtime, no feature requests, no software upgrades, by creating a gRPC server SNMP MIB 🤪.
Table Definition#
Add a new table definition to /etc/opt/srlinux/snmp/scripts/grpc_mib.yaml.
This MIB has a single index gRPCServerName and 6 columns; the gRPC server network instance, its admin and operational states, the number of accepted and rejected RPCs and the last time an RPC was accepted.
All of these fields can be mapped from leafs that are found under the XPath /system/grpc-server/...
###########################################################################
# Description:
#
# Copyright (c) 2024 Nokia
###########################################################################
# yaml-language-server: $schema=./table_definition_schema.json
paths:
- /system/grpc-server/...
python-script: grpc_mib.py
enabled: true
debug: true
tables:
- name: gRPCServerTable
enabled: true
oid: 1.3.6.1.4.1.6527.115.114.108.105.110.117.120
indexes:
- name: gRPCServerName
oid: 1.3.6.1.4.1.6527.115.114.108.105.110.117.120.1.1
syntax: octet string
columns:
- name: grpcServerNetworkInstance
oid: 1.3.6.1.4.1.6527.115.114.108.105.110.117.120.1.2
syntax: octet string
- name: grpcServerAdminState
oid: 1.3.6.1.4.1.6527.115.114.108.105.110.117.120.1.3
syntax: integer
- name: grpcServerOperState
oid: 1.3.6.1.4.1.6527.115.114.108.105.110.117.120.1.4
syntax: integer
- name: grpcServerAccessRejects
oid: 1.3.6.1.4.1.6527.115.114.108.105.110.117.120.1.5
syntax: integer
- name: grpcServerAccessAccepts
oid: 1.3.6.1.4.1.6527.115.114.108.105.110.117.120.1.6
syntax: integer
- name: grpcServerLastAccessAccept
oid: 1.3.6.1.4.1.6527.115.114.108.105.110.117.120.1.7
syntax: timeticks
Python Script#
The YAML file references a Python script called grpc_mib.py. It must be placed in the same directory as the grpc_mib.yaml file.
The script is fairly simple; it grabs the JSON input and sets some global SNMP information such as the system boot time (useful for calculating time ticks values). After that, it iterates over the list of gRPC servers in the input JSON and set each server's columns values (with the correct format) in the prepared output dict. Finally it returns the output dict as a JSON blob.
#!/usr/bin/python
###########################################################################
# Description:
#
# Copyright (c) 2024 Nokia
###########################################################################
import json
import utilities
SERVER_ADMIN_STATUS_UP = 1
SERVER_ADMIN_STATUS_DOWN = 2
IF_OPER_STATUS_UP = 1
IF_OPER_STATUS_DOWN = 2
# maps the gNMI admin status value to its corresponding SNMP value
def convertAdminStatus(value: str):
if value is not None:
if value == "enable":
return SERVER_ADMIN_STATUS_UP
elif value == "disable":
return SERVER_ADMIN_STATUS_DOWN
# maps the gNMI oper status value to its corresponding SNMP value
def convertOperStatus(value: str):
if value is not None:
if value == "up":
return IF_OPER_STATUS_UP
elif value == "down":
return IF_OPER_STATUS_DOWN
#
# main routine
#
def snmp_main(in_json_str: str) -> str:
in_json = json.loads(in_json_str)
del in_json_str
# read in general info from the snmp server
snmp_info = in_json.get("_snmp_info_")
utilities.process_snmp_info(snmp_info)
# prepare the output dict
output = {"tables": {"gRPCServerTable": []}}
# Iterate over all grpc-server instances
grpc_servers = in_json.get("system", {}).get("grpc-server", [])
for server in grpc_servers:
# Extract required fields
name = server.get("name", "")
statistics = server.get("statistics", {})
access_rejects = statistics.get("access-rejects", 0)
access_accepts = statistics.get("access-accepts", 0)
last_access_accept = 0
# Grab the last-access-accept timestamp
_last_access = statistics.get("last-access-accept", False)
if _last_access:
ts = utilities.parse_rfc3339_date(_last_access)
# Convert it to timeTicks from boot time
last_access_accept = utilities.convertUnixTimeStampInTimeticks(ts)
# Append the object to the output
output["tables"]["gRPCServerTable"].append(
{
"objects": {
"gRPCServerName": name,
"grpcServerNetworkInstance": server.get("network-instance", ""),
"grpcServerAdminState": convertAdminStatus(
server.get("admin-state", "")
),
"grpcServerOperState": convertOperStatus(server.get("oper-state")),
"grpcServerAccessRejects": access_rejects,
"grpcServerAccessAccepts": access_accepts,
"grpcServerLastAccessAccept": last_access_accept,
}
}
)
return json.dumps(output)
Custom MIBs File#
Reference the YAML mapping file in the your snmp_files_config.yaml so that the SNMP server loads it.
SNMP Server Restart#
Restart the SNMP server process for it to load the new custom MIB definitions.
--{ running }--[ ]--
A:srl1# /tools system app-management application snmp_server-mgmt restart
/system/app-management/application[name=snmp_server-mgmt]:
Application 'snmp_server-mgmt' was killed with signal 9
/system/app-management/application[name=snmp_server-mgmt]:
Application 'snmp_server-mgmt' was restarted
Test Your New MIB#
You can test your new MIB using tools like snmpwalk.
Have a look at /tmp/snmp_debug to see the input and output JSON blobs when debug: true is set in the YAML configuration file.
There you have it: a user-defined SNMP MIB added to SR Linux at runtime, no feature request, no software upgrade needed.
gRPCServer Traps#
Similar to the SNMP MIB, let's add custom SNMP traps to SR Linux at runtime, no feature requests, no software upgrades, by creating a gRPC server SNMP trap 🤪. Traps are independent from MIBs and do not need a corresponding MIB that is used for SNMP gets.
Trap Definitions#
Add a new trap definitions to /etc/opt/srlinux/snmp/scripts/grpc_traps.yaml.
Two traps are defined:
- gRPCServerDown: sent when a gRPC server goes down.
- gRPCServerUp: sent when a gRPC server comes up, including at startup.
Both of these traps are triggered from the /system/grpc-server/oper-state XPath.
###########################################################################
# Description:
#
# Copyright (c) 2024 Nokia
###########################################################################
# yaml-language-server: $schema=./trap_definition_schema.json
python-script: grpc_traps.py
enabled: true
debug: true
traps:
- name: gRPCServerDown
enabled: true
startup: true
oid: 1.3.6.1.4.1.6527.115.114.108.105.110.117.122
enterprise: 1.3.6.1.4.1.6527.1.20
triggers:
- /system/grpc-server/oper-state
context:
- /system/grpc-server/...
data:
- objects: # this object is a scalar, does not use an index
- name: gRPCServerName
oid: 1.3.6.1.4.1.6527.115.114.108.105.110.117.120.1.1
syntax: octet string
- name: gRPCServerUp
enabled: true
startup: true
oid: 1.3.6.1.4.1.6527.115.114.108.105.110.117.123
enterprise: 1.3.6.1.4.1.6527.1.20
triggers:
- /system/grpc-server/oper-state
context:
- /system/grpc-server/...
data:
- objects: # this object is a scalar, does not use an index
- name: gRPCServerName
oid: 1.3.6.1.4.1.6527.115.114.108.105.110.117.120.1.1
syntax: octet string
Python Script#
The YAML file references a Python script called grpc_traps.py. It must be placed in the same directory as the grpc_mib.yaml file.
The script is fairly simple; it grabs the JSON input and looks for the gRPC server name to add as a variable binding. You can add additional variable bindings to traps that are relevant if you want, but in this case we only need one for the server name. Finally it returns the output dict as a JSON blob.
###########################################################################
# Description:
#
# Copyright (c) 2025 Nokia
###########################################################################
import json
from collections import OrderedDict
import re
import utilities
# list of traps that will be echoed back to the client
traps_list_db: list = []
def parseGrpcServerKeys(xpath: str):
# retrieve the name of the grpc-server from the xpath
name_pattern = re.compile(r"[^\]]+\[([^\[\]=]+?)=([^\]]+)\]")
matches = name_pattern.match(xpath)
if matches is not None:
return matches.group(2)
return None
def gRPCServerUpgRPCServerUpDownTrap(grpc_servers: list, trap: dict, value) -> None:
filter_key = parseGrpcServerKeys(trap.get("xpath", ""))
if filter_key is None:
raise ValueError(f"Can't look for a grpc-server without an xpath")
# loop over all grpc-servers, filter the ones that match the xpath
for server in grpc_servers:
server_name = server.get("name", "") # key
if server_name != filter_key:
continue
# only report the grpc-servers that have the correct oper-state (unless force flag was used)
if not utilities.is_forced_simulated_trap():
oper_state = server.get("oper-state", "")
if value is not None and oper_state != value:
continue
row = OrderedDict()
objects = OrderedDict()
objects["gRPCServerName"] = server_name
row["trap"] = trap.get("name", "")
row["indexes"] = OrderedDict() # no indexes to report
row["objects"] = objects
traps_list_db.append(row)
#
# main routine
#
def snmp_main(in_json_str: str) -> str:
global traps_list_db
in_json = json.loads(in_json_str)
# read in general info from the snmp server
snmp_info = in_json.get("_snmp_info_")
utilities.process_snmp_info(snmp_info)
# read in info about the traps that will be triggered in this request (depending on the trigger)
trap_info = in_json.get("_trap_info_", [])
system = in_json.get("system", {})
grpc_servers = system.get("grpc-server", [])
# loop over all traps in this request
for trap in trap_info:
name = trap.get("name", "")
trigger = trap.get("trigger", "")
newValue = trap.get("new-value", "")
if name == "gRPCServerDown":
if newValue == "down" or utilities.is_forced_simulated_trap():
gRPCServerUpgRPCServerUpDownTrap(grpc_servers, trap, newValue)
elif name == "gRPCServerUp":
if newValue == "up" or utilities.is_forced_simulated_trap():
gRPCServerUpgRPCServerUpDownTrap(grpc_servers, trap, newValue)
else:
raise ValueError(f"Unknown trap {name} with trigger {trigger}")
response: dict = {}
response["traps"] = traps_list_db
return json.dumps(response)
Custom Traps File#
Reference the YAML mapping file in the your snmp_files_config.yaml so that the SNMP server loads it.
SNMP Server Restart#
Restart the SNMP server process for it to load the new custom traps.
--{ running }--[ ]--
A:srl1# /tools system app-management application snmp_server-mgmt restart
/system/app-management/application[name=snmp_server-mgmt]:
Application 'snmp_server-mgmt' was killed with signal 9
/system/app-management/application[name=snmp_server-mgmt]:
Application 'snmp_server-mgmt' was restarted
Test Your New Traps#
Test your new traps by sending them from SR Linux.
--{ running }--[ ]--
A:srl1# /tools system snmp trap gRPCServerDown force trigger "/system/grpc-server[name=mgmt]/oper-state"
/:
Trap gRPCServerDown was sent
--{ running }--[ ]--
A:srl1# /tools system snmp trap gRPCServerUp force trigger "/system/grpc-server[name=mgmt]/oper-state"
/:
Trap gRPCServerUp was sent
You can see the traps being received on a Unix host using tools like snmptrapd.
Have a look at /tmp/snmp_debug to see the input and output JSON blobs when debug: true is set in the YAML configuration file.
Input JSON Blob#
Output JSON Blob#
There you have it: user-defined SNMP traps added to SR Linux at runtime, no feature request, no software upgrade needed.
MIB and Trap Lab Example#
We created a lab that implements this custom gRPC server MIB and traps that you can deploy locally or in Codespaces to try it out.
Conclusion#
The SR Linux customizable SNMP framework allows you to define your own SNMP MIBs for gets and traps that customize SNMP functionalities to your specific requirements at runtime, no feature request, no software upgrade needed.