SNMP Explorer help

To start querying a network device:

• Click Add Device at the bottom of the sidebar.
• Enter a name and the host or IP address. The port defaults to 161.
• Choose the SNMP version. For v1 and v2c enter the community string; for v3 see SNMPv3 Configuration.
• Click Test Connection, then save.

Select the device in the sidebar to walk or query it. The dot next to each device turns green or red within about two seconds of launch, depending on whether the device answers.

The free version works with one device and includes Full Discovery, Single Query and trap reception.

Pro is an optional in-app upgrade. It adds unlimited devices, the Monitor view, walking selected MIBs, MIB import, shared credentials and CSV export. Open Subscription in the menu bar to see the plans, upgrade or restore a purchase. Purchases are handled by the App Store.

All devices are listed in the left sidebar.

• Add: click Add Device.
• Edit: click the pencil icon next to a device.
• Delete: right-click a device and choose Delete. This also removes its saved walk results and monitored OIDs.
• Search: use the field at the top of the sidebar.

For many devices, use a CSV file:

• Devices > Download CSV Template… saves a template with all columns.
• Fill in one device per row and choose Devices > Import Devices from CSV… (⇧⌘O).

A shared credential is a community string or an SNMPv3 user that you define once and use on many devices. Open it with the key button at the bottom of the sidebar, or choose Save as Shared Credential… in the device editor. When the password changes, edit the credential and every device using it picks it up. Shared credentials are a Pro feature.

Set the SNMP version of a device or credential to v3 to reveal the security fields:

• Security level: noAuthNoPriv (user name only), authNoPriv (authentication), authPriv (authentication and encryption).
• Authentication protocol: MD5, SHA or SHA-256.
• Privacy protocol: DES, AES or AES-256.
• Enter the user name and passwords exactly as configured on the device. Spaces and line breaks pasted at the end are ignored.

Credentials are stored locally in the app's sandbox container on your Mac and are only used to talk to your devices.

A walk retrieves every OID under a subtree.

• Select a device. Full Discovery walks everything from 1.3.6.1.
• To walk only part of the tree, click Select MIBs…, tick the MIBs you want and click Walk (Pro).
• Results stream in as they arrive. Stop a long walk at any time.
• Switch between table and tree view, filter with the search field, and toggle Numeric OIDs.
• Export CSV saves the results (Pro).

SNMP Explorer walks with GET-NEXT on SNMPv1 and GET-BULK on v2c and v3. The last walk of each device is kept, so it is still there after a relaunch.

Type an OID in the OID field and click Single Query to run one GET. Value and type appear in the same pane as walk results. Right-click any result and choose Add to Monitor to start polling it.

macOS includes the net-snmp command-line tools in /usr/bin, so you can compare what SNMP Explorer shows with a quick check in Terminal. snmpwalk uses GET-NEXT; snmpbulkwalk uses GET-BULK and is much faster on v2c and v3.

$ snmpwalk -v 2c -c public 192.0.2.10 1.3.6.1.2.1.1
SNMPv2-MIB::sysDescr.0 = STRING: …
SNMPv2-MIB::sysObjectID.0 = OID: …
DISMAN-EVENT-MIB::sysUpTimeInstance = Timeticks: (14967464) 1 day, 17:34:34.64
…
$ snmpbulkwalk -v 2c -c public -Cp 192.0.2.10
…
Variables found: 70

SNMPv3 uses a user instead of a community:

$ snmpwalk -v 3 -l authPriv -u admin -a SHA -A authpass -x AES -X privpass 192.0.2.10 1.3.6.1.2.1.1

The command-line tools only know the standard MIBs that ship with macOS, so vendor OIDs under 1.3.6.1.4.1 stay numeric. SNMP Explorer names them from its built-in descriptions and your imported MIBs.

Names and descriptions come from two sources: the built-in database of more than 600 OIDs, and the MIB files you import. Your imported MIBs take priority. If a MIB offers several descriptions for one OID, SNMP Explorer asks once which one to show.

Monitor is the first entry in the sidebar (Pro).

• Click Add OID, enter the OID and an optional name.
• Select one or several devices; each gets its own card.
• Choose the poll interval: 15 s, 30 s, 1 m, 5 m, 15 m, 30 m, 1 h, or a custom value.

You can also right-click a walk result and choose Add to Monitor.

Each card shows the current value, its type, the time of the last poll and a sparkline of up to 200 samples. Samples are kept in memory and start fresh after a relaunch.

• Live: the last poll succeeded.
• Stale: one poll was missed. The reason is shown on the card.
• Error: two polls in a row failed. Hover the status for details.

Polls to one device are sent one after another, which keeps small agents in UPS units, PDUs and RAID controllers from dropping requests.

Stop All and Start All control every card; the switch on a card controls just that one. Use the device menu at the top to show one device only.

1. In DSM 7, open Control Panel > Terminal & SNMP > SNMP, tick Enable SNMP service and either the SNMPv1, SNMPv2c service with a community, or the SNMPv3 service with a user and password. Click Apply.
2. Download the Synology MIB pack from Synology's MIB guide (Synology_MIB_File.zip, 21 text files).
3. In SNMP Explorer, click Add Device, enter the NAS address and the community or SNMPv3 user from DSM, then Test Connection.
4. Open MIBs > Manage MIBs…, click Import MIB File… and select all 21 files. Each module brings its own root, so none needs a parent MIB.
5. Click Select MIBs…, tick synoSystem, synoDisk and synoRaid in the Imported group, then Walk.
6. Right-click the rows you want and choose Add to Monitor. Each becomes a card polled every minute.

N is the row index the walk shows. systemStatus is 1 for normal and 2 for failed; diskHealthStatus 1 normal, 2 warning, 3 critical, 4 failing; raidStatus 1 normal, 11 degraded, 12 crashed (other values are running tasks such as repair or scrubbing). DSM does not send SNMP traps, so polling is the only way to watch the NAS. Steps 4 to 6 use Pro features.

SNMP Explorer receives SNMPv1 and v2c traps and acknowledges informs. It listens on UDP 1162, because apps from the Mac App Store are not allowed to open ports below 1024.

• Configure your devices to send traps to <IP of your Mac>:1162.
• Traps from a device appear in the drawer at the bottom of its pane. The Monitor view has a Trap Feed across all devices, which can be detached into its own window.
• Click the trap badge on a monitor card to filter the feed to that OID.
• Change the port in Preferences (⌘,).

Some devices cannot change the trap port. Redirect port 162 to 1162 on your Mac with a packet-filter rule. Preferences shows the command; it needs an administrator password and lasts until the next restart:

echo "rdr pass on lo0 inet proto udp from any to any port 162 -> 127.0.0.1 port 1162" | sudo pfctl -ef -

With SNMP Explorer running, send a test linkDown trap and an inform from Terminal on the same Mac:

$ snmptrap -v 2c -c public 127.0.0.1:1162 "" 1.3.6.1.6.3.1.1.5.3
$ snmpinform -v 2c -c public -r 0 -t 3 127.0.0.1:1162 "" 1.3.6.1.6.3.1.1.5.3

The trap appears in the drawer of the device whose host is 127.0.0.1, and in the Trap Feed. The inform returns at once, because SNMP Explorer acknowledges it; without a listener it fails after three seconds with Timeout. A trap sent to 127.0.0.1 does not test the macOS firewall, so also send one from another machine to <IP of your Mac>:1162.

Trap names come from these standard traps and from your imported MIBs. A trap that carries snmpTrapAddress.0 is shown under the device with that address rather than the sender's.

Vendor MIB files give vendor-specific OIDs readable names (Pro).

• Open MIBs > Manage MIBs… (⇧⌘M).
• Click Import MIB File… and choose the MIB files (.mib, .my, .txt).
• Files are copied into the app's own storage, so the originals can be moved or deleted. Reload parses them again.
• A single vendor MIB usually works without its parent MIB: the enterprise roots of common vendors are built in.

More than 600 OID descriptions are built in. The MIB picker groups them as Standard MIBs, Routing, HPE / ProLiant, Cisco, Juniper and Other Vendors. In the MIB Manager, the Built-in Presets tab lets you hide presets you never use.

An OID is the dotted path to one value. Everything under 1.3.6.1.2.1 is standard MIB-2; everything under 1.3.6.1.4.1 belongs to a vendor, numbered in the IANA Private Enterprise Numbers registry (9 is Cisco, 6574 is Synology).

• In SNMP Explorer, run Full Discovery and type a name or part of a description into the filter field. Untick Numeric OIDs to see names.
• For vendor objects, import the vendor MIB (MIBs > Manage MIBs…). Vendors publish their MIB files on their support sites, usually next to the firmware.
• The OID reference lists every OID SNMP Explorer knows out of the box.

In Terminal, snmptranslate converts between names and numbers and prints definitions:

$ snmptranslate -On SNMPv2-MIB::sysDescr.0
.1.3.6.1.2.1.1.1.0
$ snmptranslate 1.3.6.1.2.1.2.2.1.10
IF-MIB::ifInOctets
$ snmptranslate -TB 'ifHC.*Octets'
IF-MIB::ifHCOutOctets
IF-MIB::ifHCInOctets
$ snmptranslate -Td SNMPv2-MIB::sysDescr
$ snmptranslate -Tp IF-MIB::ifEntry

Scalars end in .0; table cells end in their row index. Common OIDs:

If queries or walks time out, check the following:

• Local network permission: System Settings > Privacy & Security > Local Network must allow SNMP Explorer.
• Firewall: UDP port 161 must be open between your Mac and the device.
• Community string: it is case-sensitive and must match the device.
• Access list: many devices only answer to listed manager addresses. Add your Mac's IP.
• SNMP service: make sure SNMP is enabled on the device.

Use Test Connection in the device editor to check quickly.

SNMP Explorer reports exactly what the device answered, and names the setting to check:

Spaces and line breaks pasted at the end of a user name or password are ignored, so a password copied with its trailing newline works.

• The device must send to port 1162, or you need the port 162 redirect.
• The macOS firewall must allow incoming connections for SNMP Explorer.
• The status line at the bottom right shows the port the app is listening on.

Can't find what you're looking for? We're happy to help.

• Email: info@toz.red
• Please include your macOS version, the SNMP Explorer version and a description of the problem. Help > Report an Issue… in the app collects the system details for you.
• We aim to respond within 1–2 business days.