As a full-stack developer and seasoned network engineer, I manage infrastructure for clients ranging from small offices to nationwide enterprises. To maintain high uptime and performance, having visibility into all devices is critical. For this, snmpwalk is an invaluable tool in my toolbox.
Unlike typical SNMP getter utilities, snmpwalk efficiently polls entire MIB trees to extract deep health statistics, performance metrics, and configurations from servers, switches, routers, printers and more. Its breadth, ease of use, and reliability make it my go-to for monitoring dynamic environments.
In this comprehensive guide, I‘ll demonstrate advanced snmpwalk usage for system admins and network engineers looking to level-up their network visibility.
SNMP and MIB Refresher
Before diving further into snmpwalk, let‘s refresh some core SNMP concepts.
SNMP is a UDP-based network management protocol for querying device data and altering configurations. Agents expose virtual data stores called MIBs (Management Information Bases) with hierarchal object IDs that map to system metrics.
Manager software leverages operations like GET, GETNEXT, and SET to retrieve and change these objects. Some common MIB branches are:
- SYSTEM – OS, services, contacts, usernames, etc.
- INTERFACES – Network interface statuses and traffic counters
- IP – Protocol stats and routing tables
- IF-MIB – Additional interface utilization details
And many vendors define custom branches for their systems.
Now let‘s see how we can leverage snmpwalk to tap into this goldmine!
Advantages of Snmpwalk vs Other Protocols
While typical SNMP manager tools focus on polling single OID values, snmpwalk efficiently walks all entries under a specified MIB branch. This provides complete device details in a single request – invaluable for quick discovery and troubleshooting.
In contrast to higher layer monitoring suites, SNMP requires less overhead and provides universal device support. Implementations exist across operating systems, network hardware, printers, sensors, and other systems.
Finally, unlike SSH/CLI, SNMP management is out-of-band allowing remote querying even during device OS failures.
Now that we‘ve covered the basics, let‘s walk through installation.
Installing Snmpwalk in Linux Environments
Since snmpwalk is bundled with Net-SNMP, installation is straightforward on most distributions:
Debian/Ubuntu
sudo apt install snmpRHEL/CentOS
sudo yum install net-snmp-utilsFedora
sudo dnf install net-snmp-utilsVerify with:
snmpwalkWith the powerful walk engine installed, we‘re ready to start querying!
Walking System MIBs for OS and Hardware Inventory
My first use of snmpwalk is often creating infrastructure inventory reports – vital for managing dynamic environments.
I can poll sysDescr, sysObjectID, sysName, sysLocation, and sysContact from Linux machines, network gear like firewalls and switches, printers, and more. This reveals device types, versions, locations, purposes, and responsible teams across the estate.
For example, to generate an inventory on my network‘s public subnet:
snmpwalk -v2c -c public 10.1.2.0/24 sysDescr sysObjectID sysName sysLocationBy grepping through outputs, I can classify and report on various device types across subnets and sites. If standardized properly, automating inventory documentation becomes trivial with snmpwalk polling.
Monitoring Wireless Infrastructure Health
While wired performance monitoring gets more attention, keeping wireless infrastructure tuned is equally as important in modern environments.
By polling Wi-Fi controller and access point MIBs, snmpwalk makes this easy. On Aruba controllers, we can view client counts, types, statuses, channel utilization, and more.
snmpwalk -v2c -c public 192.168.200.10 .1.3.6.1.4.1.14823.2.3.3For Ruckus ZoneDirector controllers:
snmpwalk -v2c -c public 192.168.200.20 1.3.6.1.4.1.25053.1.2.1.1.1.15.30.1.1.3This exposes associated devices so we can watch client growth and identify possible RF saturation issues.
Access point-level metrics are also available. Here‘s signal-to-noise ratio, traffic levels, and channel utilization metrics for troubleshooting connectivity complaints:
snmpwalk -v2c -c ap123 192.168.200.101 \
.1.3.6.1.4.1.388.11.2.4.1.4.1.0 | grep snr.*\ | sort -n
.1.3.6.1.4.1.388.11.2.4.1.5.1.0
.1.3.6.1.4.1.388.11.2.4.1.9.1.0As wireless replaces wired, properly monitoring spectrum environments becomes essential.
Integration with Monitoring and Analysis Systems
While snmpwalk provides raw metric outputs, I get further value sending results into analytic suites like Grafana, InfluxDB, and ELK Stack.
I‘ve created scripts that poll metrics then transform and load as JSON into various databases. This allows great flexibility visualizing trends, defining alerts, and correlating data.
For example, by collecting and analyzing interface counter errors over time, I can detect intermittent Layer 1 problems that spike inconsistently. Rate vs error graphs help pinpoint such difficult issues.
I also generate usage reports on printer toner, power consumption, cooling efficiency, and rack space which drive budget and planning discussions with management.
The possibilities are endless when combining snmpwalk with analytic and monitoring platforms!
Querying Router QoS Statistics and Performance
While server monitoring gets most attention, I can‘t stress enough the importance of surveying network device health – the glue binding infrastructure.
On routers and switches, interface errors, discards, and layer 3 drops indicate problems affecting application performance. Bottlenecks manifest as excessive queue drops or high buffer utilization.
Here are some typical metrics I poll:
snmpwalk -v2 -c cisco 192.168.100.1 ifInErrors ifInDiscards ifOutErrors ifOutDiscards | sort -g
snmpwalk -v2c -c cisco 192.168.100.1 \
CISCO-CLASS-BASED-QOS-MIB::cbQosCMDropByte64 \
CISCO-CLASS-BASED-QOS-MIB::cbQosCMPrePolicyByte64The first exposes physical layer issues on device interfaces which should be zero at layer 3.
The second reveals QoS byte drops pre and post routing policy application – helping locate oversubscription.
Trending this data has helped me identify and resolve problems before users notice degraded application performance.
Fine-Tuning Network Devices with Snmpset
While not as popular, snmpwalk‘s SET cousin allows altering device configurations. This reduces reliance on fragile terminal emulations when pushing mass changes.
Some examples where I leverage snmpset:
1. Updating switchport details:
snmpset -v2c -c cisco 192.168.200.47 \
IF-MIB::ifAdminStatus.47 = 2 \
IF-MIB::ifAlias.47 = ‘Finance Printer 5‘ 2. Creating static DHCP bindings:
snmpset -v2c -c dhcpmgr 192.168.100.10 \
UDP-MIB::udplocalAddress.9.114.101.98 = 182855490This binds MAC 18:28:55:49:01:98 to x.x.x.114
While many shy from SET, I‘ve found it reliable for performing repetitive tasks at scale.
Discovering Network Devices Physically with CDP or LLDP
Troubleshooting connectivity problems requires understanding Layer 1 and 2 topologies. Typically this mapping was manual — but with snmpwalk scanning CDP or LLDP tables, I can dynamically trace interswitch physical links and layout.
On Cisco kit polling CDP:
snmpwalk -v2c -c cisco 10.1.1.1 \
CISCO-CDP-MIB::cdpCacheDeviceId
CISCO-CDP-MIB::cdpCacheDevicePortFor Juniper kit using LLDP:
snmpwalk -v2c -c lldp 10.1.1.1 \
LLDP-MIB::lldpLocSysDesc
LLDP-MIB::lldpRemSysDesc
LLDP-MIB::lldpRemSysCapEnabledThis exposes connected devices and interfaces bridging our target switch, allowing rapid tracing of port statuses and physical connectivity.
Automating Campus Network Discovery with Snmpwalk
I occasionally need to document and analyze device layouts across large campuses with 100s of closets and 10,000s of ports. While mapping these manually takes weeks, I built a custom snmpwalk-based discovery script that provides initial drafting in hours.
It first polls ARP tables to locate L3 switch IPs then scans device interfaces using IF-MIB ifDescr and ifAlias. This reveals uplink trunk ports and downstream switch connections.
Layer 2 topology stitching occurs by traversing CDP tables as covered previously. Some pseudocode:
# Locate L3 switch IPs from gateway ARPs
for subnet in networks:
arpwalk gateways
# Walk ifDescr and ifAlias
for switch in switches:
snmpwalk interfaces
# Trace physical links
for switch in switches:
snmpwalk CDP
# Draw topology mapWhile the maps require some manual correction, this automatic drafting saved countless days across large engagements.
This demonstrates the power of snmpwalk for simplifying large bureaucracies.
Considerations When Using Snmpwalk
While snmpwalk has become a vital tool for me, it does have some key considerations:
- Network equipment must have SNMP enabled and accessible
- Firewalls require holes allowing SNMP traffic
- Access lists should lock down snmpwalk sources
- Differences between SNMP v1, v2c and v3 authentication should be understood
- Consideration for community strings or v3 cred management
- Traps from agents indicate problems but can overwhelm collectors
Additionally, while SNMP standardization helps, some devices utilize proprietary MIBs requiring research before effectively polling metrics.
Finally, organizations should carefully consider access controls to ensure sensitive data isn‘t exposed.
Now that we‘ve covered considerations, let‘s wrap this up!
Conclusion
As evident, snmpwalk is an incredibly versatile, efficient, and valuable tool for managing dynamic network environments and hardware. Its ability to poll entire MIB branches facilitates rapid discovery, troubleshooting, and monitoring for admins.
I hope this guide has inspired you to utilize snmpwalk more actively across your infrastructure. If I had to pick only one SNMP tool to keep as a network engineer, it would undoubtedly be snmpwalk.
As demonstrated, it can extract invaluable details inaccessible otherwise across the majority of organization equipment with minimal overhead.
Let me know if you have any other creative applications of snmpwalk or feedback on the tool!