How to monitor ESXi host hardware with SNMP
The Simple Network Management Protocol (SNMP) is a protocol for monitoring and configuration of network-attached devices. SNMP exposes data in the form of variables and values. These variables can then be queried or set. A query retrieves the value of a variable, a set operation assigns a value to a variable. The variables are organized in a hierarchy and each variable is identified by an object identifiers (OID). The management information base (MIB ) describes this hierarchy. MIB files (simple text files) contain metadata for each OID. These are necessary for the translation of a numeric OID into a human-readable format. SNMP knows two devices types:
- the managed device which runs the SNMP agent
- the network management station (NMS) which runs the management software
The NMS queries the SNMP agent with GET requests. Configuration changes are made using SET requests. The SNMP agent can inform the NMS about state changes using a SNMP trap message. The easiest way for authentication is the SNMP community string.
SNMP is pretty handy and it’s still used, especially for monitoring and managing networking components. SNMP has the benefit, that it’s very lightweight. Monitoring a system with WBEM or using an API can cause slightly more load, compared to SNMP. Furthermore, SNMP is a internet-protocol standard. Nearly every device supports SNMP.
Monitoring host hardware with SNMP
Why should I monitor my ESXi host hardware with SNMP? The vCenter Server can trigger an alarm and most customers use applications like VMware vRealize Operations, Microsoft System Center Operations Manager, or HPE Systems Insight Manager (SIM). There are better ways to monitor the overall health of an ESXi host. But sometimes you want to get some stats about the network interfaces (throughput), or you have a script that should do something, if a NIC goes down or something else happens. Again, SNMP is very resource-friendly and widely supported.
Configure SNMP on ESXi
I focus on ESXi 5.1 and beyond. The ESXi host is called “the SNMP Agent”. We don’t configure traps or trap destinations. We just want to poll the SNMP agent using SNMP GET requests. The configuration is done using esxcli . First of all, we need to set a community string and enable SNMP.
[root@esx1:~] esxcli system snmp set -c public -e true
[root@esx1:~] esxcli system snmp get
Authentication:
Communities: public
Enable: true
Engineid: 00000063000000a100000000
Hwsrc: indications
Largestorage: true
Loglevel: info
Notraps:
Port: 161
Privacy:
Remoteusers:
Syscontact:
Syslocation:
Targets:
Users:
V3targets:
That’s it! The necessary firewall ports and services are opened and started automatically.
Querying the SNMP agent
I use a CentOS VM to show you some queries. The Net-SNMP package contains the tools snmpwalk and snmpget. To install the Net-SNMP utils, simply use yum .
[root@web ~]# yum install net-snmp-utils.x86_64
Download the VMware SNMP MIB files, extract the ZIP file, and copy the content to to /usr/share/snmp/mibs.
[root@web mibs]# ls -lt
total 3852
-rw-r--r--. 1 root root 50968 Jun 3 17:05 BRIDGE-MIB.mib
-rw-r--r--. 1 root root 59268 Jun 3 17:05 ENTITY-MIB.mib
-rw-r--r--. 1 root root 52586 Jun 3 17:05 HOST-RESOURCES-MIB.mib
-rw-r--r--. 1 root root 10583 Jun 3 17:05 HOST-RESOURCES-TYPES.mib
-rw-r--r--. 1 root root 7309 Jun 3 17:05 IANA-ADDRESS-FAMILY-NUMBERS-MIB.mib
-rw-r--r--. 1 root root 33324 Jun 3 17:05 IANAifType-MIB.mib
-rw-r--r--. 1 root root 3890 Jun 3 17:05 IANA-RTPROTO-MIB.mib
-rw-r--r--. 1 root root 76268 Jun 3 17:05 IEEE8021-BRIDGE-MIB.mib
-rw-r--r--. 1 root root 89275 Jun 3 17:05 IEEE8021-Q-BRIDGE-MIB.mib
-rw-r--r--. 1 root root 16082 Jun 3 17:05 IEEE8021-TC-MIB.mib
-rw-r--r--. 1 root root 44543 Jun 3 17:05 IEEE8023-LAG-MIB.mib
-rw-r--r--. 1 root root 71747 Jun 3 17:05 IF-MIB.mib
-rw-r--r--. 1 root root 16782 Jun 3 17:05 INET-ADDRESS-MIB.mib
-rw-r--r--. 1 root root 46405 Jun 3 17:05 IP-FORWARD-MIB.mib
-rw-r--r--. 1 root root 185967 Jun 3 17:05 IP-MIB.mib
-rw-r--r--. 1 root root 229 Jun 3 17:05 list-ids-diagnostics.txt
-rw-r--r--. 1 root root 77406 Jun 3 17:05 LLDP-V2-MIB.mib
-rw-r--r--. 1 root root 16108 Jun 3 17:05 LLDP-V2-TC-MIB.mib
-rw-r--r--. 1 root root 23777 Jun 3 17:05 notifications.txt
-rw-r--r--. 1 root root 39918 Jun 3 17:05 P-BRIDGE-MIB.mib
-rw-r--r--. 1 root root 84172 Jun 3 17:05 Q-BRIDGE-MIB.mib
-rw-r--r--. 1 root root 1465 Jun 3 17:05 README
-rw-r--r--. 1 root root 223872 Jun 3 17:05 RMON2-MIB.mib
-rw-r--r--. 1 root root 148032 Jun 3 17:05 RMON-MIB.mib
-rw-r--r--. 1 root root 22342 Jun 3 17:05 SNMP-FRAMEWORK-MIB.mib
-rw-r--r--. 1 root root 5543 Jun 3 17:05 SNMP-MPD-MIB.mib
-rw-r--r--. 1 root root 8259 Jun 3 17:05 SNMPv2-CONF.mib
-rw-r--r--. 1 root root 31588 Jun 3 17:05 SNMPv2-MIB.mib
-rw-r--r--. 1 root root 8932 Jun 3 17:05 SNMPv2-SMI.mib
-rw-r--r--. 1 root root 38048 Jun 3 17:05 SNMPv2-TC.mib
-rw-r--r--. 1 root root 28647 Jun 3 17:05 TCP-MIB.mib
-rw-r--r--. 1 root root 93608 Jun 3 17:05 TOKEN-RING-RMON-MIB.mib
-rw-r--r--. 1 root root 20951 Jun 3 17:05 UDP-MIB.mib
-rw-r--r--. 1 root root 3175 Jun 3 17:05 UUID-TC-MIB.mib
-rw-r--r--. 1 root root 2326 Jun 3 17:05 VMWARE-CIMOM-MIB.mib
-rw-r--r--. 1 root root 22411 Jun 3 17:05 VMWARE-ENV-MIB.mib
-rw-r--r--. 1 root root 53480 Jun 3 17:05 VMWARE-ESX-AGENTCAP-MIB.mib
-rw-r--r--. 1 root root 2328 Jun 3 17:05 VMWARE-HEARTBEAT-MIB.mib
-rw-r--r--. 1 root root 1699 Jun 3 17:05 VMWARE-NSX-MANAGER-AGENTCAP-MIB.mib
-rw-r--r--. 1 root root 146953 Jun 3 17:05 VMWARE-NSX-MANAGER-MIB.mib
-rw-r--r--. 1 root root 15641 Jun 3 17:05 VMWARE-OBSOLETE-MIB.mib
-rw-r--r--. 1 root root 2173 Jun 3 17:05 VMWARE-PRODUCTS-MIB.mib
-rw-r--r--. 1 root root 8305 Jun 3 17:05 VMWARE-RESOURCES-MIB.mib
-rw-r--r--. 1 root root 3736 Jun 3 17:05 VMWARE-ROOT-MIB.mib
-rw-r--r--. 1 root root 11142 Jun 3 17:05 VMWARE-SRM-EVENT-MIB.mib
-rw-r--r--. 1 root root 3872 Jun 3 17:05 VMWARE-SYSTEM-MIB.mib
-rw-r--r--. 1 root root 7017 Jun 3 17:05 VMWARE-TC-MIB.mib
-rw-r--r--. 1 root root 7611 Jun 3 17:05 VMWARE-VA-AGENTCAP-MIB.mib
-rw-r--r--. 1 root root 8777 Jun 3 17:05 VMWARE-VC-EVENT-MIB.mib
-rw-r--r--. 1 root root 38576 Jun 3 17:05 VMWARE-VCOPS-EVENT-MIB.mib
-rw-r--r--. 1 root root 26952 Jun 3 17:05 VMWARE-VMINFO-MIB.mib
Now we can use snmpwalk to “walk down the hierarchy “. This is only a small part of the complete output. The complete snmpwalk output has more than 4000 lines!
[root@web mibs]# snmpwalk -m ALL -c public -v 2c esx1.lab.local
SNMPv2-MIB::sysDescr.0 = STRING: VMware ESXi 6.0.0 build-3825889 VMware, Inc. x86_64
SNMPv2-MIB::sysObjectID.0 = OID: VMWARE-PRODUCTS-MIB::vmwESX
DISMAN-EVENT-MIB::sysUpTimeInstance = Timeticks: (402700) 1:07:07.00
SNMPv2-MIB::sysContact.0 = STRING:
SNMPv2-MIB::sysName.0 = STRING: esx1
Now we can search for interesting parts. If you want to monitor the link status of the NICs, try this:
[root@web mibs]# snmpwalk -m ALL -c public -v 2c esx1.lab.local IF-MIB::ifDescr
IF-MIB::ifDescr.1 = STRING: Device vmnic0 at 03:00.0 bnx2
IF-MIB::ifDescr.2 = STRING: Device vmnic1 at 03:00.1 bnx2
IF-MIB::ifDescr.3 = STRING: Device vmnic2 at 04:00.0 bnx2
IF-MIB::ifDescr.4 = STRING: Device vmnic3 at 04:00.1 bnx2
IF-MIB::ifDescr.5 = STRING: Device vmnic4 at 06:00.0 bnx2
IF-MIB::ifDescr.6 = STRING: Device vmnic5 at 06:00.1 bnx2
IF-MIB::ifDescr.7 = STRING: Distributed Virtual VMware switch: DvsPortset-0
IF-MIB::ifDescr.8 = STRING: Virtual interface: vmk0 on port 33554442 DVS 6b a0 37 50 c6 24 04 b8-25 08 f5 ea 32 ef 48 27
IF-MIB::ifDescr.9 = STRING: Virtual interface: vmk1 on port 33554443 DVS 6b a0 37 50 c6 24 04 b8-25 08 f5 ea 32 ef 48 27
IF-MIB::ifDescr.10 = STRING: Virtual interface: vmk2 on port 33554444 DVS 6b a0 37 50 c6 24 04 b8-25 08 f5 ea 32 ef 48 27
IF-MIB::ifDescr.11 = STRING: Virtual interface: vmk3 on port 33554445 DVS 6b a0 37 50 c6 24 04 b8-25 08 f5 ea 32 ef 48 27
As you can see, I used a subtree of the whole hierarchy (IF-MIB::ifDescr). This is the “translated” OID. To get the numeric OID, you have to add the option -O fn to snmpwalk .
[root@web mibs]# snmpwalk -O fn -m ALL -c public -v 2c esx1.lab.local IF-MIB::ifDescr
.1.3.6.1.2.1.2.2.1.2.1 = STRING: Device vmnic0 at 03:00.0 bnx2
.1.3.6.1.2.1.2.2.1.2.2 = STRING: Device vmnic1 at 03:00.1 bnx2
.1.3.6.1.2.1.2.2.1.2.3 = STRING: Device vmnic2 at 04:00.0 bnx2
.1.3.6.1.2.1.2.2.1.2.4 = STRING: Device vmnic3 at 04:00.1 bnx2
.1.3.6.1.2.1.2.2.1.2.5 = STRING: Device vmnic4 at 06:00.0 bnx2
.1.3.6.1.2.1.2.2.1.2.6 = STRING: Device vmnic5 at 06:00.1 bnx2
.1.3.6.1.2.1.2.2.1.2.7 = STRING: Distributed Virtual VMware switch: DvsPortset-0
.1.3.6.1.2.1.2.2.1.2.8 = STRING: Virtual interface: vmk0 on port 33554442 DVS 6b a0 37 50 c6 24 04 b8-25 08 f5 ea 32 ef 48 27
.1.3.6.1.2.1.2.2.1.2.9 = STRING: Virtual interface: vmk1 on port 33554443 DVS 6b a0 37 50 c6 24 04 b8-25 08 f5 ea 32 ef 48 27
.1.3.6.1.2.1.2.2.1.2.10 = STRING: Virtual interface: vmk2 on port 33554444 DVS 6b a0 37 50 c6 24 04 b8-25 08 f5 ea 32 ef 48 27
.1.3.6.1.2.1.2.2.1.2.11 = STRING: Virtual interface: vmk3 on port 33554445 DVS 6b a0 37 50 c6 24 04 b8-25 08 f5 ea 32 ef 48 27
You can use snmptranslate to translate an OID.
[root@web mibs]# snmptranslate .1.3.6.1.2.1.2.2.1.2
IF-MIB::ifDescr
[root@web mibs]# snmptranslate -O fn IF-MIB::ifDescr
.1.3.6.1.2.1.2.2.1.2
So far, we have only the description of the interfaces. With a little searching, we find the status of the interfaces (I stripped the output).
IF-MIB::ifOperStatus.1 = INTEGER: up(1)
IF-MIB::ifOperStatus.2 = INTEGER: up(1)
IF-MIB::ifOperStatus.3 = INTEGER: down(2)
IF-MIB::ifOperStatus.4 = INTEGER: down(2)
IF-MIB::ifOperStatus.5 = INTEGER: up(1)
IF-MIB::ifOperStatus.6 = INTEGER: up(1)
ifOperStatus.1 corresponds with ifDescr.1 , ifOperStatus.2 corresponds with ifDescr.2 and so on. The ifOperStatus corresponds with the status of the NICs in the vSphere Web Client.
Patrick Terlisten/ vcloudnine.de/ Creative Commons CC0
If you want to monitor the fans or power supplies, use these these OIDs.
HOST-RESOURCES-MIB::hrDeviceDescr.35 = STRING: POWER Power Supply 1
HOST-RESOURCES-MIB::hrDeviceDescr.36 = STRING: POWER Power Supply 2
HOST-RESOURCES-MIB::hrDeviceDescr.37 = STRING: FAN Fan Block 1
HOST-RESOURCES-MIB::hrDeviceDescr.38 = STRING: FAN Fan Block 2
HOST-RESOURCES-MIB::hrDeviceDescr.39 = STRING: FAN Fan Block 3
HOST-RESOURCES-MIB::hrDeviceDescr.40 = STRING: FAN Fan Block 4
HOST-RESOURCES-MIB::hrDeviceStatus.35 = INTEGER: running(2)
HOST-RESOURCES-MIB::hrDeviceStatus.36 = INTEGER: running(2)
HOST-RESOURCES-MIB::hrDeviceStatus.37 = INTEGER: running(2)
HOST-RESOURCES-MIB::hrDeviceStatus.38 = INTEGER: running(2)
HOST-RESOURCES-MIB::hrDeviceStatus.39 = INTEGER: running(2)
HOST-RESOURCES-MIB::hrDeviceStatus.40 = INTEGER: running(2)
Many possibilities
SNMP offers a simple and lightweight way to monitor a managed device. It’s not a replacement for vCenter, vROps or SCOM. But it can be an addition, especially because SNMP is an internet-protocol standard.