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SNMP Monitoring

Cumulus RMP utilizes the open source Net-SNMP agent snmpd, v5.7.3, which provides support for most of the common industry-wide MIBs, including interface counters and TCP/UDP IP stack data.

Cumulus RMP does not prevent customers from extending SNMP features. However, Cumulus Networks encourages the use of higher performance monitoring environments, rather than SNMP.

Introduction to SNMP (Simple Network Management Protocol)

SNMP is an IETF standards-based network management architecture and protocol that traces its roots back to Carnegie-Mellon University in 1982. Since then, it’s been modified by programmers at the University of California. In 1995, this code was also made publicly available as the UCD project. After that, ucd-snmp was extended by work done at the University of Liverpool as well as later in Denmark. In late 2000, the project name changed to net-snmp and became a fully-fledged collaborative open source project. The version used by Cumulus Networks is base on the latest net-snmp 5.7.3 branch with added custom MIBs and pass through and pass persist scripts.

Configuring Ports for SNMP to Listen for Requests

For security reasons, the default port binding for snmpd is the loopback local address; consequently by default, the SNMP service does not listen for SNMP requests from outside the switch. In order to listen to requests from outside the switch, you need to change this binding to a specific IP address (or all interfaces) after configuring security access (community strings, users, and so forth). This is a change from older versions of Cumulus RMP (before version 3.0), which listened to incoming requests on all interfaces by default. The snmpd configuration file is /etc/snmp/snmpd.conf and should be modified before enabling and starting snmpd. The default configuration has no access community strings defined so snmpd will not respond to any SNMP requests until this is added.

Starting the SNMP Daemon

The following procedure is the recommended process to start snmpd and monitor it using systemctl.

To start the SNMP daemon:

  1. Start the snmpd daemon:

    cumulus@switch:~$ sudo systemctl start snmpd.service
  2. Configure the snmpd daemon to start automatically after reboot:

    cumulus@switch:~$ sudo systemctl enable snmpd.service
  3. To enable snmpd to restart automatically after failure:

    1. Create a file called /etc/systemd/system/snmpd.service.d/restart.conf.

    2. Add the following lines:

    3. Run systemctl daemon-reload.

Once the service is started, SNMP can be used to manage various components on the Cumulus RMP switch.

Configuring SNMP

Cumulus RMP ships with a production usable default snmpd.conf file included. This section covers a few basic configuration options in snmpd.conf. For more information regarding further configuring this file, refer to the snmpd.conf man page.

The default snmpd.conf file does not include all supported MIBs or OIDs that can be exposed.

Customers must at least change the default community string for v1 or v2c environments or the snmpd daemon will not respond to any requests.

Setting up the Custom Cumulus Networks MIBs

No changes are required in the /etc/snmp/snmpd.conf file on the switch, in order to support the custom Cumulus Networks MIBs. The following lines are already included by default:

view systemonly included .
view systemonly included .
pass_persist . /usr/share/snmp/
pass_persist . /usr/share/snmp/

However, several files need to be copied to the server, in order for the custom Cumulus MIB to be recognized on the destination NMS server.

  • /usr/share/snmp/Cumulus-Snmp-MIB.txt

  • /usr/share/snmp/Cumulus-Counters-MIB.txt

  • /usr/share/snmp/Cumulus-Resource-Query-MIB.txt

Enabling the . Range

Some MIBs, including storage information, are not included by default in snmpd.conf in Cumulus RMP. This results in some default views on common network tools (like librenms) to return less than optimal data. More MIBs can be included, by enabling all the . range. This simplifies the configuration file, removing concern that any required MIBs will be missed by the monitoring system. Various new MIBs were added for 3.0 and include the following: ENTITY and ENTITY-SENSOR MIB and parts of the BRIDGE-MIB and Q-BRIDGE-MIBs. These are included in the default configuration (Note: the view of the BRIDGE-MIB and Q-BRIDGE-MIB are commented out).

This configuration grants access to a large number of MIBs, including all MIB2 MIBs, which could reveal more data than expected. In addition to being a security vulnerability, it could consume more CPU resources.

To enable the . range:

  1. Open /etc/snmp/snmpd.conf in a text editor.

  2. Make sure the following lines are included in the configuration:

    # system
    view   systemonly  included   .
    # lldpd (Note: lldpd must be restarted with the -x option
    #     configured in order to send info to snmpd via Agent X
    view   systemonly  included   .1.0.8802.1.1.2
    # Cumulus specific
    view   systemonly  included   .
    view   systemonly  included   .
  3. Restart snmpd:

    # sudo systemctl start snmpd.service

Enabling Public Community

The snmpd authentication for versions 1 and 2 is disabled by default in Cumulus RMP. This password (called a community string) can be enabled by setting rocommunity (for read-only access) or rwcommunity (for read-write acces). To enable read-only querying by a client:

  1. Open /etc/snmp/snmpd.conf in a text editor.

  2. To allow read-only access using a password public from any client IP address (default) for the view you defined before with systemonly, add the following line to the end of the file, then save it:

    rocommunity public default -V systemonly
  3. Restart snmpd:

    cumulus@switch:~$ sudo systemctl restart snmpd.service

Configuring SNMPv3

Since community strings in versions 1 and 2c are sent in the clear, SNMPv3 is often used to enable authentication and encryption. SNMPv3 was first release around 2000. A minimal example is shown here for /etc/snmp/snmpd.conf that defines three users, each with a different combination of authentication and encryption. Please change these usernames and passwords before using this in a network:

Make sure you change the usernames and passwords in the sample code below, as the ones used here are for explanatory purposes only.

# simple no auth user
createUser user1
# user with MD5 authentication
createUser user2 MD5 user2password
# user with MD5 for auth and DES for encryption 
createUser user3 MD5 user3password DES user3encryption
# user999 with MD5 for authentication and DES for encryption
createUser user666 SHA user666password AES user666encryption
createUser user999 MD5 user999password DES user999encryption

# restrict users to certain OIDs
# (Note: creating rouser or rwuser will give
# access regardless of the createUser command above. However,
# createUser without rouser or rwuser will not provide any access).
rouser user1 noauth
rouser user2 auth
rwuser user3 priv
rwuser user666
rwuser user999

Once you make this configuration and restart the snmpd daemon, the user access can be checked with a client - the Debian package called snmp contains snmpget and snmpwalk, as well as other programs that are useful for checking daemon functionality from the switch itself or from another workstation. The following commands check the access for each user defined above from the localhost (the switch itself):

# check user1 which has no authentication or encryption (NoauthNoPriv)
snmpget -v 3 -u user1 -l NoauthNoPriv localhost
snmpwalk -v 3 -u user1 -l NoauthNoPriv localhost

# check user2 which has authentication but no encryption (authNoPriv)
snmpget -v 3 -u user2 -l authNoPriv -a MD5 -A user2password localhost
snmpget -v 3 -u user2 -l authNoPriv -a MD5 -A user2password localhost
snmpwalk -v 3 -u user2 -l authNoPriv -a MD5 -A user2password localhost
# check user3 which has both authentication and encryption (authPriv)
snmpget -v 3 -u user3 -l authPriv -a MD5 -A user3password -x DES -X user3encryption localhost .
snmpwalk -v 3 -u user3 -l authPriv -a MD5 -A user3password -x DES -X user3encryption localhost .

snmpwalk -v 3 -u user666 -l authPriv -a SHA -x AES -A user666password -X user666encryption localhost
snmpwalk -v 3 -u user999 -l authPriv -a MD5 -x DES -A user999password -X user999encryption localhost

A slightly more secure method of configuring SNMPv3 users without creating cleartext passwords is the following:

  1. Install the net-snmp-config script that is in libsnmp-dev package:

    cumulus@switch:~$ sudo apt-get update
    cumulus@switch:~$ sudo apt-get install libsnmp-dev
  2. Stop the daemon:

    cumulus@switch:~$ sudo systemctl stop snmpd
  3. Use the net-snmp-config command to create two users, one with MD5 and DES, and the next with SHA and AES.

    The minimum password length is 8 characters and the arguments `-a`
    and `-x` to `net-snmp-config` have different meanings than they do
    for `snmpwalk`.

    cumulus@switch:~$ sudo net-snmp-config --create-snmpv3-user -a md5authpass -x desprivpass -A MD5 -X DES userMD5withDES 
    cumulus@switch:~$ sudo net-snmp-config --create-snmpv3-user -a shaauthpass -x aesprivpass -A SHA -X AES userSHAwithAES
    cumulus@switch:~$ sudo systemctl start snmpd

This adds a createUser command in /var/lib/snmp/snmpd.conf. Do not edit this file by hand, unless you are removing usernames. It also adds the rwuser in /usr/share/snmp/snmpd.conf. You may want to edit this file and restrict access to certain parts of the MIB by adding noauth, auth or priv to allow unauthenticated access, require authentication or to enforce use of encryption, respectively.

The snmpd daemon reads the information from the /var/llib/snmp/snpmd.conf file and then the line is removed (eliminating the storage of the master password for that user) and replaced with the key that is derived from it (using the EngineID). This key is a localized key, so that if it is stolen it cannot be used to access other agents. To remove the two users userMD5withDES and userSHAwithAES, you need simply stop the snmpd daemon and edit the files /var/lib/snmp/snmpd.conf and /usr/share/snmp/snmpd.conf. Simply remove the lines containing the username. Then restart the snmpd daemon as in step 3 above.

From a client, you would access the MIB with the correct credentials. (Again, note that the roles of -x, -a and -X and -A are reversed on the client side as compared with the net-snmp-config command used above.)

snmpwalk -v 3 -u userMD5withDES -l authPriv -a MD5 -x DES -A md5authpass -X desprivpass localhost
snmpwalk -v 3 -u userSHAwithAES -l authPriv -a SHA -x AES -A shaauthpass -X aesprivpass localhost

Configuring Nutanix Prism

Nutanix Prism is a graphical user interface (GUI) for managing infrastructures and virtual environments.

Cumulus RMP Configuration

  1. SSH to the Cumulus RMP switch that needs to be configured, replacing [switch] below as appropriate:

    cumulus@workbench:~$ ssh cumulus@[switch]
  2. Confirm the switch is running Cumulus RMP 2.5.5 or newer:

    cumulus@switch$ cat /etc/lsb-release
    DISTRIB_ID="Cumulus RMP"
  3. Open the /etc/snmp/snmpd.conf file in an editor.

  4. Uncomment the following 3 lines in the /etc/snmp/snmpd.conf file, and save the file:


      pass_persist . /usr/share/snmp/
    • Community

      rocommunity public  default    -V systemonly
    • Line directly below the Q-BRIDGE-MIB (.

      # BRIDGE-MIB and Q-BRIDGE-MIB tables
      view   systemonly  included   .
  5. Restart snmpd:

    cumulus@switch$ sudo systemctl restart snmpd.service
    Restarting network management services: snmpd.

Nutanix Configuration

  1. Log into the Nutanix Prism. Nutanix defaults to the Home menu, referred to as the Dashboard:

  2. Click on the gear icon


    in the top right corner of the dashboard, and select NetworkSwitch:

  3. Click the +Add Switch Configuration button in the Network Switch Configuration pop up window.

  4. Fill out the Network Switch Configuration for the Top of Rack (ToR) switch configured for snmpd in the previous section:

    Configuration ParameterDescriptionValue Used in Example
    Switch Management IP AddressThis can be any IP address on the box. In the screenshot above, the eth0 management IP is used.
    Host IP Addresses or Host NamesIP addresses of Nutanix hosts connected to that particular ToR switch.,,,
    SNMP ProfileSaved profiles, for easy configuration when hooking up to multiple switches.None
    SNMP VersionSNMP v2c or SNMP v3. Cumulus RMP has only been tested with SNMP v2c for Nutanix integration.SNMP v2c
    SNMP Community NameSNMP v2c uses communities to share MIBs. The default community for snmpd is ‘public’.public

    The rest of the values were not touched for this demonstration. They
    are usually used with SNMP v3.

  5. Save the configuration. The switch will now be present in the Network Switch Configuration menu now.

  6. Close the pop up window to return to the dashboard.

  7. Open the Hardware option from the Home dropdown menu:

  8. Click the Table button.

  9. Click the Switch button. Configured switches are shown in the table, as indicated in the screenshot below, and can be selected in order to view interface statistics:


The switch has been added correctly, when interfaces hooked up to the Nutanix hosts are visible.

Switch Information Displayed on Nutanix Prism

  • Physical Interface (e.g. swp1, swp2). This will only display swp interfaces connected to Nutanix hosts by default.

  • Switch ID - Unique identifier that Nutanix keeps track of each port ID (see below)

  • Index - interface index, in the above demonstration swp49 maps to Index 52 because there is a loopback and two ethernet interface before the swp starts.

  • MTU of interface

  • MAC Address of Interface

  • Unicast RX Packets (Received)

  • Unicast TX Packets (Transmitted)

  • Error RX Packets (Received)

  • Error TX Packets (Transmitted)

  • Discard RX Packets (Received)

  • Discard TX Packets (Transmitted)

The Nutanix appliance will use Switch IDs that can also be viewed on the Prism CLI (by SSHing to the box). To view information from the Nutanix CLI, login using the default username nutanix, and the password nutanix/4u.

nutanix@NTNX-14SM15270093-D-CVM:$ ncli network list-switch
    Switch ID                 : 00051a76-f711-89b6-0000-000000003bac::5f13678e-6ffd-4b33-912f-f1aa6e8da982
    Name                      : switch
    Switch Management Address :
    Description               : Linux switch 3.2.65-1+deb7u2+cl2.5+2 #3.2.65-1+deb7u2+cl2.5+2 SMP Mon Jun 1 18:26:59 PDT 2015 x86_64
    Object ID                 : enterprises.40310
    Contact Information       : Admin <>
    Location Information      : Raleigh, NC
    Services                  : 72
    Switch Vendor Name        : Unknown
    Port Ids                  : 00051a76-f711-89b6-0000-000000003bac::5f13678e-6ffd-4b33-912f-f1aa6e8da982:52, 00051a76-f711-89b6-0000-000000003bac::5f13678e-6ffd-4b33-912f-f1aa6e8da982:53, 00051a76-f711-89b6-0000-000000003bac::5f13678e-6ffd-4b33-912f-f1aa6e8da982:54, 00051a76-f711-89b6-0000-000000003bac::5f13678e-6ffd-4b33-912f-f1aa6e8da982:55


To help visualize the following diagram is provided:

Nutanix NodePhysical PortCumulus RMP Port
Node A (Green)vmnic2swp49
Node B (Blue)vmnic2swp50
Node C (Red)vmnic2swp51
Node D (Yellow)vmnic2swp52

Enabling LLDP/CDP on VMware ESXi (Hypervisor on Nutanix)

  1. Follow the directions on one of the following websites to enable CDP:



      e.g. Switch CDP on:

      root@NX-1050-A:~] esxcli network vswitch standard set -c both -v vSwitch0

      Then confirm it is running:

      root@NX-1050-A:~] esxcli network vswitch standard list -v vSwitch0
         Name: vSwitch0
         Class: etherswitch
         Num Ports: 4082
         Used Ports: 12
         Configured Ports: 128
         MTU: 1500
         CDP Status: both
         Beacon Enabled: false
         Beacon Interval: 1
         Beacon Threshold: 3
         Beacon Required By:
         Uplinks: vmnic3, vmnic2, vmnic1, vmnic0
         Portgroups: VM Network, Management Network

      The both means CDP is now running, and the lldpd dameon on Cumulus RMP is capable of “seeing” CDP devices.

  2. After the next CDP interval, the Cumulus RMP box will pick up the interface via the lldp daemon:

    cumulus@switch$ lldpctl show neighbor swp49
    LLDP neighbors:
    Interface:    swp49, via: CDPv2, RID: 6, Time: 0 day, 00:34:58
        ChassisID:    local NX-1050-A
        SysName:      NX-1050-A
        SysDescr:     Releasebuild-2494585 running on VMware ESX
        Capability:   Bridge, on
        PortID:       ifname vmnic2
        PortDescr:    vmnic2
  3. Use netshow to look at lldp information:

    cumulus@switch$ netshow lldp
    To view the legend,  rerun "netshow" cmd with the  "--legend" option
    Local Port    Speed        Mode             Remote Port    Remote  Host       Summary
    ------------  -----------  ---------  ----  -------------  -----------------  --------------------------
    eth0          1G           Mgmt       ====  swp32          swoob.vsokt.local  IP:
    swp49         10G(SFP+)    Access/L2  ====  vmnic2         NX-1050-A          Untagged: br-ntnx
    swp50         10G(SFP+)    Access/L2  ====  vmnic2         NX-1050-B          Untagged: br-ntnx
    swp51         10G(SFP+)    Access/L2  ====  vmnic2         NX-1050-C          Untagged: br-ntnx
    swp52         10G(SFP+)    Access/L2  ====  vmnic2         NX-1050-D          Untagged: br-ntnx

Enabling LLDP/CDP on Nutanix Acropolis (Hypervisor on Nutanix Acropolis)

Nutanix Acropolis is an alternate hypervisor that Nutanix supports. Acropolis Hypervisor uses the yum packaging system and is capable of installing normal Linux lldp daemons to operating just like Cumulus RMP. LLDP should be enabled for each interface on the host. Refer to for setup instructions.

snmpwalk the Switch from Another Linux Device

One of the most important ways to troubleshoot is to snmpwalk the switch from another Linux device that can reach the switch running Cumulus RMP. For this demonstration, another switch running Cumulus RMP within the network is used.

  1. Open /etc/apt/sources.list in an editor.

  2. Add the following line, and save the file:

    deb jessie main non-free
  3. Update the switch:

    cumulus@switch2$ sudo apt-get update
  4. Install the snmp and snmp-mibs-downloader packages:

    cumulus@switch2$ sudo apt-get install snmp snmp-mibs-downloader
  5. Verify that the “mibs :” line is commented out in /etc/snmp/snmp.conf:

    # As the snmp packages come without MIB files due to license reasons, loading
    # of MIBs is disabled by default. If you added the MIBs you can reenable
    # loading them by commenting out the following line.
    #mibs :
  6. Perform an snmpwalk on the switch. The switch running snmpd in the demonstration is using IP address It is possible to snmpwalk the switch from itself, following these instructions, ruling out an snmp problem vs networking problem.

    cumulus@switch2$ snmpwalk -c public -v2c
    Output Examples
    IF-MIB::ifPhysAddress.2 = STRING: 74:e6:e2:f5:a2:80
    IF-MIB::ifPhysAddress.3 = STRING: 0:e0:ec:25:b8:54
    IF-MIB::ifPhysAddress.4 = STRING: 74:e6:e2:f5:a2:81
    IF-MIB::ifPhysAddress.5 = STRING: 74:e6:e2:f5:a2:82
    IF-MIB::ifPhysAddress.6 = STRING: 74:e6:e2:f5:a2:83
    IF-MIB::ifPhysAddress.7 = STRING: 74:e6:e2:f5:a2:84
    IF-MIB::ifPhysAddress.8 = STRING: 74:e6:e2:f5:a2:85
    IF-MIB::ifPhysAddress.9 = STRING: 74:e6:e2:f5:a2:86
    IF-MIB::ifPhysAddress.10 = STRING: 74:e6:e2:f5:a2:87
    IF-MIB::ifPhysAddress.11 = STRING: 74:e6:e2:f5:a2:88
    IF-MIB::ifPhysAddress.12 = STRING: 74:e6:e2:f5:a2:89
    IF-MIB::ifPhysAddress.13 = STRING: 74:e6:e2:f5:a2:8a
    IF-MIB::ifPhysAddress.14 = STRING: 74:e6:e2:f5:a2:8b
    IF-MIB::ifPhysAddress.15 = STRING: 74:e6:e2:f5:a2:8c
    IF-MIB::ifPhysAddress.16 = STRING: 74:e6:e2:f5:a2:8d
    IF-MIB::ifPhysAddress.17 = STRING: 74:e6:e2:f5:a2:8e
    IF-MIB::ifPhysAddress.18 = STRING: 74:e6:e2:f5:a2:8f
    IF-MIB::ifPhysAddress.19 = STRING: 74:e6:e2:f5:a2:90

Any information gathered here should verify that snmpd is running correctly on the Cumulus RMP side, reducing locations where a problem may reside.

Troubleshooting Tips Table for snmp walks

Run snmpwalk from

If it works

If it does not work

switch (switch to be monitored)

snmpd is serving information correctly
Problem resides somewhere else (e.g. network connectivity, Prism misconfiguration)

Is snmpd misconfigured or installed incorrectly?

switch2 (another Cumulus RMP switch in the network)

snmpd is serving information correctly and network reachability works between switch and switch2
Problems resides somewhere else (e.g. can Prism reach switch, Prism misconfiguration)

Network connectivity is not able to grab information?
Is there an iptables rule blocking? Is the snmp walk being run correctly?

Nutanix Prism CLI (ssh to the cluster IP address)

snmpd is serving information correctly and network reachability works between switch and the Nutanix Appliance Problems resides somewhere else (e.g. The GUI might be misconfigured)

Is the right community name being used in the GUI? Is snmp v2c being used?

Troubleshooting Connections without LLDP or CDP

  1. Find the MAC address information in the Prism GUI, located in: Hardware -> Table -> Host -> Host NICs

  2. Select a MAC address to troubleshoot (e.g. 0c:c4:7a:09:a2:43 represents vmnic0 which is tied to NX-1050-A).

  3. List out all the MAC addresses associated to the bridge:

    cumulus@switch$ brctl showmacs br-ntnx
    port name mac addr     vlan    is local?   ageing timer
    swp9      00:02:00:00:00:06 0   no        66.94
    swp52     00:0c:29:3e:32:12  0   no         2.73
    swp49     00:0c:29:5a:f4:7f  0   no         2.73
    swp51     00:0c:29:6f:e1:e4  0   no         2.73
    swp49     00:0c:29:74:0c:ee  0   no         2.73
    swp50     00:0c:29:a9:36:91  0   no         2.73
    swp9      08:9e:01:f8:8f:0c  0   no        13.56
    swp9      08:9e:01:f8:8f:35  0   no         2.73
    swp4      0c:c4:7a:09:9e:d4  0   no        24.05
    swp1      0c:c4:7a:09:9f:8e  0   no        13.56
    swp3      0c:c4:7a:09:9f:93  0   no        13.56
    swp2      0c:c4:7a:09:9f:95  0   no        24.05
    swp52     0c:c4:7a:09:a0:c1  0   no         2.73
    swp51     0c:c4:7a:09:a2:35  0   no         2.73
    swp49     0c:c4:7a:09:a2:43  0   no         2.73
    swp9      44:38:39:00:82:04  0   no         2.73
    swp9      74:e6:e2:f5:a2:80  0   no         2.73
    swp1      74:e6:e2:f5:a2:81  0   yes        0.00
    swp2      74:e6:e2:f5:a2:82  0   yes        0.00
    swp3      74:e6:e2:f5:a2:83  0   yes        0.00
    swp4      74:e6:e2:f5:a2:84  0   yes        0.00
    swp5      74:e6:e2:f5:a2:85  0   yes        0.00
    swp6      74:e6:e2:f5:a2:86  0   yes        0.00
    swp7      74:e6:e2:f5:a2:87  0   yes        0.00
    swp8      74:e6:e2:f5:a2:88  0   yes        0.00
    swp9      74:e6:e2:f5:a2:89  0   yes        0.00
    swp10     74:e6:e2:f5:a2:8a  0   yes        0.00
    swp49     74:e6:e2:f5:a2:b1  0   yes        0.00
    swp50     74:e6:e2:f5:a2:b2  0   yes        0.00
    swp51     74:e6:e2:f5:a2:b3  0   yes        0.00
    swp52     74:e6:e2:f5:a2:b4  0   yes        0.00
    swp9      8e:0f:73:1b:f8:24  0   no         2.73
    swp9      c8:1f:66:ba:60:cf  0   no        66.94

    Alternatively, you can use grep:p

    cumulus@switch$ brctl showmacs br-ntnx | grep 0c:c4:7a:09:a2:43
    swp49     0c:c4:7a:09:a2:43   0   no         4.58

    vmnic1 is now hooked up to swp49. This matches what is seen in lldp:

    cumulus@switch$ lldpctl show neighbor swp49
    LLDP neighbors:
    Interface:    swp49, via: CDPv2, RID: 6, Time: 0 day, 01:11:12
        ChassisID:    local NX-1050-A
        SysName:      NX-1050-A
        SysDescr:     Releasebuild-2494585 running on VMware ESX
        Capability:   Bridge, on
        PortID:       ifname vmnic2
        PortDescr:    vmnic2

SNMP Traps


The Net-SNMP trap daemon configuration file, /etc/snmptrapd.conf, is used to configure how incoming traps should be processed. For more information about specific configuration options within the file, run the following command in a terminal:

cumulus@switch:~$ man 5 snmptrapd.conf

# EXAMPLE-trap.conf:
#   An example configuration file for configuring the Net-SNMP snmptrapd agent.
# This file is intended to only be an example.  If, however, you want
# to use it, it should be placed in /etc/snmp/snmptrapd.conf.
# When the snmptrapd agent starts up, this is where it will look for it.
# All lines beginning with a '#' are comments and are intended for you
# to read.  All other lines are configuration commands for the agent.

# PLEASE: read the snmptrapd.conf(5) manual page as well!
snmpTrapdAddr localhost
forward default {{global['snmp_server']}}

Generating Event Notification Traps

The Net-SNMP agent provides a method to generate SNMP trap events, via the Distributed Management (DisMan) Event MIB, for various system events, including linkup/down, exceeding the temperature sensor threshold, CPU load, or memory threshold, or other SNMP MIBs.

Enabling MIB to OID Translation

MIB names can be used instead of OIDs, by installing the snmp-mibs-downloader, to download SNMP MIBs to the switch prior to enabling traps. This greatly improves the readability of the snmpd.conf file.

  1. Open /etc/apt/sources.list in a text editor.

  2. Add the non-free repository, and save the file:

    cumulus@switch:~$ deb jessie main non-free
  3. Update the switch:

    cumulus@switch:~$ apt-get update
  4. Install the snmp-mibs-downloader:

    apt-get snmp-mibs-downloader
  5. Open the /etc/snmp/snmp.conf file to verify that the mibs : line is commented out:

    # As the snmp packages come without MIB files due to license reasons, loading
    # of MIBs is disabled by default. If you added the MIBs you can reenable
    # loading them by commenting out the following line.
    #mibs :
  6. Open the /etc/default/snmpd file to verify that the export MIBS= line is commented out:

    # This file controls the activity of snmpd and snmptrapd
    # Don't load any MIBs by default.
    # You might comment this lines once you have the MIBs Downloaded.
    #export MIBS=
  7. Once the configuration has been confirmed, remove or comment out the non-free repository in /etc/apt/sources.list.

    #deb jessie main non-free

Configuring Trap Events

The following configurations should be made in /etc/snmp/snmp.conf, in order to enable specific types of traps. Once configured, restart the snmpd service to apply the changes.

cumulus@switch:~$ sudo systemctl restart snmpd.service

Defining Access Credentials

An SNMPv3 username is required to authorize the DisMan service. The example code below uses cumulusUser as the username.

createUser cumulusUser
iquerySecName cumulusUser
rouser cumulusUser

Defining Trap Receivers

The example code below creates a trap receiver that is capable of receiving SNMPv2 traps.

trap2sink public

Although the traps are sent to an SNMPV2 receiver, the SNMPv3 user is still required.

It is possible to define multiple trap receivers, and to use the domain name instead of IP address in the trap2sink directive.

Configuring LinkUp/Down Notifications

The linkUpDownNotifications directive is used to configure linkup/down notifications when the operational status of the link changes.

linkUpDownNotifications yes

The default frequency for checking link up/down is 60 seconds. The default frequency can be changed using the monitor directive directly instead of the linkUpDownNotifications directive. See man snmpd.conf for details.

Configuring Temperature Notifications

Temperature sensor information for each available sensor is maintained in the the lmSensors MIB. Each platform may contain a different number of temperature sensors. The example below generates a trap event when any temperature sensors exceeds a threshold of 68 degrees (centigrade). It monitors each lmTempSensorsValue. When the threshold value is checked and exceeds the lmTempSensorsValue, a trap is generated. The -o lmTempSenesorsDevice option is used to instruct SNMP to also include the lmTempSensorsDevice MIB in the generated trap. The default frequency for the monitor directive is 600 seconds. The default frequency may be changed using the -r option.:

monitor lmTemSensor -o lmTempSensorsDevice lmTempSensorsValue > 68000

Alternatively, temperature sensors may be monitored individually. To monitor the sensors individually, first use the sensors command to determine which sensors are available to be monitored on the platform.

Adapter: i2c-0-mux (chan_id 2)
fan5: 7006 RPM (min = 2500 RPM, max = 23000 RPM)
fan6: 6955 RPM (min = 2500 RPM, max = 23000 RPM)
fan7: 6799 RPM (min = 2500 RPM, max = 23000 RPM)
fan8: 6750 RPM (min = 2500 RPM, max = 23000 RPM)
temp1: +34.0 C (high = +68.0 C)
temp2: +28.0 C (high = +68.0 C)
temp3: +33.0 C (high = +68.0 C)
temp4: +31.0 C (high = +68.0 C)
temp5: +23.0 C (high = +68.0 C)

Configure a monitor command for the specific sensor using the -I option. The -I option indicates that the monitored expression is applied to a single instance. In this example, there are five temperature sensors available. The following monitor directive can be used to monitor only temperature sensor three at five minute intervals.

monitor -I -r 300 lmTemSensor3 -o lmTempSensorsDevice.3 lmTempSensorsValue.3 > 68000

Configuring Free Memory Notifications

You can monitor free memory using the following directives. The example below generates a trap when free memory drops below 1,000,000KB. The free memory trap also includes the amount of total real memory:

monitor MemFreeTotal -o memTotalReal memTotalFree <  1000000

Configuring Processor Load Notifications

To monitor CPU load for 1, 5 or 15 minute intervals, use the load directive in conjunction with the monitor directive. The following example will generate a trap when the 1 minute interval reaches 12%, the 5 minute interval reaches 10% or the 15 minute interval reaches 5%.

load 12 10 5
monitor -r 60 -o laNames -o laErrMessage "laTable" laErrorFlag !=0

Configuring Disk Utilization Notifications

To monitor disk utilization for all disks, use the includeAllDisks directive in conjunction with the monitor directive. The example code below generates a trap when a disk is 99% full:

includeAllDisks 1%
monitor -r 60 -o dskPath -o DiskErrMsg "dskTable" diskErrorFlag !=0

Configuring Authentication Notifications

To generate authentication failure traps, use the authtrapenable directive:

authtrapenable 1

Supported MIBs

Below are the MIBs supported by Cumulus RMP, as well as suggested uses for them. The overall Cumulus RMP MIB is defined in /usr/share/snmp/Cumulus-Snmp-MIB.txt.

MIB NameSuggested Uses
BRIDGE and Q-BRIDGEThe dot1dBasePortEntry and dot1dBasePortIfIndex tables in the BRIDGE-MIB and dot1qBase, dot1qFdbEntry, dot1qTpFdbEntry, dot1qTpFdbStatus, and the dot1qVlanStaticName tables in the Q-BRIDGE-MIB tables. You must uncomment the pass_persist script in /etc/snmp/snmpd.conf.
CUMULUS-COUNTERS-MIBDiscard counters: Cumulus RMP also includes its own counters MIB, defined in /usr/share/snmp/Cumulus-Counters-MIB.txt. It has the OID .
CUMULUS-RESOURCE-QUERY-MIBCumulus RMP includes its own resource utilization MIB, which is similar to using cl-resource-query. It monitors L3 entries by host, route, nexthops, ECMP groups and L2 MAC/BDPU entries. The MIB is defined in /usr/share/snmp/Cumulus-Resource-Query-MIB.txt, and has the OID .
DISMAN-EVENTTrap monitoring
ENTITYFrom RFC 4133, the temperature sensors, fan sensors, power sensors, and ports are covered.
ENTITY-SENSORPhysical sensor information (temperature, fan, and power supply) from RFC 3433.
HOST-RESOURCESUsers, storage, interfaces, process info, run parameters
IF-MIBInterface description, type, MTU, speed, MAC, admin, operation status, counters
IP (includes ICMP)IPv4, IPv4 addresses, counters, netmasks
IPv6IPv6 counters
IP-FORWARDIP routing table
LLDPL2 neighbor info from lldpd (note, you need to enable the SNMP subagent in LLDP). lldpd needs to be started with the -x option to enable connectivity to snmpd (AgentX).
LM-SENSORS MIBFan speed, temperature sensor values, voltages. This is deprecated since the ENTITY-SENSOR MIB has been added.
NET-SNMP-AGENTAgent timers, user, group config
NET-SNMP-EXTENDAgent timers, user, group config
NET-SNMP-EXTEND-MIB(See also this knowledge base article on extending NET-SNMP in Cumulus RMP to include data from power supplies, fans and temperature sensors.)
NET-SNMP-VACMAgent timers, user, group config
SNMP-MPDUsers, access
SNMPv2SNMP counters (For information on exposing CPU and memory information via SNMP, see this knowledge base article.)
TCPTCP related information
UCD-SNMPSystem memory, load, CPU, disk IO
UDPUDP related information

The ENTITY MIB does not currently show the chassis information in Cumulus RMP 3.0.