ENH500

1 Using SNMP with an Engenius ENH500 wireless access point

1 Using SNMP with an Engenius ENH500 wireless access point

This quick guide shows how to configure SNMP support for an Engenius ENH500 wireless access point. It shows you how to remotely reboot the ENH500 access point using SNMP. It will probably work with other Engenius wireless products. Rebooting the device is helpful since over time its performance slows to a crawl. Perhaps it has a memory leak? There is an option for an auto-reboot, but this isn't selectable when used in WDS bridge mode.

1.1 Setup

Download required packages. The example below is for Debian-based Linux. You will also need to find the Engenius MIB file on the web.

sudo apt-get install snmp snmp-mibs-downloader
export MIBS="+/home/user/ENGENIUS-PRIVATE-MIB-ENH500_v1.5.2.mib"

Note that the Engenius MIB violates the standard by using underscores in object names. You can work around this by passing the "-Pu" switch to the snmp comamnds.

You may need to allow UDP packets to port 161 on your Linux machine using iptables.

1.2 Useful diagnostic tools

Assuming your ENH500 is at IP address 192.168.1.7.

tcpdump host 192.168.1.7
man snmpcmd

1.3 Enabling snmpv3

The ENH500, at least with Australian firmware 1.5.6, and running in WDS bridge mode, doesn't allow SNMP to be enabled. The solution is to create a backup file, untar it, edit etc/config/snmpd to set "option 'SnmpEnable' '1'", tar it, and then restore.

From the Management, SNMP Settings, menu you need to click v3Enable, select an Auth Key, a Priv Key, and an Engine ID.

1.4 Choosing an engineID

EngineID is a hex string with 11 octets, and is blank by default in the ENH500. You can use whatever hex numbers you want, but you may as well stick to the standard. The first 4 octets are the device's SNMP management private enterprise number, from here: IANA enterprise numbers with the most significant bit of the first octet being 1, e.g., Engenius' number is decimal 44914, which is 0000af72 as 4 octets, so the engineID starts with 8000af72.

The next octet is 03 to indicate that the remaining 8 octets are the MAC address. In this example we will use 88DC12345678. So the final engineID is

8000af720388DC12345678

1.5 Choose an "Auth Key" and a "Priv Key".

In the examples shown here these are shown as "authKey" "privKey".

Click Save/Apply in the Management/SNMP menu.

1.6 To obtain a list of all the top-level SNMP objects

snmpwalk -v 3 -Pu -u admin -a MD5 -A authKey -x DES -X privKey -l AuthPriv 192.168.1.7

1.7 To obtain a list of all the SNMP Engenius private objects

snmpwalk -v 3 -Pu -u admin -a MD5 -A authKey -x DES -X privKey -l AuthPriv 192.168.1.7 ENGENIUS-PRIVATE-MIB-ENH500::engeniusprivate

Unfortunately, there aren't many interesting ones. I would have liked to have been able to read the link strength in dB, and there is reference to RSSI being added to the MIB, but it isn't there.

1.8 To obtain the value of a parameter

snmpget -v 3 -Pu -u admin -a MD5 -A authKey -x DES -X privKey -l AuthPriv 192.168.1.7 wirelessMacAddress.0

1.9 To reboot the device

This is where you need the engineID.

snmpset -v 3 -Pu -u admin -a MD5 -A authKey -x DES -X privKey -l AuthPriv -E 8000af720388DC12345678 192.168.1.7 executeRebootCmd.0 i 1