Troubleshooting on vlan51

Fixing "Device Denied SNMP Access" Traps in HPE IMC

Wed, 01 Jun 2016 00:00:00 +0000

IMC needs correct SNMP credentials to read the MIBs on each device. When they’re wrong, you’ll see traps like these:

cli

Trap Name: Device Denied SNMP Access
Severity: Major
Trap Time: 2016-05-30 19:41:43
Description: Device "My Network Switch" denied access.

cli

iMC: 10.0.10.10
Trap of Source: MYSWITCH (10.0.10.254)
Location: Home
Contact: "Network Admins"
Trap Name: Authentication Failure
Severity: Warn
Trap Time: 2016-05-31 07:15:23
Description: Device receives an SNMP message with an erroneous community string

These are almost always the device (switch, firewall and so on) refusing IMC’s requests. Check the device’s own logs and you’ll usually find the failures line up with IMC’s polling times.

HPE IMC Installation and Upgrade Errors (and Fixes)

Wed, 01 Jun 2016 00:00:00 +0000

This isn’t a step-by-step install guide. It’s a collection of problems I’ve hit while installing and upgrading IMC, and how I got past them.

Installing: .NET 3.5 “source files could not be found” #

On Windows Server 2012, IMC’s installer needs the .NET Framework 3.5 feature, which can fail to install because the source files can’t be found.

Mount the Windows Server ISO (here as D:) and run this from an elevated command prompt, changing the drive letter if needed:

Command-Line Packet Capture on Citrix NetScaler with nstrace

Thu, 01 Oct 2015 00:00:00 +0000

How to capture packets on a Citrix NetScaler from the command line using nstrace, then open the capture in Wireshark.

Start a capture #

SSH to the NetScaler and, at the > prompt, run nstrace with a filter:

cli

nstrace -filter "DESTIP == 10.0.0.20" -link ENABLED -size 0

-size 0 captures the entire packet. By default NetScaler only captures the headers.

To combine filters, put the whole expression in quotes and separate conditions with || (or &&):

Tuning Link Up/Down Flap Alarms in HPE IMC

Thu, 01 Jan 2015 00:00:00 +0000

IMC raises this alarm when a port flaps:

cli

iMC alarm system found event (Link UP) and event (Link DOWN) had 3 intermittent failures from <date/time> to <date/time>

Investigate before tuning #

Don’t dismiss link flaps. Find the device and port in the alarm, log into the switch, and check the log (newest first on ArubaOS-Switch):

cli

show logging -r

Look for errors like this one, which point to a real physical problem you need to fix: