Appendix G: Appliance Troubleshooting
G.1 LAN performance
If you're experiencing issues between the appliance and the network, issue the ethtool eth0 or ethtool eth1 command to
determine if the appliance is communicating with the network switch at half duplex. This can happen if the network switch is
not set to auto-negotiate speed and duplex (the appliance only supports auto). When a network switch is static and the
appliance is auto, the two will not be able to communicate with matching duplex, leading to poor network peformance.
To resolve this, have the network administrator set the network switch port to auto-negotiate speed and duplex.
To assist in troubleshooting issues related to connectivity, sessions, time-outs or other network-related problems, a network
traffic packet capture may be performed. At the appliance shell, execute the tcpdump command on one interface at a time
that lies within the communication path between the user-appliance and the appliance-target. Save the output of the
tcpdump to the /download directory, then copy the output file to a workstation for analysis using tools such as WinSCP and
Wireshark.
For example, to capture from both the eth0 and the priv interfaces:
tcpdump -i eth0 -w /download/networktrace1.cap and tcpdump -i priv -w /download/networktrace2.cap
G.2 WAN performance
If KVM, virtual media or firmware uploads are slow or fail across a network WAN, many network routers that connect to WAN
links (Frame Relay, ATM, SONET or VPN) often are set to fragment large IP packets into smaller chunks. The maximum size
of an IP packet is defined as MTU within all devices connecting to networks. The appliance's MTU defaults to 1500 bytes
and the appliance sends all traffic with the "Don't Fragment" bit enabled in the IP header. An IP packet that doesn't want to
be fragmented is discarded by a router that must fragment large packets before transmitting them across a WAN link.
To resolve this, you can decrease the size of the appliance's MTU in the network settings, which will generate smaller IP
packets. This will increase the total number of packets that get created, but they will be small enough to cross the WAN link
without being discarded and should improve the situation. Don't do this unless you are sure that the appliance traffic is
being discarded by the customer WAN router because of fragmentation.
G.3 Launching a KVMsession
If the ActiveXKVMviewer does not install when launching a KVMsession from the appliance web UI, try the following:
• When starting the browser, right-click the browser shortcut and select Run as administrator. Then launch
theKVMsession again.
NOTE: Once the viewer has been installed, it is no longer necessary to start the browser in administrator mode.
• Add the appliance's full address (for example, https://10.207.26.7)to the browser's Trusted Sites list.
G.4 Bridge groups
When creating a bridge group inside of the appliance, there is a default setting to "Enable STP." STP (Spanning Tree
Protocol) is a network switch methodology for eliminating switching loops caused by redundant network connections. STP
requires network switches to send out a BPDU (bridging protocol data unit) which is essentially an ID that identifies the
sending switch.
All switches receive these BPDUs across all connections to that switch and compare it to their own BPDU. If the same BPDU
comes in on more than one connection, the switch determines one of those connections to be redundant and it will disable
that link. This can happen if you connect two appliance ports to a network switch and place both of the appliance ports into
a single bridge group. Most enterprise network switches have a feature called BPDU_guard which is intended to be enabled
on ports that are not supposed to be connected to other network switches (Cisco Nexus switches enable this feature by
default on all interfaces).
If you connect an appliance to a switch with the BPDU_guard active, then you must disable STP if you plan to create a
bridge group on that appliance. If you don't disable STP, the network switch will disable its connection to the appliance
when a bridge group is created. It will do this because the appliance will send out its own BPDU when the STP option is
enabled.
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