Switching & Troubleshooting

This tag is associated with 12 posts

Flow Control – Pause Frames

. When an Ethernet device gets over loaded, flow control allows it to send PAUSE requests to the  devices sending it data to allow the over loaded condition to clear.  If flow control is not enabled and an over loaded condition occurs, the device will drop packets. Dropping packets is much more performance impacting than flow control. 802.3X flow … Continue reading

Layer 2 Discards Troubleshooting – RX TX Discards

. The following list of questions/vectors can assist in troubleshooting Layer 2 discard issues. They have been of help to me in the past on more than one occasion. What Switches/Models? What firmware versions? Look at the subsequent firmwares’ release notes for any identified issues, resolved caveats etc. that match what you re experiencing. What … Continue reading

Switch Port auto shuts/ port shuts itself down – Troubleshooting

. Following is a list of vectors that may assist in troubleshooting issues where the port behavior look like it is shutting itself down. Cable/ Power Management. A link light does not guarantee that the cable is fully functional. The cable could have encountered physical stress that causes it to be functional at a marginal … Continue reading

Layer 3 Switching

. The major difference between a router and an L3 switch is that packet switching in a router is done in software by microprocessor-based engines, whereas packet switching in an L3 switch is done in hardware by specific Application Specific Integrated Circuits (ASICs). Layer 2 switches operate well with reasonably sized broadcast domains/VLANs. The routing … Continue reading

PowerConnect Switch Hang/Freeze – Management Interface unresponsive Troubleshooting

. Are you connecting to the switch via the console port(and if so, are you using the null modem cable provided, or another solution), or is this a telnet/ssh connection that you’re establishing to manage the switch?  If you are connecting via telnet, do we see the same results if we use the console port?   … Continue reading

Infiniband Troubleshooting

  This comes from a stack of notes i compiled when faced with issues on an infiniband deployment that needed troubleshooting. 1)    InfiniBand Hardware Checks  Carry out the following hardware checks: a)      Make sure that the InfiniBand switches are powered up. b)      Make sure that the each machine is powered up. c)      Make sure that … Continue reading

Cisco and Force10 – STP Spanning Tree Interoperability

. Cisco Implements a proprietary flavor of spanning tree protocol, which is Per-VLAN in nature. This gives rise to certain considerations in a multi-vendor environment. Any third party switches that implement STP based on the IEEE standard, have a spanning tree implementation that has a single instance span the entire switch, regardless of the number of VLANs … Continue reading

Powerconnect SFP/Fiber connectivity – Options, Requirements and Troubleshooting

Basic requirements for fiber connections on PowerConnect switches: MMF optical cables, LC connectors, and SFP transceivers. 1)     Optical Cables :   Single Mode Vs Multi Mode Single Mode cable has a diameter of 8.3 to 10 microns, through which only one mode will propagate, typically 1310 or 1550nm. SMF gives you a higher transmission rate and up to … Continue reading

Latency, Packet loss Troubleshooting (PowerConnect, Others)

. First, know your network. know the topology. if you have a network in place where by design, the majority of the variables are deterministic & not left to chance, the task gets a lot simpler. with this out of the way, the following are the different outputs and avenues that might shed further light … Continue reading

Powerconnect Switches: Oversized Packet Counter, bcmRX task

. In a blade chassis implementation some time ago, some concerns were raised on the value of packet counters, and an inquiry on the bcmRX task. the notes i compiled as part of my reply, are as below: The Oversized Packets counter can be safely ignored, as it is not indicative of a problem. What … Continue reading