What is the task TNetTask resonsible for?

  • 8 February 2017
  • 4 replies
  • 320 views

Userlevel 1
Ive found some articles online, nothing of substance however. Only descriptions offered are very vauge like responsible for "switch ethernet traffic". And as a follow up, why would that task suddenly jump on devices from <5% to > 90% then locking up a switch.

4 replies

Userlevel 5
in ExtremeWare, if the tNetTask is spiked up, that means that there is a lot of traffic going to the CPU of the switch. Look for loops in the network.
Userlevel 1
Did, no loops. We even disabled all ports on LAN rtr (the device being bad here) except for the WAN uplink, still did it.....I think, we tried so many things. I know we swapped the device out entirely, same issue. I cant for certain say disabled all ports, a co-worker took over some of the troubleshooting at times. Here an even better one

tNetTask is the central clearing house for all network I/O. A packet
comes in, netJobAdd'ed, and tNetTask does everything for the packet for its lifetime. This is done for all packets, all network interfaces, and the entire TCP/IP stack.

Packet captures are showing nothing of substance.
Userlevel 4
Run the command "top" a few times and check the highest processes
Userlevel 7
Did, no loops. We even disabled all ports on LAN rtr (the device being bad here) except for the WAN uplink, still did it.....I think, we tried so many things. I know we swapped the device out entirely, same issue. I cant for certain say disabled all ports, a co-worker took over some of the troubleshooting at times. Here an even better one

tNetTask is the central clearing house for all network I/O. A packet
comes in, netJobAdd'ed, and tNetTask does everything for the packet for its lifetime. This is done for all packets, all network interfaces, and the entire TCP/IP stack.

Packet captures are showing nothing of substance.
Hi Jimmy,

did you take packet captures on the WAN uplink port and look for potentially problematic traffic? E.g. IP packets with IP options set, or a TTL of 1, or UDP data sent to an IP without ARP entry? Anything that would be forwarded in software?

Switches are not designed for software forwarding, thus "normal" amounts of traffic needing software forwarding might be sufficient to overload the CPU.

Erik

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