Troubleshooting “No buffer space available” Errors

On occasion traffic on a NIC may have trouble getting out with an error similar to:

ping: sendto: No buffer space available

Or:

dpinger WANGW x.x.x.x: sendto error: 55

The most common causes of this are:

  • No route to the target network (or no default route)

  • Missing link route for a local target

  • Stale state in pf sending the connection out an invalid path (reset states)

  • Network memory buffer exhaustion

    See also

    See Hardware Tuning and Troubleshooting

  • Faulty NIC and/or driver issue

    Sometimes resetting the NIC can bring it back again:

    # ifconfig ix3 down; ifconfig ix3 up

  • Faulty cable

  • Traffic shaping (ALTQ or Limiters) dropping the packet

  • Virtual NIC being throttled by the hypervisor or host, such as an AWS instance using more throughput than an instance size can support

    In this case, change the throttling in the host (not guest) or upgrade to a larger instance/higher tier on a hosted platform such as AWS.

  • Virtual NIC being disconnected/disabled in certain hypervisors

  • An otherwise overloaded NIC exhausting its send/recv buffers

  • Other various switch/buffer/connectivity issues

Trying to bounce the NIC with ifconfig is the easiest thing to try first. After that, save/apply the interface settings on each interface (or at least WANs and the LAN in question). Check/(re)set the default route if it has been lost. Reset States. Replacing the cable may also help. Removing traffic shaping if it is enabled is also a good test.

Otherwise investigate the traffic on the NIC and look for other buffer-related causes. Seek help from Netgate TAC for assistance in diagnosing the issue, or post on the forum/mailing list.