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
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 Tuning and Troubleshooting Network Cards
Faulty NIC and/or driver issue
Sometimes resetting the NIC can bring it back again:
# ifconfig em3 down; ifconfig em3 up
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.