How to troubleshoot “No buffer space available” Errors on Netgate Router

Authored by: Support.com Tech Pro Team

1. Introduction

How to troubleshoot “No buffer space available” Errors on Netgate Router

2. Resolution

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 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
• 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 switches/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.