On 2019-10-10, Russell Sutherland <russell.sutherl...@utoronto.ca> wrote: > I've set up a L2overL3 tunnel using the template as found in "man etherip". I > am running OpenBSD 5.9, which I believe is the first version to support the > etherip interface. > > I find the bridge/tunnel does not pass a small range of specific sized > packets. > > E.g. if 1.2.3.4 is at the far end of the tunnel and I am pinging from the > local end: > > ping -s 1388 1.2.3.4 works > ping -s 1396 1.2.3.4 works > > All other sizes, 1389 to 1395 inclusive fail. > > Is there some way to remedy this?
If you have different MTUs each side (e.g. common if one end uses pppoe), or if there is a link between the two tunnel endpoints with restricted MTU (which you might not notice for TCP connections because it may rewrite the MSS value), then reduce MTU on the endpoints to the lowest common denominator.
