Path MTU on Linux when there are multiple routes with different MTUs
On my Linux (actually OpenWrt) device, I have two default routes: root@<>:~# ip route default via 10.111.7.76 dev eth1 proto static metric 10 linkdown default via <redacted> dev wwan0 proto static src <redacted> metric 40 eth1 has an MTU of 1500 and wwan0 has an MTU of 1300. eth1 is currently down and hence the linkdown in the output above.