min_pmtu - INTEGER
default 562 - minimum discovered Path MTU
+route/max_size - INTEGER
+ Maximum number of routes allowed in the kernel. Increase
+ this when using large numbers of interfaces and/or routes.
+
+neigh/default/gc_thresh3 - INTEGER
+ Maximum number of neighbor entries allowed. Increase this
+ when using large numbers of interfaces and when communicating
+ with large numbers of directly-connected peers.
+
mtu_expires - INTEGER
Time, in seconds, that cached PMTU information is kept.