Hello,
In the configuration MTU of GRE interface is 1480:
[MikroTik_1] /routing ospf neighbor> /interface gre print
Flags: X - disabled, R - running
0 R ;;; Tunnel 1
name=“gre-tunnel1” mtu=1480 actual-mtu=1480 local-address=XX.XX.XX.XX
remote-address=YY.YY.YY.YY keepalive=10s,10 dscp=inherit clamp-tcp-mss=yes
dont-fragment=no allow-fast-path=yes
But, when OSPF adjacency on this router cannot be established with messages:
18:52:52 route,ospf,info Discarding Database Description packet: too large MTU
18:52:52 route,ospf,info mine=1440
18:52:52 route,ospf,info received=1480
Why OSPF decides MTU is 1440, but not 1480?
Other point, it seems MTU can be changed, because before this message it works with MTU 1460 on other router interface.
Could you clarify, why?
Regards,
MMS101