cisco_R2(config-subif)#do debug ip osp adj OSPF adjacency debugging is on cisco_R2(config-subif)#ip mtu 1111 <<<<<<<<<<<<<<<< cisco_R2(config-subif)# cisco_R2(config-subif)# cisco_R2(config-subif)#do clear ip ospf !!!debug shows this: cisco_R2(config-subif)# *Dec 23 13:02:27.164: OSPF-1 ADJ Et0/0.10: Rcv DBD from 6.6.6.6 seq 0x19FD opt 0x52 flag 0x7 len 32 mtu 1500 state EXSTART <<<<<<<<<<<<< *Dec 23 13:02:27.164: OSPF-1 ADJ Et0/0.10: Nbr 6.6.6.6 has larger interface MTU <<<<<<<<< *Dec 23 13:02:27.164: OSPF-1 ADJ Et0/0.10: Rcv DBD from 6.6.6.6 seq 0x26B opt 0x52 flag 0x2 len 112 mtu 1500 state EXSTART *Dec 23 13:02:27.164: OSPF-1 ADJ Et0/0.10: Nbr 6.6.6.6 has larger interface MTU *Dec 23 13:02:27.395: OSPF-1 ADJ Et0/0.10: Rcv DBD from 6.6.6.6 seq 0x26B opt 0x52 flag 0x2 len 112 mtu 1500 state EXSTART