I would like to talk about couple of things in this post about MTU on JunOS;
- Why do we have two different MTU settings i.e at interface and logical level?
- What is the meaning of path mtu discovery on a junos box
- How MTU is important for OSPF?
Actually all started with my OSPF tests in my lab. I was connected to one SRX device in my home network and playing with MTU settings at interface level and unit level to see the differences and all of a sudden I lost my connection. To be honest I like doing non-destructive mistakes as they teach me a lot. Now I recall again how MTU is an important piece in OSPF messages. Lets start from beginning again;
root@srx# run show interfaces ge-0/0/1
Physical interface: ge-0/0/1, Enabled, Physical link is Up
Link-level type: Ethernet, MTU: <strong>1000</strong>, Speed: 1000mbps,
Logical interface ge-0/0/1.0 (Index 73) (SNMP ifIndex 515)
Protocol inet, MTU: <strong>986</strong>
Addresses, Flags: Is-Preferred Is-Primary
Destination: 192.168.195/24, Local: 192.168.195.2, Broadcast: 192.168.195.255