Tag Archives: pmtud

MTU and PMTU on JunOS

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;

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