Difference between gateway PMTU and tunnel MTU for a BOVPN Virtual Interface?


I had a problem with dropped packages on a BOVPN configured with a Virtual Interface, I fixed it by lowering the tunnel MTU for the VPN to the right value.

I later found that in the Virtual Interface configuration, in the gateway advances settings there is a field to setup a PMTU and I am now wondering what is the difference and which one is the better option.

Is it that PMTU allows you to have a different MTU per gateway vs for the whole tunnel? and if you only have one gateway, is there any preference on where to set this up?

I ask specifically because given that I'm running 12.5.3 I had to set the tunnel MTU using the CLI so I guess that setting change is not saved as part of the configuration file which may cause trouble later if I for example upgrade the hardware and forget to set this manually again...


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