Let's say that we have two PC's and one router between them:
PC1 ----------- Router ---------- PC2
PC 1 MTU is 400 bytes PC 2 MTU is 1500 bytes
We send a packet from PC1(400) to PC2(1500)
The question is: Will there be any packet fragmentation/byte excess - how the router will act in this situation?
In my opinion - no, but shouldn't it fill the data with zeros, or something?
Also, how the fragmentation works, if we switch the MTU's between two of them?