'Why router can use layer 4 infomation in emcp hash?

Router is layer 3 device, but it can use layer 4 info (like:dst.port, src.port, protocol) in ecmp hash function. Why?

networking network-programming load-balancing router

Solution 1:^[1]

Because it cheats and looks at that information. Nothing is stopping it.

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Source: Stack Overflow

Solution	Source
Solution 1	user253751