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it is always said that every host's routing table must have a entry for loop back route as shown below:

Destination     Gateway        Flags  Ref    Use   Interface 
-----------    -----------     -----  ----  -----  ---------       UH      1      298      lo0  

My question is why we need to make such an entry in the routing table even if our loop back interface working well without this.

working well here i mean that i can ping on it and even if i am configuring a http server on my machine and trying to test it with localhost, it is also working well.

note:- i am asking this question in regard of Linux OS.

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If it works without the entry, then clearly, its not required. So whom ever said it was required is clearly wrong. – Ramhound Feb 13 '13 at 14:51
Linux has a implicit routes for its local interfaces - loopback host is, with a /8 netmask, so will (correctly) go to that interface as well, even if netstat -r doesn't show it. Probably whoever told you this has cargo-culted the "knowledge" from some ancient place that no longer exists - there's all sorts of misinformation about networks out there that hasn't been true for 20 years or more. – Gabe Apr 29 '13 at 11:06

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