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The output of netstat -rn on my FreeBSD virtual machine shows that:

Internet:
Destination        Gateway            Flags      Netif Expire
default            10.195.51.254      UGS      vtnet0
10.195.48.0/22     link#1             U        vtnet0
10.195.49.46       link#1             UHS         lo0
127.0.0.1          link#2             UH          lo0
132.148.77.28      link#1             UHS         lo0
132.148.77.28/32   link#1             U        vtnet0

Given the CIDR of 32, doesn't 132.148.77.28/32 equal 132.148.77.28? If so, how do packets to the destination address in question decide whether to use lo0 or vtnet0 since there's two different routes defined for that address?

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1 Answer 1

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The H flag indicates a route to a particular host, which will be used in preference to a route to a subnet.

It looks like the main subnet for vtnet0 is 10.195.48.0/22, and 132.148.77.28 is just an alias (hence the /32).

See the manual pages for netstat(1) and route(8).

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  • Is the Netif column for the interface that the packet is coming from? As in, any packet passing through lo0 bound for 132.148.77.28 will send it to link#1, and any packet passing through vtnet0 bound for 132.148.77.28 will also send it to link#1? OR, are you saying that it doesn't matter where it comes from, the preferred route will always be the one with UHS flags - in which case what would the Netif value do?
    – papiro
    Commented Feb 12, 2017 at 2:42
  • A packet arriving on any interface for the host has arrived and doesn't need to be routed anywhere. If you need a deeper understanding of the network interface, you could look at The Design and Implementation of the FreeBSD Operating System (book) Commented Feb 12, 2017 at 7:56

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