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30 .\" @(#)lo.4 8.1 (Berkeley) 6/5/93
38 .Nd software loopback network interface
44 interface is a software loopback mechanism which may be
45 used for performance analysis, software testing, and/or local
47 As with other network interfaces, the loopback interface must have
48 network addresses assigned for each address family with which it is to be used.
50 may be set with the appropriate
52 commands for corresponding address families.
53 The loopback interface should be the last interface configured,
54 as protocols may use the order of configuration as an indication of priority.
57 be configured first unless no hardware
60 If the transmit checksum offload capability flag is enabled on a loopback
61 interface, checksums will not be generated by IP, UDP, or TCP for packets
62 sent on the interface.
64 If the receive checksum offload capability flag is enabled on a loopback
65 interface, checksums will not be validated by IP, UDP, or TCP for packets
66 received on the interface.
68 By default, both receive and transmit checksum flags will be enabled, in
69 order to avoid the overhead of checksumming for local communication where
70 data corruption is unlikely.
71 If transmit checksum generation is disabled, then validation should also be
72 disabled in order to avoid packets being dropped due to invalid checksums.
75 .It lo%d: can't handle af%d.
76 The interface was handed
77 a message with addresses formatted in an unsuitable address
78 family; the packet was dropped.
89 The current checksum generation and validation avoidance policy appeared in