List of Routing Table Flags

From the man page:

Letter

Flag

Meaning

1

RTF_PROTO1

Protocol specific routing flag #1

2

RTF_PROTO2

Protocol specific routing flag #2

3

RTF_PROTO3

Protocol specific routing flag #3

B

RTF_BLACKHOLE

Just discard pkts (during updates)

b

RTF_BROADCAST

The route represents a broadcast address

C

RTF_CLONING

Generate new routes on use

c

RTF_PRCLONING

Protocol-specified generate new routes on use

D

RTF_DYNAMIC

Created dynamically (by redirect)

G

RTF_GATEWAY

Destination requires forwarding by intermediary

H

RTF_HOST

Host entry (net otherwise)

L

RTF_LLINFO

Valid protocol to link address translation

M

RTF_MODIFIED

Modified dynamically (by redirect)

R

RTF_REJECT

Host or net unreachable

S

RTF_STATIC

Manually added

U

RTF_UP

Route usable

W

RTF_WASCLONED

Route was generated as a result of cloning

X

RTF_XRESOLVE

External daemon translates proto to link address