1ROUTED(8) System Manager's Manual ROUTED(8)
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6 routed - network routing daemon
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9 routed [ -d ] [ -g ] [ -s ] [ -q ] [ -t ] [ logfile ]
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12 Routed is invoked at boot time to manage the network routing tables.
13 The routing daemon uses a variant of the Xerox NS Routing Information
14 Protocol in maintaining up to date kernel routing table entries. It
15 used a generalized protocol capable of use with multiple address types,
16 but is currently used only for Internet routing within a cluster of
17 networks.
18 In normal operation routed listens on the udp(4) socket for the route
20 service (see services(5)) for routing information packets. If the host
21 is an internetwork router, it periodically supplies copies of its rout‐
22 ing tables to any directly connected hosts and networks.
23 When routed is started, it uses the SIOCGIFCONF ioctl to find those
25 directly connected interfaces configured into the system and marked
26 ``up'' (the software loopback interface is ignored). If multiple
27 interfaces are present, it is assumed that the host will forward pack‐
28 ets between networks. Routed then transmits a request packet on each
29 interface (using a broadcast packet if the interface supports it) and
30 enters a loop, listening for request and response packets from other
31 hosts.
32 When a request packet is received, routed formulates a reply based on
34 the information maintained in its internal tables. The response packet
35 generated contains a list of known routes, each marked with a ``hop
36 count'' metric (a count of 16, or greater, is considered ``infinite'').
37 The metric associated with each route returned provides a metric rela‐
38 tive to the sender.
39 Response packets received by routed are used to update the routing
41 tables if one of the following conditions is satisfied:
42 (1) No routing table entry exists for the destination network or
44 host, and the metric indicates the destination is ``reachable''
45 (i.e. the hop count is not infinite).
46 (2) The source host of the packet is the same as the router in the
48 existing routing table entry. That is, updated information is
49 being received from the very internetwork router through which
50 packets for the destination are being routed.
51 (3) The existing entry in the routing table has not been updated for
53 some time (defined to be 90 seconds) and the route is at least
54 as cost effective as the current route.
55 (4) The new route describes a shorter route to the destination than
57 the one currently stored in the routing tables; the metric of
58 the new route is compared against the one stored in the table to
59 decide this.
60 When an update is applied, routed records the change in its internal
62 tables and updates the kernel routing table. The change is reflected
63 in the next response packet sent