1.\" Copyright (c) 1983, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" %sccs.include.redist.man% 5.\" 6.\" @(#)routed.8 8.1 (Berkeley) 06/05/93 7.\" 8.Dd 9.Dt ROUTED 8 10.Os BSD 4.2 11.Sh NAME 12.Nm routed 13.Nd network routing daemon 14.Sh SYNOPSIS 15.Nm routed 16.Op Fl d 17.Op Fl g 18.Op Fl q 19.Op Fl s 20.Op Fl t 21.Op Ar logfile 22.Sh DESCRIPTION 23.Nm Routed 24is invoked at boot time to manage the network routing tables. 25The routing daemon uses a variant of the Xerox NS Routing 26Information Protocol in maintaining up to date kernel routing 27table entries. 28It used a generalized protocol capable of use with multiple 29address types, but is currently used only for Internet routing 30within a cluster of networks. 31.Pp 32In normal operation 33.Nm routed 34listens on the 35.Xr udp 4 36socket for the 37.Xr route 8 38service (see 39.Xr services 5 ) 40for routing information packets. If the host is an 41internetwork router, it periodically supplies copies 42of its routing tables to any directly connected hosts 43and networks. 44.Pp 45When 46.Nm routed 47is started, it uses the 48.Dv SIOCGIFCONF 49.Xr ioctl 2 50to find those 51directly connected interfaces configured into the 52system and marked ``up'' (the software loopback interface 53is ignored). If multiple interfaces 54are present, it is assumed that the host will forward packets 55between networks. 56.Nm Routed 57then transmits a 58.Em request 59packet on each interface (using a broadcast packet if 60the interface supports it) and enters a loop, listening 61for 62.Em request 63and 64.Em response 65packets from other hosts. 66.Pp 67When a 68.Em request 69packet is received, 70.Nm routed 71formulates a reply based on the information maintained in its 72internal tables. The 73.Em response 74packet generated contains a list of known routes, each marked 75with a ``hop count'' metric (a count of 16, or greater, is 76considered ``infinite''). The metric associated with each 77route returned provides a metric 78.Em relative to the sender . 79.Pp 80.Em Response 81packets received by 82.Nm routed 83are used to update the routing tables if one of the following 84conditions is satisfied: 85.Bl -enum 86.It 87No routing table entry exists for the destination network 88or host, and the metric indicates the destination is ``reachable'' 89(i.e. the hop count is not infinite). 90.It 91The source host of the packet is the same as the router in the 92existing routing table entry. That is, updated information is 93being received from the very internetwork router through which 94packets for the destination are being routed. 95.It 96The existing entry in the routing table has not been updated for 97some time (defined to be 90 seconds) and the route is at least 98as cost effective as the current route. 99.It 100The new route describes a shorter route to the destination than 101the one currently stored in the routing tables; the metric of 102the new route is compared against the one stored in the table 103to decide this. 104.El 105.Pp 106When an update is applied, 107.Nm routed 108records the change in its internal tables and updates the kernel 109routing table. 110The change is reflected in the next 111.Em response 112packet sent. 113.Pp 114In addition to processing incoming packets, 115.Nm routed 116also periodically checks the routing table entries. 117If an entry has not been updated for 3 minutes, the entry's metric 118is set to infinity and marked for deletion. Deletions are delayed 119an additional 60 seconds to insure the invalidation is propagated 120throughout the local internet. 121.Pp 122Hosts acting as internetwork routers gratuitously supply their 123routing tables every 30 seconds to all directly connected hosts 124and networks. 125The response is sent to the broadcast address on nets capable of that function, 126to the destination address on point-to-point links, and to the router's 127own address on other networks. 128The normal routing tables are bypassed when sending gratuitous responses. 129The reception of responses on each network is used to determine that the 130network and interface are functioning correctly. 131If no response is received on an interface, another route may be chosen 132to route around the interface, or the route may be dropped if no alternative 133is available. 134.Pp 135Options supported by 136.Nm routed : 137.Bl -tag -width Ds 138.It Fl d 139Enable additional debugging information to be logged, 140such as bad packets received. 141.It Fl g 142This flag is used on internetwork routers to offer a route 143to the ``default'' destination. 144This is typically used on a gateway to the Internet, 145or on a gateway that uses another routing protocol whose routes 146are not reported to other local routers. 147.It Fl s 148Supplying this 149option forces 150.Nm routed 151to supply routing information whether it is acting as an internetwork 152router or not. 153This is the default if multiple network interfaces are present, 154or if a point-to-point link is in use. 155.It Fl q 156This 157is the opposite of the 158.Fl s 159option. 160.It Fl t 161If the 162.Fl t 163option is specified, all packets sent or received are 164printed on the standard output. In addition, 165.Nm routed 166will not divorce itself from the controlling terminal 167so that interrupts from the keyboard will kill the process. 168.El 169.Pp 170Any other argument supplied is interpreted as the name 171of file in which 172.Nm routed Ns \'s 173actions should be logged. This log contains information 174about any changes to the routing tables and, if not tracing all packets, 175a history of recent messages sent and received which are related to 176the changed route. 177.Pp 178In addition to the facilities described above, 179.Nm routed 180supports the notion of ``distant'' 181.Em passive 182and 183.Em active 184gateways. When 185.Nm routed 186is started up, it reads the file 187.Pa /etc/gateways 188to find gateways which may not be located using 189only information from the 190.Dv SIOGIFCONF 191.Xr ioctl 2 . 192Gateways specified in this manner should be marked passive 193if they are not expected to exchange routing information, 194while gateways marked active 195should be willing to exchange routing information (i.e. 196they should have a 197.Nm routed 198process running on the machine). 199Routes through passive gateways are installed in the 200kernel's routing tables once upon startup. 201Such routes are not included in 202any routing information transmitted. 203Active gateways are treated equally to network 204interfaces. Routing information is distributed 205to the gateway and if no routing information is 206received for a period of the time, the associated 207route is deleted. 208Gateways marked 209.Em external 210are also passive, but are not placed in the kernel 211routing table nor are they included in routing updates. 212The function of external entries is to inform 213.Nm routed 214that another routing process 215will install such a route, and that alternate routes to that destination 216should not be installed. 217Such entries are only required when both routers may learn of routes 218to the same destination. 219.Pp 220The 221.Pa /etc/gateways 222is comprised of a series of lines, each in 223the following format: 224.Bd -ragged 225.Pf < Cm net No \&| 226.Cm host Ns > 227.Ar name1 228.Cm gateway 229.Ar name2 230.Cm metric 231.Ar value 232.Pf < Cm passive No \&| 233.Cm active No \&| 234.Cm external Ns > 235.Ed 236.Pp 237The 238.Cm net 239or 240.Cm host 241keyword indicates if the route is to a network or specific host. 242.Pp 243.Ar Name1 244is the name of the destination network or host. This may be a 245symbolic name located in 246.Pa /etc/networks 247or 248.Pa /etc/hosts 249(or, if started after 250.Xr named 8 , 251known to the name server), 252or an Internet address specified in ``dot'' notation; see 253.Xr inet 3 . 254.Pp 255.Ar Name2 256is the name or address of the gateway to which messages should 257be forwarded. 258.Pp 259.Ar Value 260is a metric indicating the hop count to the destination host 261or network. 262.Pp 263One of the keywords 264.Cm passive , 265.Cm active 266or 267.Cm external 268indicates if the gateway should be treated as 269.Em passive 270or 271.Em active 272(as described above), 273or whether the gateway is 274.Em external 275to the scope of the 276.Nm routed 277protocol. 278.Pp 279Internetwork routers that are directly attached to the Arpanet or Milnet 280should use the Exterior Gateway Protocol 281.Pq Tn EGP 282to gather routing information 283rather then using a static routing table of passive gateways. 284.Tn EGP 285is required in order to provide routes for local networks to the rest 286of the Internet system. 287Sites needing assistance with such configurations 288should contact the Computer Systems Research Group at Berkeley. 289.Sh FILES 290.Bl -tag -width /etc/gateways -compact 291.It Pa /etc/gateways 292for distant gateways 293.El 294.Sh SEE ALSO 295.Xr udp 4 , 296.Xr icmp 4 , 297.Xr XNSrouted 8 , 298.Xr htable 8 299.Rs 300.%T Internet Transport Protocols 301.%R XSIS 028112 302.%Q Xerox System Integration Standard 303.Re 304.Sh BUGS 305The kernel's routing tables may not correspond to those of 306.Nm routed 307when redirects change or add routes. 308.Nm Routed 309should note any redirects received by reading 310the 311.Tn ICMP 312packets received via a raw socket. 313.Pp 314.Nm Routed 315should incorporate other routing protocols, 316such as Xerox 317.Tn \&NS 318.Pq Xr XNSrouted 8 319and 320.Tn EGP . 321Using separate processes for each requires configuration options 322to avoid redundant or competing routes. 323.Pp 324.Nm Routed 325should listen to intelligent interfaces, such as an 326.Tn IMP , 327to gather more information. 328It does not always detect unidirectional failures in network interfaces 329(e.g., when the output side fails). 330.Sh HISTORY 331The 332.Nm 333command appeared in 334.Bx 4.2 . 335