| 1 | .\" Copyright (c) 1983 Regents of the University of California. |
| 2 | .\" All rights reserved. The Berkeley software License Agreement |
| 3 | .\" specifies the terms and conditions for redistribution. |
| 4 | .\" |
| 5 | .\" @(#)routed.8 6.3 (Berkeley) %G% |
| 6 | .\" |
| 7 | .TH ROUTED 8C "" |
| 8 | .UC 5 |
| 9 | .SH NAME |
| 10 | routed \- network routing daemon |
| 11 | .SH SYNOPSIS |
| 12 | .B /etc/routed |
| 13 | [ |
| 14 | .B \-d |
| 15 | ] [ |
| 16 | .B \-g |
| 17 | ] [ |
| 18 | .B \-s |
| 19 | ] [ |
| 20 | .B \-q |
| 21 | ] [ |
| 22 | .B \-t |
| 23 | ] [ |
| 24 | .I logfile |
| 25 | ] |
| 26 | .SH DESCRIPTION |
| 27 | .I Routed |
| 28 | is invoked at boot time to manage the network routing tables. |
| 29 | The routing daemon uses a variant of the Xerox NS Routing |
| 30 | Information Protocol in maintaining up to date kernel routing |
| 31 | table entries. |
| 32 | It used a generalized protocol capable of use with multiple |
| 33 | address types, but is currently used only for Internet routing |
| 34 | within a cluster of networks. |
| 35 | .PP |
| 36 | In normal operation |
| 37 | .I routed |
| 38 | listens on the |
| 39 | .IR udp (4P) |
| 40 | socket for the |
| 41 | .I route |
| 42 | service (see |
| 43 | .IR services (5)) |
| 44 | for routing information packets. If the host is an |
| 45 | internetwork router, it periodically supplies copies |
| 46 | of its routing tables to any directly connected hosts |
| 47 | and networks. |
| 48 | .PP |
| 49 | When |
| 50 | .I routed |
| 51 | is started, it uses the SIOCGIFCONF |
| 52 | .I ioctl |
| 53 | to find those |
| 54 | directly connected interfaces configured into the |
| 55 | system and marked ``up'' (the software loopback interface |
| 56 | is ignored). If multiple interfaces |
| 57 | are present, it is assumed that the host will forward packets |
| 58 | between networks. |
| 59 | .I Routed |
| 60 | then transmits a |
| 61 | .I request |
| 62 | packet on each interface (using a broadcast packet if |
| 63 | the interface supports it) and enters a loop, listening |
| 64 | for |
| 65 | .I request |
| 66 | and |
| 67 | .I response |
| 68 | packets from other hosts. |
| 69 | .PP |
| 70 | When a |
| 71 | .I request |
| 72 | packet is received, |
| 73 | .I routed |
| 74 | formulates a reply based on the information maintained in its |
| 75 | internal tables. The |
| 76 | .I response |
| 77 | packet generated contains a list of known routes, each marked |
| 78 | with a ``hop count'' metric (a count of 16, or greater, is |
| 79 | considered ``infinite''). The metric associated with each |
| 80 | route returned provides a metric |
| 81 | .IR "relative to the sender" . |
| 82 | .PP |
| 83 | .I Response |
| 84 | packets received by |
| 85 | .I routed |
| 86 | are used to update the routing tables if one of the following |
| 87 | conditions is satisfied: |
| 88 | .TP |
| 89 | (1) |
| 90 | No routing table entry exists for the destination network |
| 91 | or host, and the metric indicates the destination is ``reachable'' |
| 92 | (i.e. the hop count is not infinite). |
| 93 | .TP |
| 94 | (2) |
| 95 | The source host of the packet is the same as the router in the |
| 96 | existing routing table entry. That is, updated information is |
| 97 | being received from the very internetwork router through which |
| 98 | packets for the destination are being routed. |
| 99 | .TP |
| 100 | (3) |
| 101 | The existing entry in the routing table has not been updated for |
| 102 | some time (defined to be 90 seconds) and the route is at least |
| 103 | as cost effective as the current route. |
| 104 | .TP |
| 105 | (4) |
| 106 | The new route describes a shorter route to the destination than |
| 107 | the one currently stored in the routing tables; the metric of |
| 108 | the new route is compared against the one stored in the table |
| 109 | to decide this. |
| 110 | .PP |
| 111 | When an update is applied, |
| 112 | .I routed |
| 113 | records the change in its internal tables and updates the kernel |
| 114 | routing table. |
| 115 | The change is reflected in the next |
| 116 | .I response |
| 117 | packet sent. |
| 118 | .PP |
| 119 | In addition to processing incoming packets, |
| 120 | .I routed |
| 121 | also periodically checks the routing table entries. |
| 122 | If an entry has not been updated for 3 minutes, the entry's metric |
| 123 | is set to infinity and marked for deletion. Deletions are delayed |
| 124 | an additional 60 seconds to insure the invalidation is propagated |
| 125 | throughout the local internet. |
| 126 | .PP |
| 127 | Hosts acting as internetwork routers gratuitously supply their |
| 128 | routing tables every 30 seconds to all directly connected hosts |
| 129 | and networks. |
| 130 | The response is sent to the broadcast address on nets capable of that function, |
| 131 | to the destination address on point-to-point links, and to the router's |
| 132 | own address on other networks. |
| 133 | The normal routing tables are bypassed when sending gratuitous responses. |
| 134 | The reception of responses on each network is used to determine that the |
| 135 | network and interface are functioning correctly. |
| 136 | If no response is received on an interface, another route may be chosen |
| 137 | to route around the interface, or the route may be dropped if no alternative |
| 138 | is available. |
| 139 | .PP |
| 140 | .I Routed supports several options: |
| 141 | .TP |
| 142 | .B \-d |
| 143 | Enable additional debugging information to be logged, |
| 144 | such as bad packets received. |
| 145 | .TP |
| 146 | .B \-g |
| 147 | This flag is used on internetwork routers to offer a route |
| 148 | to the ``default'' destination. |
| 149 | This is typically used on a gateway to the Internet, |
| 150 | or on a gateway that uses another routing protocol whose routes |
| 151 | are not reported to other local routers. |
| 152 | .TP |
| 153 | .B \-s |
| 154 | Supplying this |
| 155 | option forces |
| 156 | .I routed |
| 157 | to supply routing information whether it is acting as an internetwork |
| 158 | router or not. |
| 159 | This is the default if multiple network interfaces are present, |
| 160 | or if a point-to-point link is in use. |
| 161 | .TP |
| 162 | .B \-q |
| 163 | This |
| 164 | is the opposite of the |
| 165 | .B \-s |
| 166 | option. |
| 167 | .TP |
| 168 | .B \-t |
| 169 | If the |
| 170 | .B \-t |
| 171 | option is specified, all packets sent or received are |
| 172 | printed on the standard output. In addition, |
| 173 | .I routed |
| 174 | will not divorce itself from the controlling terminal |
| 175 | so that interrupts from the keyboard will kill the process. |
| 176 | .PP |
| 177 | Any other argument supplied is interpreted as the name |
| 178 | of file in which |
| 179 | .IR routed 's |
| 180 | actions should be logged. This log contains information |
| 181 | about any changes to the routing tables and, if not tracing all packets, |
| 182 | a history of recent messages sent and received which are related to |
| 183 | the changed route. |
| 184 | .PP |
| 185 | In addition to the facilities described above, |
| 186 | .I routed |
| 187 | supports the notion of ``distant'' |
| 188 | .I passive |
| 189 | and |
| 190 | .I active |
| 191 | gateways. When |
| 192 | .I routed |
| 193 | is started up, it reads the file |
| 194 | .I /etc/gateways |
| 195 | to find gateways which may not be located using |
| 196 | only information from the SIOGIFCONF |
| 197 | .IR ioctl . |
| 198 | Gateways specified in this manner should be marked passive |
| 199 | if they are not expected to exchange routing information, |
| 200 | while gateways marked active |
| 201 | should be willing to exchange routing information (i.e. |
| 202 | they should have a |
| 203 | .I routed |
| 204 | process running on the machine). |
| 205 | Routes through passive gateways are installed in the |
| 206 | kernel's routing tables once upon startup. |
| 207 | Such routes are not included in |
| 208 | any routing information transmitted. |
| 209 | Active gateways are treated equally to network |
| 210 | interfaces. Routing information is distributed |
| 211 | to the gateway and if no routing information is |
| 212 | received for a period of the time, the associated |
| 213 | route is deleted. |
| 214 | Gateways marked |
| 215 | .I external |
| 216 | are also passive, but are not placed in the kernel |
| 217 | routing table nor are they included in routing updates. |
| 218 | The function of external entries is to inform |
| 219 | .I routed |
| 220 | that another routing process |
| 221 | will install such a route, and that alternate routes to that destination |
| 222 | should not be installed. |
| 223 | Such entries are only required when both routers may learn of routes |
| 224 | to the same destination. |
| 225 | .PP |
| 226 | The |
| 227 | .I /etc/gateways |
| 228 | is comprised of a series of lines, each in |
| 229 | the following format: |
| 230 | .PP |
| 231 | .nf |
| 232 | < \fBnet\fP | \fBhost\fP > \fIname1\fP \fBgateway\fP \fIname2\fP \fBmetric\fP \fIvalue\fP < \fBpassive\fP | \fBactive\fP | \fBexternal\fP > |
| 233 | .fi |
| 234 | .PP |
| 235 | The |
| 236 | .B net |
| 237 | or |
| 238 | .B host |
| 239 | keyword indicates if the route is to a network or specific host. |
| 240 | .PP |
| 241 | .I Name1 |
| 242 | is the name of the destination network or host. This may be a |
| 243 | symbolic name located in |
| 244 | .I /etc/networks |
| 245 | or |
| 246 | .I /etc/hosts |
| 247 | (or, if started after |
| 248 | .IR named (8), |
| 249 | known to the name server), |
| 250 | or an Internet address specified in ``dot'' notation; see |
| 251 | .IR inet (3N). |
| 252 | .PP |
| 253 | .I Name2 |
| 254 | is the name or address of the gateway to which messages should |
| 255 | be forwarded. |
| 256 | .PP |
| 257 | .I Value |
| 258 | is a metric indicating the hop count to the destination host |
| 259 | or network. |
| 260 | .PP |
| 261 | One of the keywords |
| 262 | .BR passive , |
| 263 | .B active |
| 264 | or |
| 265 | .B external |
| 266 | indicates if the gateway should be treated as |
| 267 | .I passive |
| 268 | or |
| 269 | .I active |
| 270 | (as described above), |
| 271 | or whether the gateway is |
| 272 | .I external |
| 273 | to the scope of the |
| 274 | .I routed |
| 275 | protocol. |
| 276 | .PP |
| 277 | Internetwork routers that are directly attached to the Arpanet or Milnet |
| 278 | should use the Exterior Gateway Protocol (EGP) to gather routing information |
| 279 | rather then using a static routing table of passive gateways. |
| 280 | EGP is required in order to provide routes for local networks to the rest |
| 281 | of the Internet system. |
| 282 | Sites needing assistance with such configurations |
| 283 | should contact the Computer Systems Research Group at Berkeley. |
| 284 | .SH FILES |
| 285 | .DT |
| 286 | /etc/gateways for distant gateways |
| 287 | .SH "SEE ALSO" |
| 288 | ``Internet Transport Protocols'', XSIS 028112, Xerox System Integration |
| 289 | Standard. |
| 290 | .br |
| 291 | udp(4P), icmp(4P), XNSrouted(8C), htable(8) |
| 292 | .SH BUGS |
| 293 | The kernel's routing tables may not correspond to those of |
| 294 | .I routed |
| 295 | when redirects change or add routes. |
| 296 | .I Routed |
| 297 | should note any redirects received by reading |
| 298 | the ICMP packets received via a raw socket. |
| 299 | .PP |
| 300 | .I Routed |
| 301 | should incorporate other routing protocols, |
| 302 | such as Xerox NS |
| 303 | .RI ( XNSrouted (8C)) |
| 304 | and EGP. |
| 305 | Using separate processes for each requires configuration options |
| 306 | to avoid redundant or competing routes. |
| 307 | .PP |
| 308 | .I Routed |
| 309 | should listen to intelligent interfaces, such as an IMP, |
| 310 | to gather more information. |
| 311 | It does not always detect unidirectional failures in network interfaces |
| 312 | (e.g., when the output side fails). |