|IN.ROUTED(8)||Maintenance Commands and Procedures||IN.ROUTED(8)|
/usr/sbin/in.routed [-AdghmnqsStVz] [-T tracefile [-v]] [-F net[/mask ][,metric]] [-P params]
in.routed is managed by means of the service management facility (SMF), using the fault management resource identifier (FMRI):
The daemon listens on a udp socket for the route service (see services(5)) for Routing Information Protocol packets. It also sends and receives multicast Router Discovery ICMP messages. If the host is a router, in.routed periodically supplies copies of its routing tables to any directly connected hosts and networks. It also advertises or solicits default routes using Router Discovery ICMP messages.
When started (or when a network interface is later turned on), in.routed uses an AF_ROUTE address family facility to find those directly connected interfaces configured into the system and marked "up". It adds necessary routes for the interfaces to the kernel routing table. Soon after being first started, and provided there is at least one interface on which RIP has not been disabled, in.routed deletes all pre-existing non-static routes in the kernel table. Static routes in the kernel table are preserved and included in RIP responses if they have a valid RIP metric (see route(8)).
If more than one interface is present (not counting the loopback interface), it is assumed that the host should forward packets among the connected networks. After transmitting a RIP request and Router Discovery Advertisements or Solicitations on a new interface, the daemon enters a loop, listening for RIP request and response and Router Discovery packets from other hosts.
When a request packet is received, in.routed formulates a reply based on the information maintained in its internal tables. The response packet generated contains a list of known routes, each marked with a "hop count" metric (a count of 16 or greater is considered "infinite"). Advertised metrics reflect the metric associated with an interface (see ifconfig(8)), so setting the metric on an interface is an effective way to steer traffic.
Responses do not include routes with a first hop on the requesting network, to implement in part split-horizon. Requests from query programs such as rtquery(8) are answered with the complete table.
The routing table maintained by the daemon includes space for several gateways for each destination to speed recovery from a failing router. RIP response packets received are used to update the routing tables, provided they are from one of the several currently recognized gateways or advertise a better metric than at least one of the existing gateways.
When an update is applied, in.routed records the change in its own tables and updates the kernel routing table if the best route to the destination changes. The change in the kernel routing table is reflected in the next batch of response packets sent. If the next response is not scheduled for a while, a flash update response containing only recently changed routes is sent.
In addition to processing incoming packets, in.routed also periodically checks the routing table entries. If an entry has not been updated for 3 minutes, the entry's metric is set to infinity and marked for deletion. Deletions are delayed until the route has been advertised with an infinite metric to insure the invalidation is propagated throughout the local internet. This is a form of poison reverse.
Routes in the kernel table that are added or changed as a result of ICMP Redirect messages are deleted after a while to minimize black-holes. When a TCP connection suffers a timeout, the kernel tells in.routed, which deletes all redirected routes through the gateway involved, advances the age of all RIP routes through the gateway to allow an alternate to be chosen, and advances of the age of any relevant Router Discovery Protocol default routes.
Hosts acting as internetwork routers gratuitously supply their routing tables every 30 seconds to all directly connected hosts and networks. These RIP responses are sent to the broadcast address on nets that support broadcasting, to the destination address on point-to-point links, and to the router's own address on other networks. If RIPv2 is enabled, multicast packets are sent on interfaces that support multicasting.
If no response is received on a remote interface, if there are errors while sending responses, or if there are more errors than input or output (see netstat(8)), then the cable or some other part of the interface is assumed to be disconnected or broken, and routes are adjusted appropriately.
The Internet Router Discovery Protocol is handled similarly. When the daemon is supplying RIP routes, it also listens for Router Discovery Solicitations and sends Advertisements. When it is quiet and listening to other RIP routers, it sends Solicitations and listens for Advertisements. If it receives a good Advertisement and it is not multi-homed, it stops listening for broadcast or multicast RIP responses. It tracks several advertising routers to speed recovery when the currently chosen router dies. If all discovered routers disappear, the daemon resumes listening to RIP responses. It continues listening to RIP while using Router Discovery if multi-homed to ensure all interfaces are used.
The Router Discovery standard requires that advertisements have a default "lifetime" of 30 minutes. That means should something happen, a client can be without a good route for 30 minutes. It is a good idea to reduce the default to 45 seconds using -P rdisc_interval=45 on the command line or rdisc_interval=45 in the /etc/gateways file. See gateways(5).
While using Router Discovery (which happens by default when the system has a single network interface and a Router Discover Advertisement is received), there is a single default route and a variable number of redirected host routes in the kernel table. On a host with more than one network interface, this default route will be via only one of the interfaces. Thus, multi-homed hosts running with -q might need the no_rdisc argument described below.
To support "legacy" systems that can handle neither RIPv2 nor Router Discovery, you can use the pm_rdisc parameter in the /etc/gateways. See gateways(5).
By default, neither Router Discovery advertisements nor solicitations are sent over point-to-point links (for example, PPP). The Solaris OE uses a netmask of all ones (255.255.255.255) on point-to-point links.
in.routed supports the notion of "distant" passive or active gateways. When the daemon is started, it reads the file /etc/gateways to find such distant gateways that cannot be located using only information from a routing socket, to discover if some of the local gateways are passive, and to obtain other parameters. Gateways specified in this manner should be marked passive if they are not expected to exchange routing information, while gateways marked active should be willing to exchange RIP packets. Routes through passive gateways are installed in the kernel's routing tables once upon startup and are not included in transmitted RIP responses.
Distant active gateways are treated like network interfaces. RIP responses are sent to the distant active gateway. If no responses are received, the associated route is deleted from the kernel table and RIP responses are advertised via other interfaces. If the distant gateway resumes sending RIP responses, the associated route is restored.
Distant active gateways can be useful on media that do not support broadcasts or multicasts but otherwise act like classic shared media, such as some ATM networks. One can list all RIP routers reachable on the HIPPI or ATM network in /etc/gateways with a series of "host" lines. Note that it is usually desirable to use RIPv2 in such situations to avoid generating lists of inferred host routes.
Gateways marked external are also passive, but are not placed in the kernel routing table, nor are they included in routing updates. The function of external entries is to indicate that another routing process will install such a route if necessary, and that other routes to that destination should not be installed by in.routed. Such entries are required only when both routers might learn of routes to the same destination.
# routeadm -m route:default name=value
Internet Transport Protocols, XSIS 028112, Xerox System Integration Standard
Routing Information Protocol, v2 (RFC 2453, STD 0056, November 1998)
RIP-v2 MD5 Authentication (RFC 2082, January 1997)
Routing Information Protocol, v1 (RFC 1058, June 1988)
ICMP Router Discovery Messages (RFC 1256, September 1991)
in.routed does not always detect unidirectional failures in network interfaces, for example, when the output side fails.
|March 30, 2022||OmniOS|