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To terminate a SLIP connection, follow these steps:
$ TCPIP SET NOINTERFACE interface |
See Section A.10.
Routing allows traffic from your local network to reach its destination elsewhere on the internet. All hosts and gateways on a network use routing protocols to exchange and store routing information. Routing is the act of forwarding datagrams based on information stored in a routing table.
The DIGITAL TCP/IP Services for OpenVMS product provides two types of
routing: static and dynamic. This chapter reviews key routing concepts
and describes how to configure static or dynamic routing on your system.
4.1 Reviewing Key Concepts
If the hosts on your network need to communicate with computers on other networks, a route through a gateway must be defined. All hosts and gateways on a network store information about routes in routing tables. With DIGITAL TCP/IP Services for OpenVMS, routing tables are maintained in both dynamic and permanent memory.
You can define routes manually (static routing) or you can enable
routing protocols that exchange information and build routing tables
based on the information exchanged (dynamic routing).
4.1.1 Static Routing
Because static routing requires manual configuration, it is most useful
when the number of gateways is limited and where routes do not change
frequently. For information on manually configuring routing, see
Section 4.2.
4.1.2 Dynamic Routing
Complex environments require a more flexible approach to routing than a static routing table provides. Routing protocols distribute information that reflect changing network conditions and update the routing table accordingly. Routing protocols can switch to a backup route when a primary route becomes unavailable and can determine the best route to a given destination.
Dynamic routing tables use information received by means of routing protocol updates; when routes change, the routing protocol provides information on the changes.
Routing daemons implement a routing policy, that is, the set of rules that decide which routes go into the routing table. A routing daemon writes routing messages to a routing socket causing the kernel to add a new route, delete an existing route, or modify an existing route.
The kernel also generates routing messages that can be read by any routing socket when events occur that may be of interest to the process, for example, the interface has gone down or a redirect has been received.
DIGITAL TCP/IP Services for OpenVMS implements two routing daemons: the
Routing Daemon (ROUTED) and the Gateway Routing Daemon (GATED). The
following sections provide more information.
4.1.2.1 Routing Daemon (ROUTED)
This daemon (pronounced route-de) supports the Routing Information Protocol (RIP). When ROUTED starts, it issues routing update requests then listens for responses. A system configured to supply RIP information responds to the request with an update packet. The update packet contains destination addresses and routing metrics associated with each destination. After receiving a RIP update, the ROUTED uses the information to update its routing table.
To configure dynamic routing with ROUTED, see Section 4.3.
4.1.2.2 Gateway Routing Daemon (GATED)
This daemon (pronounced gate-de) supports interior and exterior gateway protocols. It obtains information from several routing protocols and selects the best routes based on that information. You can configure GATED to use one or more of the protocols described in Table 4-1.
| Protocol | RFC | Description |
|---|---|---|
| Routing Information Protocol (RIP) Versions 1 and 2 | RFC 1058, RFC 1388 | RIP is a commonly used interior protocol that selects the route with the lowest metric (hop count) as the best route. |
| Open Shortest Path First (OSPF) Version 2 | RFC 1583 | Another interior routing protocol, OSPF is a link-state protocol (shortest path first) and better suited than RIP for use in complex networks with many routers. |
| Exterior Gateway Protocol (EGP) | RFC 904 | EGP exchanges reachability information between autonomous systems. An autonomous system is usually defined as a set of routers under a single administration, using an interior gateway protocol and common metric to route packets. Autonomous systems use exterior routing protocols to route packets to other autonomous systems. |
| Border Gateway Protocol (BGP) | RFCs 1163, 1267, 1654 | Like EGP, BGP exchanges reachability information between autonomous systems but supports nonhierarchical topologies. BGP uses path attributes to provide more information about each route. Path attributes can include, for example, administrative preferences based on political, organizational, or security considerations. |
| Router Discovery | RFC 1256 | This protocol is used to inform hosts of the availability of hosts it can send packets to and to supplement a statically configured default router. |
These routing protocols are configured in the GATED configuration file TCPIP$GATED.CONF. This file contains statements that control tracing options, select routing protocols, manage routing information, and manage independent system routing.
For information on configuring dynamic routing with GATED, see
Section 4.4.
4.2 Configuring Static Routes
The first time you run the configuration procedure, TCPIP$CONFIG.COM, static routing is configured automatically. To manually configure static routing, use the CREATE ROUTE command to create an empty routes database file.
The default file name is SYS$COMMON:[SYSEXE]TCPIP$ROUTE.DAT. To specify a different name, define the systemwide logical name TCPIP$ROUTE.
Do not execute the CREATE ROUTE command unless you intend to reconfigure your entire cluster. |
To create a static route, use the SET ROUTE command. The command has the following effects:
The command requires the following information:
Compaq strongly recommends that you do not specify alias names with the destination parameter or the /GATEWAY=host qualifier.
To define a route to any host on a specific network, enter:
TCPIP> SET ROUTE network_IP_address /GATEWAY="gateway" /NETWORK |
To define a route to a specific host on a specific network, enter:
TCPIP> SET ROUTE remote_host /GATEWAY="gateway" |
Example 1:
In the following example, the network is active. The SET ROUTE command
adds a route to the volatile routes database. TCPIP starts directing
communication for flamingo through gateway francolin.
TCPIP> SET ROUTE "flamingo" /GATEWAY="francolin" |
Example 2:
In the following example, the network is active. The SET ROUTE command
defines a routing path in the volatile routes database. The command
specifies that traffic for the network with IP address 128.30.0.0 use
gateway francolin.
TCPIP> SET ROUTE 128.30.0.0 /NETWORK /GATEWAY="francolin" |
Example 3:
In the following example, the network is not active. The SET ROUTE
command adds the new route to the permanent routes database. The next
time the product starts up, packets for NENE will go through a gateway
called bird.of.paradise.
TCPIP> SET ROUTE NENE /GATEWAY="bird.of.paradise" |
At startup, the information in the permanent routes database, if any exists, is loaded into the volatile routes database. You can add permanent routes while the product is stopped or while it is running. If it is running, use the /PERMANENT qualifier.
Example 4:
The following command permanently sets routing for host
albatross to go through gateway birdygate.
TCPIP> SET ROUTE "albatross" /GATEWAY="birdygate" /PERMANENT |
A default route is a route used to direct data that is addressed to an unidentifiable network address. To define a default route, use the /DEFAULT qualifier.
Example 5:
The following command sets a default route. NIGHTINGALE is the default
gateway.
TCPIP> SET ROUTE /DEFAULT /GATEWAY=NIGHTINGALE |
To check that your routes are set up correctly, use either the LOOP or
PING command.
4.2.0.2 Displaying Manually Defined Routes
To display static routes, use the SHOW ROUTE command. To see the permanent database, specify the /PERMANENT qualifier.
The display shows the following types of routes:
To display a route that was defined by address, specify either its address or a wildcard.
Example 1:
The following example displays information about all the manually
defined routes.
TCPIP> SHOW ROUTE /FULL
DYNAMIC database
Type Destination Gateway
AN 11.111.0.0 destin_host1 11.110.5.118 gate_host
AH 22.111.4.10 destin_host2 22.110.5.120 gate_host_2
|
Example 2:
The following example displays the permanent static routes that were
defined with SET ROUTE /PERMANENT.
TCPIP> SHOW ROUTE /PERMANENT
PERMANENT
Type Destination Gateway
PN 0.0.0.0 11.20.208.100 pterodactyl.extinct.com
PN 1.1.1.1 22.2.2.2
|
Use the configuration procedure TCPIP$CONFIG to enable dynamic routing and configure your host to receive routing protocol messages as follows:
To disable dynamic routing:
When you disable GATED routing, the GATED routes are preserved. To
disable GATED and remove all GATED routes from the routing table, enter
the command STOP ROUTING/GATED.
4.4 Configuring GATED
You must configure the GATED protocols before enabling GATED routing. Edit a copy of the sample file TCPIP$GATED.TEMPLATE (located in SYS$SYSDEVICE:[TCPIP$GATED]) to add statements that select routing protocols, manage routing information, manage independent system routing, and control tracing options.
After editing this file, save it to TCPIP$GATED.CONF, in SYS$SYSDEVICE:[TCPIP$GATED], and use TCPIP$CONFIG to enable GATED. If GATED is already running, you must stop it by entering the command STOP ROUTING/GATED then restart GATED (enter START ROUTING/GATED.)
If you do not format the configuration file correctly, GATED will terminate.
See DIGITAL TCP/IP Services for OpenVMS Management Command Reference for detailed descriptions of the SET GATED and START
ROUTING/GATED commands.
4.4.1 Sample GATED Configuation File
A sample GATED configuration file follows. For a description of valid statements, statement syntax, and sample protocol configurations, see Appendix B.
#---------------------------------------------------------------------
#
# Copyright (c) Digital Equipment Corporation, 1998
#
# TCPIP$GATED.CONF - Sample gateway routing daemon (GATED)
# configuration file, preconfigured for RIP v1.
#
# This file contains information that is read by the GATED daemon at
# initialization time. This file contains statements that
#
# o Control tracing options
# o Select routing protocols
# o Manage routing information
# o Manage idependent system routing
#
# See the DIGITAL TCP/IP Services for OpenVMS Management guide for
# instructions on using this file.
#
#____________________________________________________________________
interfaces {
interface all passive ;
};
#
# Protocols:
#
rip on {
broadcast;
interface all ripin ripout version 1;
};
#
redirect on;
routerdiscovery server off;
hello off;
ospf off;
egp off;
bgp off;
snmp off;
#
# Static routes:
#
#static {
# 10.1.2.0 mask 255.255.255.0 gateway 10.1.1.1;
# default gateway 10.1.2.3;
# };
#
# Policy:
#
#export proto rip {
# proto static { all metric 1; };
# proto direct { all; };
# proto rip { all; };
# };
|
By default, the startup procedure automatically sets IP forwarding.
To manually configure your system as an internet gateway, enter the following commands:
TCPIP> SET PROTOCOL IP /FORWARD |
TCPIP> SET CONFIGURATION PROTOCOL IP /FORWARD |
Identify the gateway for each client. For instructions, see the client's product documentation.
To disable the gateway function interactively, enter:
TCPIP> SET PROTOCOL IP /NOFORWARD |
To disable the gateway at TCP/IP Services startup, type:
TCPIP> SET CONFIGURATION PROTOCOL IP /NOFORWARD |
Reassembly is the process of reconstructing a complete data message from received fragments. The reassembly timer determines the length of time allowed for the reassembly process. You can modify the reassembly timer to ensure that IP datagram fragments are optimally reassembled at the destination host.
Consider the following when setting the reassembly timer:
Enter the following commands to reset the reassembly timer:
TCPIP> SET PROTOCOL IP /REASSEMBLY_TIMER=n |
TCPIP> SET CONFIGURATION PROTOCOL IP /REASSEMBLY_TIMER=n |
In the following example, the first command changes the IP reassembly time to 20 seconds on the running system. This new setting remains in effect until the next TCP/IP Services startup.
The second command makes the change permanent by modifying the configuration database, TCPIP$CONFIGURATION.DAT.
TCPIP> SET PROTOCOL IP /REASSEMBLY_TIMER=20 TCPIP> SET CONFIGURATION PROTOCOL IP /REASSEMBLY_TIMER=20 |
Subnetwork routing, also called subnetting, lets you extend the IP addressing scheme by organizing hosts within a network into logical groups. A network can be made up of several subnetworks.
If a gateway connects these networks, a host on another network can access a host on a subnetwork. Data from the host on the other network is routed as follows:
Subnetwork routing lets one network address span multiple physical networks. You can use local gateways and subnetwork addresses to each local physical network to make your network appear as one network to other systems.
For example, a company has one assigned IP address, even though it has several physical networks. Using local gateways, the network manager assigns a subnetwork address to each local physical network. This makes the company appear to have only one network to outside systems.
Subnetwork routing also works in the reverse. You can create multiple
subnetworks (logical groups) on the same physical network. Use a
network interface as a gateway between the multiple subnetworks.
Setting up multiple subnets on one physical network has one
disadvantage. Because the subnetworks are on the same broadcast medium,
they receive broadcasts destined for other subnetworks, and these
broadcasts must be discarded, except on the gateway.
4.6.1 Extending Subnetwork Routing
To use extended subnetwork routing, define pseudo-interfaces. A pseudo-interface is a data structure that extends subnetwork routing. The name of an internet pseudo-interface has the following characteristics:
| A | Controller 0 |
| B | Controller 1 |
| C | Controller 2 |
For example, for an OpenVMS Alpha system with two Ethernet controllers --- EZA0 and EZB0 --- you can define the following internet interfaces and pseudo-interfaces:
To extend subnetwork routing, follow these steps:
TCPIP> SET NOINTERFACE interface TCPIP> SET INTERFACE interface /HOST=host - _TCPIP> /NETWORK_MASK=mask /BROADCAST_MASK=b_mask TCPIP> SET CONFIGURATION INTERFACE interface /HOST=host - _TCPIP> /NETWORK_MASK=mask /BROADCAST_MASK=b_mask |
TCPIP> SET NOINTERFACE FFA0 TCPIP> SET INTERFACE FFA0 /HOST=KESTREL /NETWORK_MASK=255.255.0.0 - _TCPIP> /BROADCAST_MASK=128.30.0.0 |
TCPIP> SET CONFIGURATION INTERFACE FFA0 /HOST=KESTREL - _TCPIP> /NETWORK_MASK=255.255.0.0 /BROADCAST_MASK=128.30.0.0 |
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