Table Of Contents
DECnet Configuration Task List
Enabling DECnet Phase IV Routing
Enabling DECnet Phase IV Prime Routing
Assigning a DECnet Cost to Each Interface
Specifying the DECnet Node Type
Enabling Concurrent Routing and Bridging
Configuring DECnet on Token Rings
Configuring Address Translation
Making a "Poor Man's Routing" Connection
Specifying Name-to-DECnet Address Mapping
Enabling Phase IV-to-Phase V Conversion
Propagating Phase IV VAX Clusters to Phase V Areas
Enabling Phase IV-to-Phase V Conversion
Configuring DECnet Cluster Alias Updates and Setting the DECnet Cluster Holdtime
Propagating Phase IV Areas Through an OSI Backbone
Establishing the Routing Table Size
Setting Maximum Number of Hops
Setting Maximum Number of Hops
Configuring a Static Route for an Interface
Configuring a Default Static Route
Configuring a Default Static Route for an Interface
Configuring DECnet Static Route Propagation
Controlling Access to DECnet Networks
Creating an Access List Based on Source Addresses
Creating an Access List Based on Source and Destination Addresses
Adding Filters to Access Lists
Enabling DECnet Routing on the Router
Setting Maximum Equal-Cost Paths
Establishing Selection for Paths of Equal Cost
Setting the Congestion Threshold
Adjusting the Broadcast Routing Timer
Routing DECnet over ISL in Virtual LANs
Monitoring and Maintaining the DECnet Network
DECnet Phase IV Prime Examples
Phase IV-to-Phase V Conversion Example
Phase IV VAX Cluster Alias to Phase V Areas Example
Phase IV Areas Through an OSI Backbone Example
DECnet Accounting Configuration Example
Configuring DECnet
This chapter describes how to configure our implementation of the DECnet routing protocol. For a complete description of the DECnet commands in this chapter, refer to the "DECnet Commands" chapter of the Cisco IOS Apollo Domain, Banyan VINES, DECnet, ISO CLNS, and XNS Command Reference publication. To locate documentation of other commands that appear in this chapter, use the command reference master index or search online.
To identify the hardware platform or software image information associated with a feature, use the Feature Navigator on Cisco.com to search for information about the feature or refer to the software release notes for a specific release. For more information, see the "Identifying Supported Platforms" section in the "Using Cisco IOS Software" chapter.
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Not all Cisco access servers support the DECnet protocol. For more information, refer to the release notes for the current Cisco IOS release.
DECnet Configuration Task List
To configure DECnet routing, perform the tasks in the following sections:
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See the "DECnet Configuration Examples" section at the end of this chapter for configuration examples.
Enabling DECnet Routing
To enable DECnet routing, perform the tasks in the following sections:
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Enabling DECnet Phase IV Routing
To enable DECnet Phase IV routing, use the following command in global configuration mode:
Router(config)# decnet [network-number] routing decnet-address
Enables the DECnet Phase IV routing protocol on a global basis.
A DECnet host exists as a node in an area. An area spans many routers, and a single interface can have many areas attached to it. Therefore, if a router exists on many cables, it uses the same area and node for itself on all of them. Note how this protocol differs from other routing protocols, where each interface is given a different internetwork address. Figure 9 shows the DECnet approach.
Enabling DECnet changes the MAC addresses of the router interfaces. Changing the MAC addresses is not a problem on routers equipped with nonvolatile memory. On systems that attempt to get their IP network addresses from network servers instead of from nonvolatile memory, there might be a problem with the hardware addresses changing and confusing other IP-speaking hosts. If you are attempting to use DECnet on such a configuration, be sure to set all global DECnet parameters before enabling DECnet routing on the interfaces.
With DECnet Phase IV Prime, the change of MAC addresses is not an issue because you can change the MAC address of the interface.
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Once you have enabled DECnet routing, you can obtain MAC addresses by using the show interfaces EXEC command. To disable DECnet routing, use the no decnet routing command.
Figure 9 DECnet Nodes and Area
Enabling DECnet Phase IV Prime Routing
DECnet Phase IV requires that a MAC station address be constructed using DECnet addressing conventions, with a standard high-order byte string (AA-00-04-00) concatenated with the byte-swapped DECnet node address. Using DECnet addressing conventions can cause problems in configurations in which DECnet nodes must coexist with systems running protocols that have other MAC address restrictions.
DECnet Phase IV Prime allows an arbitrary MAC address on the LAN. An address can be assigned globally (that is, assigned by the IEEE), or it can be assigned locally by a system administrator.
To enable or disable DECnet Phase IV Prime, use one of the following commands in global configuration mode:
Optionally, to map a DECnet multicast address to a Token Ring functional address other than the default functional address, use the following command in interface configuration mode:
For examples of how to enable DECnet Phase IV Prime Routing, see the "DECnet Phase IV Prime Examples" section at the end of this chapter.
Assigning a DECnet Cost to Each Interface
After you have enabled DECnet routing, you must assign a cost to each interface over which you want DECnet to run. Assigning a cost to an interface enables DECnet on the interface and, using a standard formula, assigns a different MAC address than that "burned in" by the manufacturer. This section describes how to assign a cost to each interface.
DECnet routing decisions are based on cost, an arbitrary measure used to compare paths on the internetwork. Costs are based on such measures as hop count or media bandwidth. The lower the cost, the better the path. You must assign a cost to each interface.
To assign a cost to each interface for DECnet Phase IV Prime, use the following command in interface configuration mode:
Most DECnet installations have individualized routing strategies for using costs. Therefore, check the routing strategy used at your installation to ensure that the costs you specify are consistent with those set for other hosts on the network.
Figure 10 shows four routers (three Ethernets) and the various routes linking them. Each link has a different cost associated with it. The least-expensive route from Router 7 to Router 20 is via Router 12.
Figure 10 DECnet Cost Values
Specifying the DECnet Node Type
DECnet routing nodes are referred to as either Level 1 or Level 2 routers. You must specify the node type of the router. A Level 1 router exchanges packets with other end nodes and routers in the same area and ignores Level 2 packets; this type of routing is called intra-area routing. Level 2 routers participate in the DECnet routing protocol with other routers and route packets to and from routers in other areas; this type of routing is called interarea routing. Level 2 routers also act as Level 1 routers in their own area.
The keyword area indicates a Level 2, interarea, router. The keyword routing-iv indicates a Level 1, intra-area router. Level 1, intra-area routing is the default. In Level 1 mode, Cisco IOS software sends packets destined for other areas to a designated interarea router, which forwards them outside the area.
To specify the node types, use one of the following commands in global configuration mode:
For an example of how to configure DECnet, see the "DECnet Example" section at the end of this chapter.
Enabling Concurrent Routing and Bridging
You can route DECnet on some interfaces and transparently bridge it on other interfaces simultaneously. To do this, you must enable concurrent routing and bridging. To configure an interface for concurrent routing and bridging, you use the bridge crb command.
To enable concurrent routing and bridging, use the following command in global configuration mode:
Configuring DECnet on Token Rings
If any Cisco routers are running Release 9.0 or earlier, you can use the Token Ring as a backbone or transit network for DECnet routing but you cannot communicate with non-Cisco DECnet nodes on the Token Ring.
If all Cisco routers are running Release 9.1 or later, you can set DECnet encapsulation to allow Cisco interoperation with non-Cisco equipment.
If you have both Release 9.0 and 9.1 routers in the same network, and you want them to interoperate, you must set the encapsulation type to pre-dec on the Release 9.1 routers.
To run DECnet on Token Ring interfaces, use the following commands in interface configuration mode:
Use the keyword dec with routers running Release 9.1 or later. Use the keyword pre-dec with routers running Release 9.0 or earlier, or in a network where routers running 9.0 and 9.1 must interoperate.
Configuring Address Translation
If you set up multiple networks, we recommend that you configure address translation in order to avoid problems with duplicate addressing between networks. If you have multiple DECnet networks, you must establish an address translation table for selected nodes between networks. Establishing an address translation table eliminates any potential problems of duplicate addressing occurring between networks. The address translation gateway (ATG) allows you to define multiple DECnet networks and map between them.
Mapping Between Networks
Configuring ATG allows Cisco IOS software to route traffic for multiple independent DECnet networks, and to establish a user-specified address translation for selected nodes between networks. Address translation allows connectivity between DECnet networks that might not otherwise be possible because of address conflicts (duplicate addresses) between them. Configuring ATG can be done over all media types.
When you use ATG, all the DECnet configuration commands implicitly apply to network number 0 unless you specify otherwise.
To translate a virtual DECnet address to a real network address, use the following command in global configuration mode:
To display the address mapping information used by the DECnet ATG, use the show decnet map EXEC command.
For a simple example of how to configure address translation, see the "Address Translation Example" section at the end of this chapter.
Making a "Poor Man's Routing" Connection
As an additional feature and security precaution, DECnet "Poor Man's Routing" can be used between nodes outside of the translation map, provided those nodes have access to nodes that are in the map. For example, as illustrated in Figure 11 in the "Address Translation Example" section at the end of this chapter, a user on node B could issue the following VMS operating system command:
$ dir A::D::E::When a Poor Man's Routing connection is made between two networks, only the two adjacent nodes between the networks will have any direct knowledge about the other network. Application-level network access can then be specified to route through the connection.
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Specifying Name-to-DECnet Address Mapping
You can define a name-to-DECnet address mapping, which can be used instead of typing the set of numbers associated with a DECnet address.
To define a name-to-DECnet address mapping, use the following command in global configuration mode:
Router(config)# decnet host name decnet-address
Defines a name-to-DECnet address mapping.
The assigned DECnet name is displayed, where applicable, in the output of the decnet route and show hosts EXEC commands.
Enabling Phase IV-to-Phase V Conversion
Routers that have conversion enabled advertise reachability to both Phase IV and Phase V hosts in both Phase IV and Phase V routing updates. If you have Phase IV hosts in Phase V networks and vice versa, you must enable Phase IV-to-Phase V conversion (and vice versa) in order for all nodes to communicate with each other. To enable DECnet conversion, you must have both DECnet and ISO CLNS configured on your router; then use the following command in global configuration mode:
Router(config)# decnet conversion nsap-prefix
Enables DECnet Phase IV-to-Phase V (and vice versa) conversion on the router.
Verify that the area you specify in the decnet conversion global configuration command is the same as the area you specified in the ISO CLNS address. You must also enable CLNS on all interfaces, even if the router has only Phase IV hosts on some of the interfaces. Enabling CLNS on all interfaces allows information about those routers to be included in link-state packets and, consequently, enables other routers to be informed about the routers connected by that interface.
For an example of how to enable a Phase IV area through an OSI backbone, see the "Phase IV-to-Phase V Conversion Example" section at the end of this chapter.
Propagating Phase IV VAX Clusters to Phase V Areas
A Phase IV VAX cluster comprises one or more VAX machines, each with its own individual node address, and a supplemental node address for the cluster. One VAX machine, known as the gratuitous router, will act as the router for the cluster and advertise the cluster alias as an ISO CLNS end system that is attached to the gratuitous router.
The gratuitous router forms an adjacency with the nearest Phase IV router through the process of exchanging L1 router hellos with this router, similar to the process that Phase IV end systems follow to form an adjacency with Phase IV routers through the exchange of endnode hellos.
The Phase IV router will target the cluster alias specifically looking for the L1 routing updates from the gratuitous router, extracting the cluster alias from the update, and injecting the cluster alias into the Phase V cloud as an ISO CLNS end system. The router will also advertise all routes as being reachable through itself at a cost of 704 and a hop count value of 29, so that the gratuitous router will always attempt to route through the Phase IV router unless it already has a better route. Thus, the Phase IV VAX cluster is made reachable to remote end systems.
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The gratuitous router must form an adjacency with the router that is performing the Phase IV-to Phase-V conversion, therefore, the VAX cluster must be located on the same physical LAN as the Phase IV and Phase V routers.The holdtime for the cluster alias adjacency has a default of 300 seconds and must exceed the VAX broadcast routing timer. To configure the DECnet cluster alias adjacency, use the following command in interface configuration mode:
Router(config-if)# decnet cluster-holdtime
Sets a holdtime for a cluster alias adjacency.
To propagate Phase IV VAX clusters to Phase V areas, perform the tasks in these sections:
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Enabling Phase IV-to-Phase V Conversion
To enable Phase IV-to-Phase V conversion, use the following commands beginning in global configuration mode:
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Router(config)# decnet conversion nsap-prefix
Enables DECnet Phase IV-to-Phase V (and vice versa) conversion on the router.
Configuring CLNS IS-IS
To enable Connetionless Network Service (CLNS) Intermediate System-to-Intermediate System (IS-IS), use the following commands in global configuration mode:
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Router(config)# clns routing
Enables routing of CLNS packets.
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Router(config)# router isis [tag]
Enables IS-IS and enters router configuration mode.
Configuring DECnet Cluster Alias Updates and Setting the DECnet Cluster Holdtime
To configure DECnet cluster alias updates and set the DECnet cluster holdtime, use the following commands beginning in interface configuration mode:
For an example of how to propagate Phase IV VAX clusters to Phase V areas, see the "Phase IV VAX Cluster Alias to Phase V Areas Example" section at the end of this chapter.
Propagating Phase IV Areas Through an OSI Backbone
One limitation of the Phase IV-to-Phase V conversion has been the inability to propagate Phase IV area routes through Open System Interconnection (OSI) clouds. Using the "advertise" feature, you can explicitly configure any DECnet Phase IV areas that you want to propagate outward. You configure the border routers at the Phase IV/Phase V junction.
When distant routers send a packet destined across the cloud to a border router, the router converts the route and sends it as an OSI packet. In order for the converting router to have the corresponding OSI entry in which to convert the Phase IV packet, the other border router at the Phase IV/V junction must inject static discard routes. In this way, the first router converts the packet from Phase IV to Phase V, sending it through the cloud. At the other end, the router advertising the static discard route converts the packet back to Phase IV and discards the Phase V packet. In effect, a false entry is created in the Phase IV area table to propagate this information to other routers. This entry will not overwrite a native Phase IV entry if one already exists in the table.
To enable Phase IV areas to propagate through an OSI backbone on the router, use the following command in global configuration mode:
Router(config)# decnet advertise decnet-area hops cost
Enables DECnet Phase IV areas to propagate through an OSI backbone on the router.
To enable the border router at the far end to convert the Phase V packet back to Phase IV, it must advertise a static discard route. To configure the far border router, use the following command in global configuration mode:
Router(config)# clns route nsap-prefix discard
Advertises a static discard route on the far-end border router.
For an example of how to enable a Phase IV area through an OSI backbone, see the "Phase IV Areas Through an OSI Backbone Example" section at the end of this chapter.
Establishing the Routing Table Size
You can configure the maximum number of addresses and areas allowed in the Cisco IOS software routing table. It is best to keep the number of routing updates small. All areas or nodes that cannot be reached must be advertised as unreachable. When configuring the routing table size, indicate the maximum node and area numbers that can exist in the network. In general, all routers on the network should use the same values for maximum addresses and nodes.
To establish the routing table size, use either or both of the following commands in global configuration mode as needed:
Configuring Level 1 Routers
Perform any of the tasks in the following section for the routers you have configured as Level 1 (intra-area) routers. In Level 1 mode, the router sends packets destined for other areas to a designated interarea router, which forwards them outside the area.
Setting Areas as Unreachable
You can set the maximum cost that Cisco IOS software considers usable for intra-area routing. The software ignores routes within its local area that have a cost greater than the value you specify.
Setting Maximum Number of Hops
You can also set the maximum number of hops (or traversal of different paths) that Cisco IOS software considers usable for intra-area routing. The software ignores routes within its local area that have a value greater than you specify.
To set certain intra-areas as unreachable based on cost value or hop count, use either or both of the following commands in global configuration mode as needed:
Configuring Level 2 Routers
Perform any of the tasks in the following section for the routers you have configured as Level 2 (interarea) routers. In Level 2 mode, Cisco IOS software sends packets destined for other areas via the least-cost path to another interarea router.
Setting Areas as Unreachable
You can set the maximum cost for a usable route to a distant area. Cisco IOS software treats as unreachable any route with a cost greater than the value you specify.
Setting Maximum Number of Hops
You can also set the maximum number of hops for a usable route to a distant area. Cisco IOS software treats as unreachable any route with a hop count greater than the value you specify.
To set certain interareas as unreachable based on cost value or hop count, use either or both of the following commands in global configuration mode as needed:
Specifying Designated Routers
You can determine the router with which all end nodes on an Ethernet communicate if they do not know where else to send a packet. This router is called the designated router and is the router with the highest priority. When two or more routers on a single Ethernet in a single area share the same highest priority, the router with the highest node number is selected. You can reset the priority to help ensure that it is elected the designated router in its area. The priority is specified on a per-interface basis.
To specify designated routers, use the following command in interface configuration mode:
Router(config-if)# decnet router-priority value
Assigns or changes a priority number to a router on a per-interface basis to receive packets for which no destination is specified.
Configuring Static Routing
Static routing is used when it is not possible or desirable to use dynamic routing. The following are some instances of when you would use static routing:
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To configure static routing, perform any of the tasks in the following sections:
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Configuring a Static Route
You can configure a specific static route and apply it globally even when you use dynamic routing.
To apply a specific static route globally, use the following command in global configuration mode:
Router(config)# decnet route decnet-address next-hop-address [hops [cost]]
Configures a specific static route.
Configuring a Static Route for an Interface
You can select a specific interface for a specific static route when you do not know the address of your neighbor.
To apply a specific static route to a specific interface, use the following command in global configuration mode:
Router(config)# decnet route decnet-address next-hop-type number [snpa-address] [hops [cost]]
Configures a specific static route for a specific interface.
Configuring a Default Static Route
You can configure a default static route and apply it globally, even when you use dynamic routing.
To apply a default static route globally, use the following command in global configuration mode:
Router(config)# decnet route default next-hop-address [hops [cost]]
Configures a default route.
Configuring a Default Static Route for an Interface
You can configure a specific interface for a default static route when you do not know the address of your neighbor.
To apply a default static route to a specific interface, use the following command in global configuration mode:
Router(config)# decnet route default next-hop-type number [snpa-address] [hops [cost]]
Configures a specific default route for a specific interface.
Configuring DECnet Static Route Propagation
When you use static routes or default static routes, you can specify whether the static routes are propagated. By default, DECnet static routes will not be propagated to other routers.
To enable or disable static route propagation, use the following commands in global configuration mode:
Router(config)# decnet propagate static
Enables static route propagation.
Router(config)# no decnet propagate static
Disables static route propagation.
Controlling Access to DECnet Networks
Cisco provides several layers of access control for network security. You can perform any or all of the tasks in the following sections:
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Creating an Access List Based on Source Addresses
You can configure lists globally to control access by source addresses. The standard form of the DECnet access list has a source DECnet address followed by a source-mask address, with bits set wherever the corresponding bits in the address should be ignored. DECnet addresses are written in the form area.node. For example, 50.4 is area 50, node 4. All addresses and masks are in decimal notation.
To create a standard DECnet access list, use the following command in global configuration mode:
Router(config)# access-list access-list-number {permit | deny} source source-mask
Creates an access list to restrict access to a single address.
To disable the list, use the no access-list command.
Creating an Access List Based on Source and Destination Addresses
The extended form of the DECnet access list has a source DECnet address and mask pair, followed by a destination DECnet address and mask pair.
To configure an extended DECnet access list, use the following command in global configuration mode:
Router(config)# access-list access-list-number {permit | deny} source source-mask [destination destination-mask]
Creates an extended access list for several addresses.
To disable the extended access list, use the no access-list command.
Adding Filters to Access Lists
DECnet access lists can be used to filter connect initiate packets. With these packets, you can filter by DECnet object type, such as MAIL.
To add filters to access lists, use the following command in global configuration mode:
Configuring Access Groups
You can restrict access to specific interfaces by applying an access list to them. Interfaces that are associated with the same access list are considered to be an access group.
To configure access groups, use the following command in interface configuration mode:
Router(config-if)# decnet access-group access-list-number
Assigns an access list to a specified interface.
Configuring Routing Filters
You can control access to hello messages or routing information being received or sent on an interface. Addresses that are not in the access list are shown in the update message as unreachable.
To configure routing filters, use either or both of the following commands in interface configuration mode as needed:
Configuring DECnet Accounting
DECnet accounting enables you to collect information about DECnet packets and the number of bytes that are switched through the Cisco IOS software. You collect accounting information based on the source and destination DECnet addresses. DECnet accounting tracks only DECnet traffic that is routed out an interface on which DECnet accounting is configured; it does not track traffic generated by or terminating at the router itself.
DECnet access lists and fast switching support DECnet accounting statistics. Autonomous and silicon switching engine (SSE) switching do not support DECnet accounting statistics.
The Cisco IOS software maintains two accounting databases: an active database and a checkpoint database. The active database contains accounting data tracked until the database is cleared. When the active database is cleared, its contents are copied to the checkpoint database. Using these two databases together enables you to monitor both current traffic and traffic that has previously traversed the router.
To configure DECnet accounting, perform the tasks described in the following sections:
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Enabling DECnet Routing on the Router
To enable DECnet routing, use the following commands in global configuration mode:
Enabling DECnet Accounting
To enable DECnet accounting on a specific interface, use the following commands beginning in global configuration mode:
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For an example of how to enable DEC net accounting on a specific interface, see the "DECnet Accounting Configuration Example" section at the end of this chapter.
Customizing DECnet Accounting
To customize DECnet accounting, use one or more of the following commands in global configuration mode:
Enhancing DECnet Performance
To optimize internetwork performance, perform any or all of the tasks in the following sections:
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Setting Maximum Equal-Cost Paths
You can set the maximum number of equal-cost paths to a destination on a global basis. Limiting the number of equal-cost paths can save memory on routers with limited memory or with very large configurations. Additionally, in networks with a large number of multiple paths and end systems with limited ability to cache out-of-sequence packets, performance might suffer when traffic is split between many paths.
To set maximum equal-cost paths, use the following command in global configuration mode:
Router(config)# decnet [network-number] max-paths value
Sets the maximum number of equal-cost paths to a destination. Paths are set in the routing table.
To display the first hop route to a specified address and to show all equal-cost paths to a single destination, use the show decnet route EXEC command.
Establishing Selection for Paths of Equal Cost
You can establish one of two methods for selecting among paths of equal cost on the router: on a round-robin basis, which is the default, or by configuring Cisco IOS software so that traffic for any higher-layer session is always routed over the same path.
In the round-robin or normal mode, the first packet is sent to the first node, the second packet to the second node, and so on. If the final node is reached before all packets are sent, the next packet in line is sent to the first node, then to the second node, and so forth.
The interim mode supports older implementations of DECnet (VMS versions 4.5 and earlier) that do not support out-of-order packet caching. Other sessions might take another path, thus using equal-cost paths that a router might have for a particular destination.
To select normal or interim mode on the router, use one of the following commands in global configuration mode:
Setting Maximum Visits
You can determine the number of times that a packet can pass through a router. Cisco IOS software ignores packets that have a value greater than the amount of visits you specify. Digital recommends that the value be at least twice the number of maximum hops, to allow packets to reach their destinations when routes are changing.
To set the number of times a packet can pass through a router, use the following command in global configuration mode:
Router(config)# decnet [network-number] max-visits value
Sets the number of times a packet can pass through a router.
Adjusting the Hello Timer
Hosts use the hello messages to identify the hosts with which they can communicate directly. The Cisco IOS software sends hello messages every 15 seconds by default. On extremely slow serial lines, you might want to increase this value on a per-interface basis to reduce overhead.
To adjust the interval for sending hello messages, use the following command in interface configuration mode:
Router(config-if)# decnet hello-timer seconds
Adjusts the interval (in seconds) for sending hello messages on interfaces with DECnet enabled.
Disabling Fast Switching
By default, our DECnet routing software implements fast switching of DECnet packets. You might want to disable fast switching to save memory space on interface cards and to help avoid congestion when high-bandwidth interfaces are writing large amounts of information to low-bandwidth interfaces. Disabling fast switching is especially important when rates slower than T1 are used.
To disable fast switching of DECnet packets, use the following command in interface configuration mode:
Router(config-if)# no decnet route-cache
Disables fast switching of DECnet packets on a per-interface basis.
Setting the Congestion Threshold
If a router configured for DECnet experiences congestion, it sets the congestion-experienced bit. You can define the congestion threshold on a per-interface basis. By setting this threshold, you will cause the system to set the congestion-experienced bit if the output queue has more than the specified number of packets in it.
To set the congestion threshold, use the following command in interface configuration mode:
Router(config-if)# decnet congestion-threshold number
Sets the congestion threshold.
Adjusting the Broadcast Routing Timer
Other routers use broadcast updates to construct local routing tables. Increasing the time between routing updates on a per-interface basis reduces the amount of unnecessary network traffic. Digital calls this parameter the broadcast routing timer because Digital uses a different timer for serial lines. Our DECnet implementation does not make this distinction.
To adjust the broadcast routing timer, use the following command in interface configuration mode:
Router(config-if)# decnet routing-timer seconds
Adjusts how often Cisco IOS software sends routing updates that list all the hosts that the router can reach on a per-interface basis.
Configuring DECnet over DDR
Dial-on-demand routing (DDR) is now supported for DECnet. For more information, refer to the "Dial-on-Demand Routing" section in the Cisco IOS Dial Technologies Configuration Guide.
Configuring DECnet over PPP
DECnet packets can now be fast switched over PPP. For more information, refer to the Cisco IOS Dial Technologies Configuration Guide.
Configuring DECnet over WANs
You can configure DECnet over X.25, SMDS, and Frame Relay networks by configuring the appropriate address mappings as described in the "Configuring X.25 and LAPB," "Configuring SMDS," and "Configuring Frame Relay" chapters in the Cisco IOS Wide-Area Networking Configuration Guide.
Enabling Split Horizon
Split horizon is enabled by default. When split horizon is enabled, routing updates sent out on an interface do not include any information that was originally learned from that interface, and broadcasts are not re-sent on the receiving interface. Disabling split horizon causes Cisco IOS software to include all information in routing updates and to resend broadcast packets on the network from which they were received.
To disable split horizon, use the following command in interface configuration mode:
Router(config-if)# no decnet split-horizon
Disables split horizon when sending routing updates.
Routing DECnet over ISL in Virtual LANs
DECnet can be routed over virtual LAN (VLAN) subinterfaces using the Inter-Switch Link (ISL) encapsulation protocol. Full-feature Cisco IOS software is supported on a per-VLAN basis, allowing standard DECnet capabilities to be configured on VLANs. Refer to the Cisco IOS Switching Services Configuration Guide for information on configuring DECnet routing over ISL in VLANs.
Monitoring and Maintaining the DECnet Network
To clear counters, test network node reachability, and display information about DECnet networks, use the following commands in user EXEC or privileged EXEC mode:
