DECnet Configuration Guide, Cisco IOS Release 15SY

Configuring DECnet

The Configuring DECnet module describes how to configure the Cisco implementation of the DECnet routing protocol.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the "Feature Information for Configuring DECnet" section.

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Contents

•How to Configure Cisco Implementation of the DECnet Routing Protocol

•Configuration Examples for Cisco Implementation of the DECnet Routing Protocol

•Additional References

•Feature Information for Configuring DECnet

How to Configure Cisco Implementation of the DECnet Routing Protocol

•Enabling DECnet Routing (required)

•Enabling Concurrent Routing and Bridging (optional)

•Configuring DECnet on Token Rings (optional)

•Configuring Address Translation (optional)

•Specifying Name-to-DECnet Address Mapping (optional)

•Enabling Phase IV-to-Phase V Conversion (optional)

•Propagating Phase IV VAX Clusters to Phase V Areas (optional)

•Propagating Phase IV Areas Through an OSI Backbone (optional)

•Establishing the Routing Table Size (optional)

•Configuring Level 1 Routers (optional)

•Configuring Level 2 Routers (optional)

•Specifying Designated Routers (optional)

•Configuring Static Routing (optional)

•Controlling Access to DECnet Networks (optional)

•Configuring DECnet Accounting (optional)

•Enhancing DECnet Performance (optional)

•Configuring DECnet over DDR (optional)

•Configuring DECnet over PPP (optional)

•Configuring DECnet over WANs (optional)

•Routing DECnet over ISL in Virtual LANs (optional)

•Monitoring and Maintaining the DECnet Network (optional)

Enabling DECnet Routing

•Enabling DECnet Phase IV Routing or Enabling DECnet Phase IV Prime Routing (required)

•Assigning a DECnet Cost to Each Interface (required)

•Specifying the DECnet Node Type (required)

Enabling DECnet Phase IV Routing

To enable DECnet Phase IV routing, use the following command in global configuration mode:

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 1 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 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, ensure that you 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.

Note To use DECnet and Internet Packet Exchange (IPX) routing concurrently on the same interface, you must enable DECnet routing first, then enable IPX routing without specifying the optional MAC address. If you enable IPX first and then DECnet, IPX routing is disrupted.

After you enable DECnet routing, use the show interfaces EXEC command to obtain the MAC addresses. To disable DECnet routing, use the no decnet routing command.

Figure 1 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 where 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 apart from 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 "Examples: DECnet Phase IV Prime" 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 2 shows four routers (three Ethernet interfaces) 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 2 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 "Example: DECnet" 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 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 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 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 an example of how to configure address translation, see the "Example: Address Translation" 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 3 in the "Example: Address Translation" 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.

Note Cisco does not support Poor Man's Routing directly; the intermediate nodes must be VMS systems with Poor Man's Routing enabled in the file-access language.

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:

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 Connectionless Network Service (CLNS) configured on your router; then use the following command in global configuration mode:

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 "Example: Phase IV-to-Phase V Conversion" 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 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.

Note For the conversion between Phase IV and Phase V to function, the Phase V area must be numbered so that it matches the converted Phase IV area.

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 hold time 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:

To propagate Phase IV VAX clusters to Phase V areas, perform the tasks in these sections:

•Enabling Phase IV-to-Phase V Conversion

•Configuring CLNS IS-IS

•Configuring DECnet Cluster Alias Updates and Setting the DECnet Cluster Hold Time

Enabling Phase IV-to-Phase V Conversion

To enable Phase IV-to-Phase V conversion, use the following commands beginning in global configuration mode:

Configuring CLNS IS-IS

To enable Connectionless Network Service (CLNS) Intermediate System-to-Intermediate System (IS-IS), use the following commands in global configuration mode:

Configuring DECnet Cluster Alias Updates and Setting the DECnet Cluster Hold Time

To configure DECnet cluster alias updates and set the DECnet cluster hold time, 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 "Example: Phase IV VAX Cluster Alias to Phase V Areas" 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:

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:

For an example of how to enable a Phase IV area through an OSI backbone, see the "Example: Phase IV Areas Through an OSI Backbone" 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 other interarea routers.

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:

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:

•The routers do not support the same dynamic routing protocol.

•Your network includes WAN links that involve paying for connect time or for per-packet charges.

•You want routers to advertise connectivity to external networks, but you are not running an interdomain routing protocol.

•You must interoperate with equipment from another vendor that does not support any of the dynamic routing protocols that we support.

•The router operates over X.25, Frame Relay, or Switched Multimegabit Data Service (SMDS) networks.

Note An interface that is configured for static routing cannot reroute around failed links.

To configure static routing, perform any of the tasks in the following sections:

•Configuring a Static Route (Optional)

•Configuring a Static Route for an Interface (Optional)

•Configuring a Default Static Route (Optional)

•Configuring a Default Static Route for an Interface (Optional)

•Configuring DECnet Static Route Propagation (Optional)

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:

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:

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:

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:

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:

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:

•Creating an Access List Based on Source Addresses (Optional)

•Creating an Access List Based on Source and Destination Addresses (Optional)

•Adding Filters to Access Lists (Optional)

•Configuring Access Groups (Optional)

•Configuring Routing Filters (Optional)

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:

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:

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:

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 of 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:

•Enabling DECnet Routing on the Router

•Enabling DECnet Accounting

•Customizing DECnet Accounting

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:

Note If DECnet accounting is enabled on an interface but no accounting list is specified, DECnet accounting will track all traffic through the interface, up to the accounting threshold limit.

For an example of how to enable DEC net accounting on a specific interface, see the "Example: DECnet Accounting Configuration" 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:

•Setting Maximum Equal-Cost Paths (Optional)

•Establishing Selection for Paths of Equal Cost (Optional)

•Setting Maximum Visits (Optional)

•Adjusting the Hello Timer (Optional)

•Disabling Fast Switching (Optional)

•Setting the Congestion Threshold (Optional)

•Adjusting the Broadcast Routing Timer (Optional)

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:

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:

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:

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:

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:

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:

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:

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:

Configuring MOP

To enable Maintenance Operation Protocol (MOP) on an interface, use the following command in interface configuration mode:

Note To disable MOP packets on member links, disable MOP on the port-channel interface by using the no mop enabled command.

To enable an interface to send out periodic MOP system identification messages on an interface, use the following command in interface configuration mode:

Note There is no emission of MOP frames on an interface that is configured with xconnect. MOP remains enabled on the xconnect interface.

Configuration Examples for Cisco Implementation of the DECnet Routing Protocol

•Examples: DECnet Phase IV Prime

•Example: DECnet

•Example: Address Translation

•Example: 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

Examples: DECnet Phase IV Prime

This section includes examples of configuring DECnet Phase IV Prime support for inherent MAC addresses. The comments in these examples point out some possible configuration errors, in addition to explaining correct command lines.

The following example shows how to configure an Ethernet interface 0 for DECnet Phase IV Prime:

decnet routing iv-prime 1.1

interface ethernet 0

 decnet cost 10

! Router is bilingual on Ethernet interface 0.

The following example shows how to configure a Token Ring interface 1 with a MAC address that is not supported by DECnet Phase IV:

decnet routing 2.1	

interface tokenring 1

 decnet cost 5

 mac-address 0000.0c00.62e6 

! Interface Token Ring 1 has MAC address as set.

! This is an error because the Token Ring interface has a MAC address that is 

! not Phase IV-compatible, and the router is not running Phase IV Prime.

The following example shows how to configure the router to support DECnet Phase IV Prime later in the configuration:

interface tokenring 1

 decnet cost 5

 mac-address 0000.0c00.62e6 

! Invalid configuration, because router is only Phase IV.

 decnet routing iv-prime 5.5

! Become a Phase IV Prime router.

interface tokenring 1

 mac-address 0000.0c00.62e6 

! Valid configuration because the router is now running Phase IV Prime.

The following example shows valid and invalid ways of using the decnet multicast-map command:

decnet routing iv-prime 3.4

interface tokenring 1

 decnet multicast-map phiv-prime-all-bridges c000.2000.0000 

! Invalid value (phiv-prime-all-bridges) for multicast ID string.

interface tokenring 1

 decnet multicast-map iv-prime-all-routers d000.2000.0000 

! Invalid value (d000.2000.0000) for functional address.

interface tokenring 1

 decnet multicast-map iv-prime-all-routers c000.2000.0000 

! This will work. The command redefines the multicast to functional address

! mapping for the "all Phase IV Prime routers" multicast.

Example: DECnet

The following example shows the commands required for enabling DECnet. DECnet routing is established on a router at address 4.27. The node is configured as a Level 2, or interarea router. A cost of four is set for the Ethernet interface 0. A cost of ten is set for the serial 1 interface.

decnet routing 4.27

decnet node area

interface ethernet 0

 decnet cost 4

interface serial 1

 decnet cost 10

Example: Address Translation

In Figure 3, the router is connected to two DECnet networks using Ethernet. The following example shows how to configure an ATG between Network 0 and Network 1.

Figure 3 ATG Configuration Example

In Network 0, the router is configured at address 19.4 and is a Level 1 router. In Network 1, the router is configured at address 50.5 and is an area router. At this point, no routing information is exchanged between the two networks. Each network in the router has a separate routing table.

decnet 0 routing 19.4

decnet 0 node routing-iv

interface ethernet 0

 decnet 0 cost 1

!

decnet 1 routing 50.5

decnet 1 node area

interface ethernet 1

 decnet 1 cost 1

The following example shows how to establish a translation map:

decnet 0 map 19.5 1 50.1

decnet 1 map 47.1 0 19.1

Packets in Network 0 sent to virtual address 19.5 will be routed to Network 1, and the destination address will be translated to 50.1. Packets sent to virtual address 47.1 in Network 1 will be routed to Network 0 as 19.1.

Table 1 defines the parameters for the translation map.

Network 0 uses a block of addresses from its area to map the remote nodes. In Network 0, the router will advertise nodes 19.5 and 19.6. These nodes must not already exist in Network 0.

Network 1 uses another area for the address translation. Because Cisco IOS software will be advertising the availability of area 47, that area should not already exist in Network 1 because DECnet area fragmentation could occur.

Only nodes that exist in the maps on both networks will be able to communicate directly. Network 0 node 19.1 will be able to communicate with Network 1 node 50.1 (as 19.5), but will not be able to communicate directly with Network 1 node 60.1.

When naming nodes, use the appropriate address in each network. See the configurations that follow for examples.

Network 0 VMS NCP Command File Sample

$MCR NCP

define node 19.1 name A

define node 19.2 name B

define node 19.3 name C

define node 19.4 name GS

define node 19.5 name D

define node 19.6 name F

Network 1 VMS NCP Command File Sample

$MCR NCP

define node 50.1 name D

define node 50.5 name GS

define node 60.1 name E

define node 19.1 name F

define node 47.1 name A

define node 47.2 name C

Example: Phase IV-to-Phase V Conversion

Figure 4 shows that for the DECnet Phase IV-to-Phase V conversion to work properly, Connectionless Network Service (CLNS) Intermediate System-to-Intermediate System (IS-IS) must be configured on certain interfaces.

Note that although Router A has only Phase IV hosts connected by its Ethernet 0 interface, the interface must be configured for CLNS IS-IS for Router A to convert the Phase IV adjacency information into Phase V. If the Ethernet interface 0 on Router A is not configured for CLNS IS-IS, Router B will never receive information about Router D and end node 1.

Figure 4 Sample Phase IV-to-Phase V Network Conversion

Configuration for Router A

decnet routing 1.1

decnet conversion 49

clns routing

router isis

 net 49.0001.aa00.0400.0104.00

interface ethernet 0

 clns router isis

 decnet cost 4

interface serial 0

 clns router isis

Sample Configuration for Router D

decnet routing 1.10

interface ethernet 0

 decnet cost 4

Example: Phase IV VAX Cluster Alias to Phase V Areas

The following example shows the commands required for allowing Phase IV VAX cluster alias to be reachable by Phase V areas. Note that cluster alias updates will only be propagated when Phase IV-to-Phase V conversion has been enabled, the router has been configured for CLNS IS-IS, and the decnet cluster-alias update command has been entered in order to allow updates. For the Ethernet interface 1/0 interface, a DECnet cost of four and a DECnet cluster holdtime of 200 seconds has been entered:

decnet routing 1.1

decnet conversion 49

clns routing

router isis

 net 49.0001.aa00.0400.0104.00

interface ethernet 1/0

 clns router isis

 decnet cost 4

 decnet cluster 200

 decnet cluster-alias update

Example: Phase IV Areas Through an OSI Backbone

The following example shows how to configure border routers to propagate Phase IV areas through an OSI backbone using the advertise feature. In this example, Router X in area 8 wants to communicate with Router Y in area 9.

Figure 5 illustrates the network, and the configurations that follow illustrate the commands required for enabling the advertise feature.

Figure 5 Sample Phase IV/Phase V Backbone Network

Configuration for Router B

decnet conversion 49

! Propagate Area 9 reachability information

decnet advertise 9 4 2

! Create dummy OSI route to force conversion to Phase IV

clns route 49.0008 discard

Configuration for Router C

decnet conversion 49

! Propagate Area 8 reachability information

decnet advertise 8 6 3

! Create dummy OSI route to force conversion to Phase IV

clns route 49.0009 discard

The routing table for Router A will then contain the following, as displayed with the show decnet route EXEC command:

  Area       Cost  Hops   Next Hop to Node       Expires  Prio

*1             0     0     (Local) -> 1.1

*8             4     1   Ethernet1 -> 8.1           35     64    A

*9             5     2   Ethernet0 -> 1.2

  Node       Cost  Hops   Next Hop to Node       Expires  Prio

*(Area)        0     0     (Local) -> 1.1

*1.1           0     0     (Local) -> 1.1

*1.2           4     1   Ethernet4 -> 1.2           38     64    VA

The routing table for Router B will then contain the following:

  Area       Cost  Hops   Next Hop to Node       Expires  Prio

*1             0     0     (Local) -> 1.2

*8             8     2   Ethernet0 -> 1.1

*9             4     2       (OSI) -> 1.2

  Node       Cost  Hops   Next Hop to Node       Expires  Prio

*(Area)        0     0     (Local) -> 1.2

*1.1           4     1   Ethernet0 -> 1.1           37     64    VA

*1.2           0     0     (Local) -> 1.2

The routing table for Router C will then contain the following:

  Area       Cost  Hops   Next Hop to Node       Expires  Prio

*2             0     0     (Local) -> 2.1

*8             6     3       (OSI) -> 2.1

*9             8     2   Ethernet0 -> 2.2

  Node       Cost  Hops   Next Hop to Node       Expires  Prio

*(Area)        0     0     (Local) -> 2.1

*2.1           0     0     (Local) -> 2.1

*2.2           4     1   Ethernet0 -> 2.2           33     64    VA

Example: DECnet Accounting Configuration

Figure 6 illustrates DECnet accounting configured on the outbound serial interfaces for Router A and Router C. Note that because Router A and Router C exist in two different DECnet areas, they must be configured as interarea, or Level 2, routers.

Figure 6 DECnet Accounting Configuration

On Router A, DECnet accounting is enabled on an interface that is routing DECnet traffic. With no other commands used for the interface configuration, DECnet accounting on Router A tracks all DECnet traffic outbound on that interface up to the default accounting threshold of 512 source and destination pair addresses.

Configuration for Router A

decnet routing 3.2

decnet node-type area

interface serial 0

 decnet cost 20

 decnet accounting

interface ethernet 0

 decnet cost 4

Router B is configured to track traffic between all pairs specified in the decnet accounting list command. Router B also tracks traffic for pairs not specified in the decnet accounting list command up to the value specified for the decnet accounting transit command. If traffic between a source and destination endpoint pair not listed traverses the router, that traffic is added to the aggregate value, which appears in the display for the show decnet accounting command.

Configuration for Router B

decnet routing 12.7

interface serial 0

 decnet cost 20

 decnet accounting

interface serial 1

 decnet cost 20

 decnet accounting

decnet node type area

decnet accounting list 3.4 10.5

decnet accounting list 3.7 10.5

decnet accounting list 3.4 10.3

decnet accounting transits 2

Router C is configured to track DECnet traffic according to the values specified with the DECnet commands. The accounting threshold is set to 1000, which means that DECnet accounting will track all traffic passing through the router for up to 1000 source and destination address pairs.

Configuration for Router C

decnet routing 10.4

decnet node-type area

interface serial 0

 decnet cost 20

 decnet accounting

 decnet accounting threshold 1000

interface ethernet 0

 decnet cost 4

Additional References

Related Documents

Standards and RFCs

MIBs

Technical Assistance

Feature Information for Configuring DECnet

Table 2 lists the features in this module and provides links to specific configuration information.

Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Note Table 2 lists only the Cisco IOS software release that introduced support for a given feature in a given Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS software release train also support that feature.

Cisco and the Cisco logo are trademarks or registered trademarks of Cisco and/or its affiliates in the U.S. and other countries. To view a list of Cisco trademarks, go to this URL: www.cisco.com/go/trademarks. Third-party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1110R)

Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

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