Indicadores de impacto en la actividad importadora de El Salvador

ƒ ISIS METRIC <metric> <level>

ƒ ISIS PRIORITY <8-bit-number> <level>

ƒ ISIS HELLO-INTERVAL <number-of-seconds>

ƒ ISIS RETRANSMIT-INTERVAL <number-of-seconds>

ƒ ISIS AUTHENTICATION <8-bytes-of-password>

ƒ ISIS CIRCUIT-TYPE <level>

To configure an interface to participate in an IS-IS routing process, use the ip router isis <process id> command in interface configuration mode. To remove an interface, use the no form of this command.

An interface cannot be part of more than one IS-IS process or area, except when an associated routing process performs both Level 1 and Level 2 routing. On media (such as WAN media, for example) where subinterfaces are supported, different subinterfaces can be configured for different IS-IS areas.

Optional IS-IS Interface Configurations

IS-IS metric (cost)—When setting up a new IS-IS process, backbone-wide metrics should be used. The original IS-IS used narrow metrics (six bits), which allows only 63 different values. Wide metrics are 32 bits, obviously providing much more scope and flexibility. Wide metrics should be set as the default in any ISP template for IS-IS. IS-IS has a uniform value of 10 for the link cost. So, to make different links have different costs, configure the IS-IS metric manually. Having only six bits is very restrictive, especially with the larger backbones, so the 32-bit metric makes more sense from the start.

DIS selection— IS-IS priority 100 (the default is 64).

Use this feature in your IS-IS network. Forcibly set your DIS per broadcast segment so that they are known. Choose your most powerful, or most idle routers. Try to keep the DIS limited to one segment per router.

Hello/retransmit timers— isis hello-interval 5 (the default is 10). isis retransmit-interval 3 (the default is five).

This allows for faster network awareness of a failure, and can result in faster reconvergence, but requires more router CPU use and generates more overhead.

isis circuit-type—allows you to control the type of adjacencies formed on an interface (the default is L1/2).

Step 2: Configure IS-IS Process

© 2008 Cisco Systems, Inc. All rights reserved. BCNVC v6.1—2-83

Step 2: Configure IS-IS Process

Enable IS-IS routing, which places the user in router configuration mode

router isis <process-id>

To configure an IS-IS routing process, use the router isis <process id> command in global configuration mode. To remove an IS-IS process, use the no form of this command.

Unlike other routing protocols, enabling IS-IS requires that you create an IS-IS routing process and assign it to a specific interface, rather than to a network. You can specify more than one IS-IS routing process per Cisco device, using multi-area IS-IS configuration.

In general, each routing process corresponds to an area. By default, the first instance of the routing process configured performs both intra-area (Level 1) and interarea (Level 2) routing. You can configure additional router instances, which are automatically treated as Level 1 areas. Routing parameters for each instance of the IS-IS routing process must be configured

individually.

You can configure at most only one IS-IS routing process to perform Level 2 (interarea) routing. A particular Level type can be set per IS-IS routing instance, using the is-type command, which is discussed later in this chapter.

Step 3: Configure NET

© 2008 Cisco Systems, Inc. All rights reserved. BCNVC v6.1—2-84

Step 3: Configure NET

Every router participating in IS-IS requires a unique NET, which is advertised in its PDU

router isis 100

net 49.0002.0101.3103.1252.00

To configure an IS-IS network entity title (NET) for a Connectionless Network Service (CLNS) routing process, use the net command in router configuration mode. To remove a NET, use the no form of this command.

Under most circumstances, only one NET must be configured. A maximum of three NETs per router are allowed. In rare circumstances, it is possible to configure two or three NETs. In such a case, the area that this router is in has three area addresses. There is still only one area, but it has an additional maximum of three area addresses. Configuring multiple NETs can be temporarily useful in the case of network reconfiguration where multiple areas are merged, or where one area is split into additional areas. Multiple area addresses enable you to renumber an area individually as needed. If you are configuring multi area IS-IS, the area ID must be unique, but the system ID portion of the NET must be the same for all IS-IS routing process instances.

Step 4: Set IS-Type (Level)

© 2008 Cisco Systems, Inc. All rights reserved. BCNVC v6.1—2-85

Step 4: Set IS-Type (Level)

is-type level-2-only

Recommended for single-area IP-only networks

To configure the routing level for an instance of the IS-IS routing process, use the is-type command in router configuration mode. To reset the default value, use the no form of this command.

is-type [level-1 | level-1-2 | level-2-only]

In conventional IS-IS configurations, the router acts as both a Level 1 (intra-area) and a Level 2 (interarea) router.

In multi-area IS-IS configurations, the first instance of the IS-IS routing process configured is by default a Level 1-2 (intra-area and interarea) router. The remaining instances of the IS-IS process configured by default are Level 1 routers. You can also use the is-type command to configure Level 2 routing for an area, but it must be the only instance of the IS-IS routing process configured for Level 2 on the Cisco device. A Cisco router can support a maximum of 29 IS-IS processes.