© 2006 Cisco Systems, Inc. All rights reserved. BSCI v The IS-IS Protocol Configuring Basic Integrated IS-IS

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Integrated IS-IS: Requires NET Addresses Common CLNS parameters (NET) and area planning are still required even in an IP environment. Even when Integrated IS-IS is used for IP routing only, routers still establish CLNS adjacencies and use CLNS packets.

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v OSI Area Routing: Building an OSI Forwarding Database (Routing Table) When databases are synchronized, Dijkstras algorithm (SPF) is run on the LSDB to calculate the SPF tree. The shortest path to the destination is the lowest total sum of metrics. Separate route calculations are made for Level 1 and Level 2 routes in Level 1-2 routers. Best paths are placed in the OSI forwarding database (CLNS routing table).

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Building an IP Routing Table Partial route calculation (PRC) is run to calculate IP reachability. Because IP and ES are represented as leaf objects, they do not participate in SPF. Best paths are placed in the IP routing table following IP preferential rules. They appear as Level 1 or Level 2 IP routes.

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Integrated IS-IS Configuration Steps 1. Define areas, prepare addressing plan (NETs) for routers, and determine interfaces. 2. Enable IS-IS on the router. 3. Configure the NET. 4. Enable Integrated IS-IS on the appropriate interfaces. Do not forget interfaces to stub IP networks, such as loopback interfaces (although there are no CLNS neighbors there).

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Step 1: Define Area and Addressing Area determined by NET prefix –Assign to support two-level hierarchy. Addressing –IP: Plan to support summarization. –CLNS: Prefix denotes area. System ID must be unique.

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Step 2: Enable IS-IS on the Router router isis [area-tag] router(config)# Enables the IS-IS routing protocol –area-tagname for a process When routing of CLNS packets is also needed, use the clns routing command.

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Step 3: Configure the NET net network-entity-title Router(config-router)# Configures an IS-IS NET address for the routing process

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Step 4: Enable Integrated IS-IS ip router isis [area-tag] router(config-if)# Includes an interface in an IS-IS routing process

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Simple Integrated IS-IS Example interface FastEthernet0/0 ip address ip router isis ! interface Serial 0/0/1 ip address ip router isis ! router isis net The configured router acts as an IP-only Level 1-2 router.

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Change IS-IS Router Level is-type {level-1 | level-1-2 | level-2-only} Router(config-router)# Configures the IS-IS level globally on a router; the default is Level 1-2.

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Change IS-IS Interface Level isis circuit-type {level-1 | level-1-2 | level-2-only} Router(config-if)# Configures the type of adjacency on an interface; the default is Level 1-2.

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Change IS-IS Metric isis metric metric [delay-metric [expense-metric [error- metric]]] {level-1 | level-2} Router(config-if)# Configures the metric for an interface; the default is 10. Metric value is from 1 to 63. Router(config-router)# metric default-value {level-1 | level-2} Alternately, configures the metric globally for all interfaces

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Example: Tuning IS-IS Configuration Change router type on R1 and R3. Change interface levels on R2. Change metric on S0/0/1.

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v IP Summarization summary-address address mask [level-1 | level-2 | level-1-2] [tag tag-number] [metric metric-value] Router(config-router)# P3R1(config-router)# summary-address level-1-2 Creates summary Default is Level 2 Example Summarizes /23 into Level 1-2

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Example: Is Integrated IS-IS Running? R2#show ip protocols Routing Protocol is "isis" Invalid after 0 seconds, hold down 0, flushed after 0 Outgoing update filter list for all interfaces is not set Incoming update filter list for all interfaces is not set Redistributing: isis Address Summarization: None Maximum path: 4 Routing for Networks: FastEthernet0/0 Loopback0 Serial0/0/1 Routing Information Sources: Gateway Distance Last Update :00: :00:03 Distance: (default is 115) R2# Displays the parameters and current state of the active routing protocol processes Router# show ip protocols

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Example: Are There Any IP Routes? R2#show ip route isis /24 is subnetted, 5 subnets i L [115/45] via , Serial0/0/1 i L [115/20] via , FastEthernet0/0 R2# Displays the current state of the routing table show ip route [address [mask]] | [protocol [process-id]] router#

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v show clns Router# Displays information about the CLNS network Troubleshooting Commands: CLNS show clns [area-tag] protocol Router# Lists the protocol-specific information show clns interface [type number] Router# Lists the CLNS-specific information about each interface show clns [area-tag] neighbors [type number] [detail] Router# Displays both ES and IS neighbors

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v show isis [area-tag] route Router# Displays IS-IS Level 1 routing table (system IDs) (requires that CLNS routing be enabled) Troubleshooting Commands: CLNS and IS-IS show clns route [nsap] Router# Displays IS-IS routing table (areas) show isis [area-tag] database Router# Displays the IS-IS LSDB show isis [area-tag] topology Displays IS-IS least-cost paths to destinations Router#

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Routing in a Two-Level Area Structure Example: OSI Intra-Area and Interarea Routing

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Level 1 and Level 2 Topology Table R1#show isis topology IS-IS paths to level-1 routers System Id Metric Next-Hop Interface SNPA R1 -- R2 10 R2 Fa0/ c470 R2#show isis topology IS-IS paths to level-1 routers System Id Metric Next-Hop Interface SNPA R1 10 R1 Fa0/ fdb0 R2 -- IS-IS paths to level-2 routers System Id Metric Next-Hop Interface SNPA R1 ** R2 -- R3 35 R3 Se0/0/1 *HDLC*

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Simple Troubleshooting: What About CLNS Protocol? R2# show clns protocol IS-IS Router: System Id: IS-Type: level-1-2 Manual area address(es): Routing for area address(es): Interfaces supported by IS-IS: Loopback0 - IP Serial0/0/1 - IP FastEthernet0/0 - IP Redistribute: static (on by default) Distance for L2 CLNS routes: 110 RRR level: none Generate narrow metrics: level-1-2 Accept narrow metrics: level-1-2 Generate wide metrics: none Accept wide metrics: none

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Are Adjacencies Established? R2# show clns neighbors System Id Interface SNPA State Holdtime Type Protocol R3 Se0/0/1 *HDLC* Up 28 L2 IS-IS R1 Fa0/ fdb0 Up 23 L1 IS-IS R2#show clns interface s0/0/1 Serial0/0/1 is up, line protocol is up Checksums enabled, MTU 1500, Encapsulation HDLC ERPDUs enabled, min. interval 10 msec. CLNS fast switching enabled CLNS SSE switching disabled DEC compatibility mode OFF for this interface Next ESH/ISH in 45 seconds Routing Protocol: IS-IS Circuit Type: level-2 Interface number 0x1, local circuit ID 0x100 Neighbor System-ID: R3 Level-2 Metric: 35, Priority: 64, Circuit ID: R2.00 Level-2 IPv6 Metric: 10 Number of active level-2 adjacencies: 1 Next IS-IS Hello in 5 seconds if state UP

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Summary Integrated IS-IS routing for IP uses CLNS and therefore requires CLNS addresses, that is, NET addresses. Integrated IS-IS requires planning the addresses, enabling the router, defining the router NET, and enabling the appropriate interfaces. IS-IS can be optimized by adjusting adjacency levels and changing the default metric cost. IS-IS summarization can be configured with the summary-address command. The show ip protocols and show ip route commands verify the IS-IS configuration and IP functionality. Various show commands are used to troubleshoot CLNS IS- IS structures and Integrated IS-IS networks

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v