Basic ISIS Net Academy

1NW’2000 Paris © 2000, Cisco Systems, Inc.

The Integrated IS-IS routing protocol

The Integrated IS-IS routing protocol

Gerry [email protected]

Gerry [email protected]


Agenda Agenda

• Link-state protocol fundamentals

• Overview of IS-IS

• Areas and levels

• NSAPs and LSP identifiers

• CLNS routing principles

• LSP Flooding


AgendaAgenda

• IP routing specifics

• Configuration Commands

• Show Commands

• Debug Commands


Link-state protocol fundamentals

Link-state protocol fundamentals

4


About link-state protocolsAbout link-state protocols

• In a link-state protocol, the network can be viewed as a jigsaw puzzle

• Each jigsaw piece holds one router

• Each router creates a packet which represents its own jigsaw piece

This packet is called a Link State PDU (LSP)


About link-state protocolsAbout link-state protocols

• These packets are flooded everywhere

• Therefore each router receives all pieces of the jigsaw puzzle

• Each routers compute SPF algorithm to put the pieces together

Input: all jigsaw puzzle pieces (LSPs)

Output: Area or network topology tree Shortest Path Tree


The jigsaw puzzleThe jigsaw puzzle

LSP for router-A

LSP for router-B

LSP for router-CLSP for router-D

to B

to Eto D

to C

to A

to D to C

to BLSP for routerE

to A to B

to A

to E


All routers have same viewAll routers have same view

• All routers exchange all LSPs

via a reliable flooding mechanism

• All routers store all LSPs in a so-called link-state database (LSPDB)

separate from the routing table (RIB)

all routers should have exactly the same LSPDB, but different RIBs


What to do with LSPs ?What to do with LSPs ?

• Each router ‘composes the jigsaw puzzle’ by executing Dijkstra’s Shortest Path First algorithm (SPF)

the topology is calculated as a Shortest Path Tree (SPT), with itself as root

each router computes a different SPT

• From the SPT the RIBs are calculated


All routers have same LSPDBAll routers have same LSPDB

RouterA’s LSPDB

RouterB’s LSPDB

RouterC’s LSPDB

RouterE’s LSPDB

RouterD’s LSPDB

lspA lspB

lspC lspDlspE

lspA lspB

lspC lspDlspE

lspA lspB

lspC lspDlspE

lspA lspB

lspC lspDlspE

lspA lspB

lspC lspDlspE


Brief Overview of IS-ISBrief Overview of IS-IS

11


What is IS-IS ?What is IS-IS ?

• IS stands for Intermediate System

• IS is “OSI speak” for router

• IS-IS is the Intermediate System to Intermediate System intra-domain routing protocol

• IS-IS was defined in 1992 in the ISO/IEC recommendation 10589


IS-IS for IP routingIS-IS for IP routing

• IS-IS was designed for OSI routing

• IS-IS is easily extendable

• Extensions for IP routing in rfc1195

Also called “Integrated IS-IS”or “Dual IS-IS”

• Easy to extend for other protocols mainly IPv6


Only 4 types of IS-IS packetsOnly 4 types of IS-IS packets

• IS-IS Hello packet (IIH)

• Link State Packet (LSP)

• Partial Sequence Number Packet (PSNP)

• Complete Sequence Number Packet (CSNP)

• Packets are sometimes called Protocol Data Units (PDU in OSI)


IS-IS Hello PDUsIS-IS Hello PDUs

• Also called IIHs

• Used for maintaining adjacencies

• Different on p2p links and LANs

• Different from ISHs and ESHs (ESIS)

• IIHs are padded to full MTU size


Link State PDUsLink State PDUs

• Called LSPs

• Contains all info about one router

adjacencies, connected IP prefixes, OSI endsystems, area addresses, etc.

• One LSP per router (plus fragments)

• One LSP per LAN network


Sequence Number PDUsSequence Number PDUs

• Partial (PSNP) and Complete (CSNP)

• Used when flooding the LSPDB

• PSNPs are like ACKs on p2p links

• CSNPs are used for LSPDB synchronization over LANs

• CSNP are also used to sync LSPDB over new p2p adjacencies


Pseudonodes and network LSAs Pseudonodes and network LSAs

• For SPF, the whole network must look like a collection of nodes and point-to-point links

Multi-access networks are different

• Assume a virtual node for the LAN

this virtual node is called pseudonode. It is not a real router, but just an extra LSP in the LSPDB


A pseudonode on a LAN A pseudonode on a LAN

Logical view

LAN

Physical view

DIS

Pseudonode

DIS


Who creates the pseudonodeWho creates the pseudonode

• Created by Designated Router (DIS)

• No Backup Designated Router in IS-IS

• The DIS reports all LAN neighbors in the pseudonode LSP; with metric 0

• All LAN routers report connectivity to the pseudonode in their LSPs


Identifying nodesIdentifying nodes

• In IS-IS SystemIDs are 6 bytes. Nodes are identified by 7 bytes.

A normal node (non-pseudonode) is identified by 6 bytes systemID plus a zero (e.g. 00c0.0040.1234.00-00 )

A pseudonode is identified by the systemID of the DIS, plus 1 byte from the circuitID of the interface of the DIS

(e.g. 00c0.0040.1234.01-00 )


Areas and levelsAreas and levels

22


Hierarchy Hierarchy

• IS-IS has 2 layers of hierarchy

the backbone is called level-2

areas are called level-1

• Same algorithms apply for L1 and L2

• A router can take part in L1 and L2

inter-area routing (or inter-level routing)


Level-1 RoutersLevel-1 Routers

• Neighbors only in the same area

• L1 has information about own area

• L1-only routers look at the attach-bit (ATT) in L1 LSPs to find the closest L1L2 router

• L1-only routers install a default route to the closest L1L2 router in the area


Level-2 routers Level-2 routers

• May have neighbors in other areas

• L2 has information about L2 topology

• L2 has information what L1 destinations are reachable and how to reach them via the L2 topology

• L2 routers often do also L1 routing

so called L1L2 routers


Adjacency levels

L1-Adjacency L2-Adjacency

L2-AdjacencyL2-Adjacency

L1L2Adjacency

L1L2Adjacency

Router with adjacencies within the same area.

However, needs to have a L2 database as well since it is a transit node

Therefore L1L2 adjacency is required


Level-1, Level-2 & Level-1-2 Routers

• Backbone MUST BE L2 contiguous

L1-only

L1-only

L1-only

L1-only

L1-L2

L1-L2

L2-only

L1-only

L1-L2

L1-L2

L1-only

This router has to behave as level-2 as well in order to guarantee backbone continuity


Level-1, Level-2 & Level-1-2 Routers

• Backbone MUST BE L2 contiguous

L1-only

L1-only

L1-only

L1-L2

L1-L2

L2-only

L1-L2

L1-L2

L1-only

This router has to behave as level-2 as well in order to guarantee backbone continuity

L1-L2


NSAPs and LSPidsNSAPs and LSPids

29


NSAPs and AddressingNSAPs and Addressing

• Network Service Access Point

• The NSAP is the network layer address for CLNS packets

• One NSAP per box, not per interface (similar to DECnet)

• SNPA means SubNetwork Point of Attachment, which is the layer2 or MAC address


How do I read an NSAP ?How do I read an NSAP ?

• An NSAP consists of 3 parts

area-address, systemID and n-selector

• Total length between 8 and 20 bytes

example: 49.0001.0000.0000.0007.00


NETs versus NSAPsNETs versus NSAPs

• A NET is an NSAP with n-selector 0

• A NET implies the routing layer of the IS itself (no transport layer)

• On routers we always deal with NETs

We haven’t implemented TP4 (or another transport layer)


Do I need an NSAP if I want to use IS-IS for IP routing ?

Do I need an NSAP if I want to use IS-IS for IP routing ?

• Yes, still needed for IP routing only

• Area address is like OSPF area nr

• SystemID is like an OSPF routerID

LSP identifier is derived from systemID


Creating unique systemIDsCreating unique systemIDs

• SystemID is 6 bytes

• Start numbering 1, 2, 3, 4 …. etc

• Convert your loopback IP address

192.31.231.16 -> 192.031.231.016 -> systemID 1920.3123.1016


Creating area addressesCreating area addresses

• If you do CLNS routing, request an official NSAP prefix

• If you do just IP routing, use AFI 49

• AFI 49 denotes private address space

like network 10.0.0.0 in IP

• Just number your areas 49.0001… 49.0002…., 49.0003,… etc


LSP IdentifierLSP Identifier

• LSP identifier consists of 3 parts• Source ID

SystemID of router or DIS (if pseudonode)

• Pseudonode IDRouter LSP = zero, Pseudonode LSP = non-zero

• LSP numberFragmentation number

• Example: 00c0.0040.1234.02-00

PN-ID Frag-Nr SystemID


CLNS routing principlesCLNS routing principles

37


OSI protocol familyOSI protocol family

• CLNS is datagram delivery protocol

like bare IP service

actually called CLNP

• ESIS is like ARP, ICMP, HSRP, IRDP

between routers and hosts

• IS-IS and ISO-IGRP are the IGPs


OSI protocol familyOSI protocol family

• IS-IS is not encapsulated in CLNS

and not encapsulated in IP (yet)

• Encapsulated directly in layer2

• Protocol family is OSI

usually values like 0xFE or 0xFEFE

(ppp uses 0x0023 and 0x8023)


Encapsulation of IS-ISEncapsulation of IS-IS

Datalink header (OSI family 0xFEFE)

ISIS fixed header (first byte is 0x82)

ISIS TLVsISIS:


ESIS fixed header (first byte is 0x81)

ESIS TLVsESIS:


CLNS header (with NSAPs) (first byte is 0x80)

User dataCLNS:


Level-1 routingLevel-1 routing

• L1-only routers know only topology of their own area (including all ISs and ESs in the area)

• Traffic to other areas is sent via the closest L2 IS

• L1L2 ISs set the “attached-bit” in their L1 LSP


Area addressesArea addresses

• An area address is like a summary

• All L1 ISs and ESs in an area must have NSAPs that start with the same area-address

• L1L2 routers advertise their area-addresses to L2 routers in other areas

• Multiple area-adresses possible


Level-2 RoutingLevel-2 Routing

• L2 routers know about other areas

L2 area addresses and L2 routers

• When doing OSI routing, the L2 ISs must know their own area. Therefore never use L2-only on OSI routers

L2-only is possible when doing just IP


Level-2 RoutingLevel-2 Routing

• Transit traffic requires routers inside the area to know about other areas

routers in transit paths must be L1L2 routers to have the full L2 LSDB

similar to pervasive BGP requirement

• L2 routers must be contiguous


The BackboneThe Backbone

• A router can’t tell whether it is a transit node

Therefore the cisco default is to be L1L2

This will make the backbone larger then necessary

So always configure L1-only or L2-only when possible

• L1L2 in one area is less scalable

Especially with ISIS for IP


ISIS router cannot determine if they need to be L1 or L1L2Therefore By default all cisco routers will behave as L1L2

Area 4

Can an IS determine its level ? Can an IS determine its level ?

Area 3

Area 2

Area 1“I’m in area 2 and ALL my neighbors are in thesame area. I must be a L1-only router ?”

!! NO !!Rtr C must have a full L2 LSDB to route between areas 1, 3 and 4. Remember, the backbone must be contiguous.


The Attached bit The Attached bit

Area 2 Area 1

rtr A

rtr D

• L1L2 routers set the ATT bit in their L1 LSP

• L1 routers use ATT bit found in L1-LSDB as possible area exit point

ISIS for IP: level-1 router will install a 0.0.0.0/0 route towards the L1L2 with ATT-bit set

• Shortest metric to the L1L2 who sets the ATT bit wins

L2-LSDBrtrA.00-00rtrD.00-00

L1-LSDBrtrA.00-00 ATT-bitrtrB.00-00rtrC.00-00

L1-LSDBrtrD.00-00 ATT-bitrtrE.00-00rtrF.00-00


LSP floodingLSP flooding

48


Why do we need floodingWhy do we need flooding

• All routers generate an LSP

• All LSPs need to be flooded to all routers in the network

if LSPDB is not synchronised, routing loops or blackholes might occur

• IS-IS’ two components are the SPF computation and reliable flooding


What triggers a new LSP ?What triggers a new LSP ?

• When something changes …

Adjacency came up or went down

Interface up/down (connected IP prefix !)

Redistributed IP routes change

Inter-area IP routes change

An interface is assigned a new metric

Most other configuration changes

Periodic refresh


What to do with a new LSP ?What to do with a new LSP ?

• Create new LSP, install in your own LSPDB and mark it for flooding

• Send the new LSP to all neighbors

• Neigbors flood the LSP further


Basic flooding rulesBasic flooding rules

• When receiving an LSP, compare with old version of LSP in LSPDB

• If newer:

install it in the LSPDB

Acknowledge the LSP with a PSNP

Flood to all other neighbors

Check if need to run SPF


Basic flooding rulesBasic flooding rules

• If same age:


• If older:


Send our version of the same LSP

Wait for PSNP


Sequence numberSequence number

• Each LSP (and LSP fragment) has its own sequence number

• When router boots, set seqnr to one

• When there is a change, the seqnr is incremented, a new version of the LSP is generated with the new seqnr

• Higher seqnr means newer LSP


Remaining lifetimeRemaining lifetime

• Used to age out old LSPs

• Periodic refresh needed to keep stable LSPs valid

• IS-IS counts down from 1200 sec to 0

we allow start at 65535 sec (18.7h)

• When lifetime expires, the LSP is purged from the network

Header with lifetime = 0 is flooded


Flooding on a P2P LinkFlooding on a P2P Link

RouterARouterB

Received ackClear SRMbit

Received it. Local copy has seqNr = 21.So the received one is newer. Install it in LSDB. Acknowledge it. Maybe flood further.id=x seqnr=22

PSNP

Now flood it:Set SRM bit.Send over p2p.

id=x seqnr=22LSP

Receives LSPid=x seqNr=22 It’s new. Put it in the LSPDB

id=x seqnr=22LSP


The Designated RouterThe Designated Router

• DIS is like the DR in OSPF

• DIS is only on LANs, not on p2p

• DIS has two tasks

create/update pseudonode LSP

conduct flooding over the LAN

• DIS sends periodic CSNPs

LSPid, SeqNr, Checksum, Lifetime of all LSPs present in the LSPDB


The Designated ISThe Designated IS

• No Backup DIS in ISIS

not necessary, no LSPDB resync

• DIS is elected by priority and MAC

actually is “self-elected”

• LAN circuitID shows who is DIS

use show clns interface


Flooding on a LANFlooding on a LAN

Periodic CSNPevery 10 secs

id=y seqnr=...id=x seqNr=22id=z ...

CSNP

LAN

DISRtr-A

Got it. Install andrun SPF

Local copies of LSP-y and LSP-z are up-to-date but local copy of LSP-x is older.Request latest LSP-x via PSNP

id=x seqNr=21PSNP

!!! Problem !!!Dropped LSP

LSP

Received new LSPid=x seqNr=22Install in LSPDB.Flood the LSP.

id=x seqNr=22LSP

Neighbor has an old LSP, better resend him latest

id=x seqNr=22LSP


IP routing specificsIP routing specifics

60


L1 advertised into L2L1 advertised into L2

• All L1L2 routers advertise all the IP prefixes they learn via L1 into L2

• Only advertise routes you use

(inter-level routing goes via the RIB)

• Summarization possible

- At L1->L2

- when redistributing


L1 advertised into L2L1 advertised into L2

• Level-1 preferred over Level-2

In case of SAME routes (same prefix and same mask)

• Internal equal to external route type

(TLV 128 versus TVL 130)

• Internal over external metric-type


ISIS routing LevelsISIS routing Levels

L1

L1L2

L1

L1L2L12. Level-1 LSP withIP prefix: 10.1.0.0/16

2. Level-1 LSP withIP prefix: 10.10.0.0/16

L1

1. Level-1 LSP withAttached-bit (used as a default route by all level-1routers

3. Level-2 LSP withIP prefix: 10.1.0.0/16IP prefix: 10.10.0.0/16

Routers within an area do not have any routing information about prefixes originated outside the area. Default routing (ATT-bit or explicit 0.0.0.0/0) is used to reach destinations outside the area.


ISIS routing LevelsISIS routing Levels

L1L2

L1

L2L2

L1L2L1

L1L2

L11. Level-1 LSP withIP prefix: 10.1.0.0/16

4. At this point the prefix 10.1.0.0/16 will NOT be inserted in the L1 LSP (no route leaking by default)

2. Level-2 LSP withIP prefix: 10.1.0.0/16 2. Level-2 LSP with

IP prefix: 10.1.0.0/16



2. At this point prefix 10.1.0.0/16 will be inserted in L2 LSP

2. At this point prefix 10.1.0.0/16 is inserted in L2 LSP

0. Level-1 LSP with ATT bit set




Configuration, Show,& Debug CommandsConfiguration, Show,& Debug Commands

65


Command AgendaCommand Agenda

• Basic Configuration Commands

• Important Show Commands

• Useful Debug Commands


Basic ConfigurationCommands


• Router sub-commandsrouter isis <tag name>

net <net>

is-type <L1 L2 L1L2>

default-information originate <route-map> (only for L2)

Hostname-dynamic




• Interface sub-commandsip router isis <tag name>

clns router isis <tag name>

isis metric <value>

isis priority <value>

isis circuit-type <L1 L2 L1L2>

isis hello-interval <seconds>

isis hello-multiplier <value>


Router-B--------------

interface Loopback0

ip address 192.168.1.1 255.255.255.255

!

Interface Serial0

ip address 192.168.120.10 255.255.255.0

ip router isis

!

interface Serial1

ip address 192.168.222.1 255.255.255.0

ip router isis

!

router isis

passive-interface Loopback0

net 49.0001.1921.6800.1001.00

Router-A--------------

interface Loopback0

ip address 192.168.1.5 255.255.255.255

!

interface Serial0

ip address 192.168.120.5 255.255.255.0

ip router isis

!

router isis

is-type level-1


net 49.0001.1921.6800.1005.00

Basic ConfigurationBasic Configuration

Area 49.0001

Rtr-A

Rtr-B

L1L2 routers

L1router

Area 49.0002

Rtr-C

L1router

S0

S1

S0

S1

S0

S1

Rtr-D


Router-C--------------

interface Loopback0

ip address 192.168.2.2 255.255.255.255

!

interface Serial0

ip address 192.168.111.2 255.255.255.0

ip router isis

isis circuit-type level-1

!

interface Serial1

ip address 192.168.222.2 255.255.255.0

ip router isis

isis circuit-type level-2

!

router isis


net 49.0002.1921.6800.2002.00

Router-D--------------

interface Loopback0

ip address 192.168.2.4 255.255.255.255

!

interface Serial1

ip address 192.168.111.4 255.255.255.0

ip router isis

!

router isis

is-type level-1


net 49.0002.1921.6800.2004.00

Basic ConfigurationBasic Configuration

Area 49.0001

Rtr-A

Rtr-B

L1L2 routers

L1router

Area 49.0002

Rtr-C

L1router

S0

S1

S0

S1

S0

S1

Rtr-D


Rtr-B#show clnsGlobal CLNS Information: 2 Interfaces Enabled for CLNS NET: 49.0001.1921.6800.1001.00 Configuration Timer: 60, Default Holding Timer: 300, Packet Lifetime 64 ERPDU's requested on locally generated packets Running IS-IS in IP-only mode (CLNS forwarding not allowed)

Show clnsShow clns

Area 49.0001 Area 49.0002

Rtr-B

Rtr-D

L1L2 routers

L1routers

S0

S1 S0 S0 S1

S1

Rtr-C

Rtr-A


Rtr-B# show clns protocol

IS-IS Router: <Null Tag> System Id: 1921.6800.1001.00 IS-Type: level-1-2 Manual area address(es): 49.0001 Routing for area address(es): 49.0001 Interfaces supported by IS-IS: Serial1 - IP Serial0 - IP Redistribute: static (on by default) Distance for L2 CLNS routes: 110

Show clns protocolShow clns protocol

Area 49.0001

Rtr-A

Rtr-B

L1L2 routers

L1router

Area 49.0002

Rtr-C

L1router

S0

S1

S0

S1

S0

S1

Rtr-D


Rtr-B# show clns neighbors

System Id Interface SNPA State Holdtime Type ProtocolRtr-C Se0 *HDLC* Up 23 L2 IS-IS1921.6800.1005 Se1 *HDLC* Up 21 L1 IS-IS

show clns neighborsshow clns neighbors

Area 49.0001 Area 49.0002

Rtr-B

Rtr-D

L1L2 routers

L1routers

S0

S1 S0 S0 S1

S1

Rtr-C

Rtr-A


Area 49.0001

Rtr-A

Rtr-B

L1L2 routers

L1router

Area 49.0002

Rtr-C

L1router

S0

S1

S0

S1

S0

S1

Rtr-D

Rtr-B# show clns int serial1Serial1 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 47 seconds Routing Protocol: IS-IS Circuit Type: level-1-2 Interface number 0x2, local circuit ID 0x101 Level-1 Metric: 10, Priority: 64, Circuit ID: 1921.6800.1005.00 Number of active level-1 adjacencies: 1 Level-2 Metric: 10, Priority: 64, Circuit ID: Rtr-B.01 Number of active level-2 adjacencies: 0 Next IS-IS Hello in 6 seconds

Show clns interfaceShow clns interface


Rtr-B# show clns int serial0Serial0 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 30 seconds Routing Protocol: IS-IS Circuit Type: level-1-2 Interface number 0x1, local circuit ID 0x100 Level-1 Metric: 10, Priority: 64, Circuit ID: Rtr-C.01 Number of active level-1 adjacencies: 0 Level-2 Metric: 10, Priority: 64, Circuit ID: Rtr-B.00 Number of active level-2 adjacencies: 1 Next IS-IS Hello in 6 seconds

Show clns interfaceShow clns interface

Area 49.0001

Rtr-A

Rtr-B

L1L2 routers

L1router

Area 49.0002

Rtr-C

L1router

S0

S1

S0

S1

S0

S1

Rtr-D


Rtr-B# show isis database

IS-IS Level-1 Link State Database:LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OLRtr-B.00-00 * 0x00000020 0x0C24 674 1/0/01921.6800.1005.00-00 0x00000023 0x909E 830 0/0/01921.6800.1005.01-00 0x00000017 0xC896 841 0/0/0

IS-IS Level-2 Link State Database:LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OLRtr-B.00-00 * 0x00000024 0x7D98 748 0/0/0Rtr-C.00-00 0x00000028 0x1E01 1128 0/0/0

Show isis databaseShow isis database

Area 49.0001 Area 49.0002

Rtr-B

Rtr-D

L1L2 routers

L1routers

S0

S1 S0 S0 S1

S1

Rtr-C

Rtr-A


Rtr-B# show isis database 1921.6800.1001.00-00 detailIS-IS Level-1 LSP Rtr-B.00-00LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OLRtr-B.00-00 * 0x00000020 0x0C24 424 1/0/0 Area Address: 49.0001 NLPID: 0xCC Hostname: Rtr-B IP Address: 192.168.1.1 Metric: 0 IP 192.168.1.1 255.255.255.255 Metric: 10 IP 192.168.222.0 255.255.255.0 Metric: 10 IP 192.168.120.0 255.255.255.0 Metric: 10 IS 1921.6800.1005.00

IS-IS Level-2 LSP Rtr-B.00-00LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OLRtr-B.00-00 * 0x00000025 0x7B99 1186 0/0/0 Area Address: 49.0001 NLPID: 0xCC Hostname: Rtr-B IP Address: 192.168.1.1 Metric: 10 IS Rtr-C.00 Metric: 10 IP 192.168.120.0 255.255.255.0 Metric: 0 IP 192.168.1.1 255.255.255.255 Metric: 20 IP 192.168.1.5 255.255.255.255 Metric: 10 IP 192.168.222.0 255.255.255.0

Show isis database detailShow isis database detail


Rtr-B# show isis lsp-log

Level 1 LSP log When Count Interface Triggers01:50:44 1 CONFIG01:50:35 1 Loopback0 IPUP01:50:28 1 Serial0 IPUP01:50:20 1 Serial1 IPUP01:50:20 1 Serial1 NEWADJ01:50:18 1 ATTACHFLAG01:36:49 1 Loopback0 CONFIG

Level 2 LSP log When Count Interface Triggers01:50:46 1 CONFIG01:50:36 1 Loopback0 IPUP01:50:30 2 Serial0 NEWADJ IPUP01:50:22 1 Serial1 IPUP01:50:10 1 IPIA01:48:21 1 Serial0 DELADJ01:48:16 1 Serial0 NEWADJ01:36:51 1 Loopback0 CONFIG

Show isis lsp-logShow isis lsp-log

Area 49.0001

Rtr-A

Rtr-B

L1L2 routers

L1router

Area 49.0002

Rtr-C

L1router

S0

S1

S0

S1

S0

S1

Rtr-D


Rtr-B# show isis spf-log

Level 1 SPF log When Duration Nodes Count First trigger LSP Triggers02:16:52 0 1 1 Rtr-B.00-00 NEWLSP02:16:42 0 1 1 Rtr-B.00-00 TLVCODE02:16:32 0 1 2 Rtr-B.00-00 NEWADJ TLVCONTENT02:16:22 8 3 4 Rtr-B.00-00 ATTACHFLAG LSPHEADER

TLVCON TENT02:02:57 4 3 1 Rtr-B.00-00 TLVCONTENT02:01:52 8 3 1 PERIODIC01:46:52 8 3 1 PERIODIC01:31:53 8 3 1 PERIODIC01:16:52 8 3 1 PERIODIC01:01:52 8 3 1 PERIODIC00:46:52 8 3 1 PERIODIC00:31:51 8 3 1 PERIODIC00:16:51 8 3 1 PERIODIC00:01:50 64 3 1 PERIODIC

Show isis spf-logShow isis spf-log

Area 49.0001

Rtr-A

Rtr-B

L1L2 routers

L1router

Area 49.0002

Rtr-C

L1router

S0

S1

S0

S1

S0

S1

Rtr-D


Level 2 SPF log When Duration Nodes Count First trigger LSP Triggers02:16:54 0 1 1 Rtr-B.00-00 NEWLSP02:16:44 0 1 1 Rtr-B.00-00 TLVCODE02:16:34 8 2 3 Rtr-B.00-00 NEWADJ NEWLSP TLVCONTENT02:14:29 8 2 3 Rtr-B.00-00 NEWADJ TLVCONTENT02:14:23 4 2 1 Rtr-C.00-00 TLVCODE02:13:56 8 2 1 Rtr-C.00-00 TLVCONTENT02:02:59 4 2 1 Rtr-B.00-00 TLVCONTENT02:01:54 4 2 1 PERIODIC01:46:54 4 2 1 PERIODIC01:31:54 4 2 1 PERIODIC01:16:54 4 2 1 PERIODIC01:01:54 4 2 1 PERIODIC00:46:53 4 2 1 PERIODIC00:31:53 4 2 1 PERIODIC00:16:53 4 2 1 PERIODIC00:01:53 60 2 1 PERIODIC

Show isis spf-logShow isis spf-log

L1L2 routers

Area 49.0001

Rtr-A

Rtr-B

L1router

Area 49.0002

Rtr-C

L1router

S0

S1

S0

S1

S0

S1

Rtr-D


Show clns trafficShow clns traffic

• LSPs sourced indicates stability of IS

• LSP retransmissions should stay low

• PRCs can not be checked elsewhere

• LSP checksum errors are a bad sign

• Update queue should not stay full

• Update queue should not drop much



Rtr-B# show clns trafficCLNS: Time since last clear: neverCLNS & ESIS Output: 669, Input: 4773CLNS Local: 0, Forward: 0CLNS Discards: Hdr Syntax: 0, Checksum: 0, Lifetime: 0, Output cngstn: 0 No Route: 0, Discard Route: 0, Dst Unreachable 0, Encaps. Failed: 0 NLP Unknown: 0, Not an IS: 0CLNS Options: Packets 0, total 0 , bad 0, GQOS 0, cngstn exprncd 0CLNS Segments: Segmented: 0, Failed: 0CLNS Broadcasts: sent: 0, rcvd: 0Echos: Rcvd 0 requests, 0 replies Sent 0 requests, 0 repliesESIS(sent/rcvd): ESHs: 0/0, ISHs: 669/660, RDs: 0/0, QCF: 0/0ISO-IGRP: Querys (sent/rcvd): 0/0 Updates (sent/rcvd): 0/0ISO-IGRP: Router Hellos: (sent/rcvd): 0/0ISO-IGRP Syntax Errors: 0

IS-IS: Time since last clear: neverIS-IS: Level-1 Hellos (sent/rcvd): 282/0

L1L2 routers

Area 49.0001

Rtr-A

Rtr-B

L1router

Area 49.0002

Rtr-C

L1router

S0

S1

S0

S1

S0

S1

Rtr-D



IS-IS: Level-2 Hellos (sent/rcvd): 285/0IS-IS: PTP Hellos (sent/rcvd): 420/415IS-IS: Level-1 LSPs sourced (new/refresh): 8/2IS-IS: Level-2 LSPs sourced (new/refresh): 9/1IS-IS: Level-1 LSPs flooded (sent/rcvd): 5/8IS-IS: Level-2 LSPs flooded (sent/rcvd): 7/8IS-IS: LSP Retransmissions: 0IS-IS: Level-1 CSNPs (sent/rcvd): 1/1IS-IS: Level-2 CSNPs (sent/rcvd): 2/2IS-IS: Level-1 PSNPs (sent/rcvd): 7/4IS-IS: Level-2 PSNPs (sent/rcvd): 7/5IS-IS: Level-1 DR Elections: 1IS-IS: Level-2 DR Elections: 1IS-IS: Level-1 SPF Calculations: 7IS-IS: Level-2 SPF Calculations: 9IS-IS: Level-1 Partial Route Calculations: 1IS-IS: Level-2 Partial Route Calculations: 5IS-IS: LSP checksum errors received: 0IS-IS: Update process queue depth: 0/200IS-IS: Update process packets dropped: 0

L1L2 routers

Area 49.0001

Rtr-A

Rtr-B

L1router

Area 49.0002

Rtr-C

L1router

S0

S1

S0

S1

S0

S1

Rtr-D


Rtr-B# debug isis adj-packetsIS-IS Adjacency related packets debugging is onRtr-B#05:45:21: ISIS-Adj: rcvd state UP, old state UP, new state UP05:45:21: ISIS-Adj: Action = ACCEPT05:45:24: ISIS-Adj: Sending serial IIH on Serial0, length 149905:45:26: ISIS-Adj: Rec serial IIH from *HDLC* (Serial1), cir type L1, cir id 00, length 149905:45:26: ISIS-Adj: rcvd state UP, old state UP, new state UP05:45:26: ISIS-Adj: Action = ACCEPT05:45:26: ISIS-Adj: Sending serial IIH on Serial1, length 149905:45:31: ISIS-Adj: Rec serial IIH from *HDLC* (Serial0), cir type L1L2, cir id01, length 1499

Debug isis adj-packetsDebug isis adj-packets

Area 49.0001 Area 49.0002

Rtr-B

Rtr-D

L1L2 routers

L1routers

S0

S1 S0 S0 S1

S1

Rtr-C

Rtr-A


Debug isis snp-packetsDebug isis snp-packets

Rtr-B# debug isis snp-packetsIS-IS CSNP/PSNP packets debugging is on

07:51:59: ISIS-Snp: Build L2 PSNP entry for 1921.6800.2002.00-00, seq 3507:51:59: ISIS-Snp: Sending L2 PSNP on Serial007:53:50: ISIS-Snp: Rec L1 PSNP from 1921.6800.1005 (Serial1)07:53:50: ISIS-Snp: PSNP entry 1921.6800.1001.00-00, seq 31, ht 119707:53:50: ISIS-Snp: Same entry 1921.6800.1001.00-00, seq 3107:54:26: ISIS-Snp: Build L1 PSNP entry for 1921.6800.1005.00-00, seq 2F07:54:26: ISIS-Snp: Sending L1 PSNP on Serial107:55:18: ISIS-Snp: Rec L2 PSNP from 1921.6800.2002 (Serial0)07:55:18: ISIS-Snp: PSNP entry 1921.6800.1001.00-00, seq 32, ht 119707:55:18: ISIS-Snp: Same entry 1921.6800.1001.00-00, seq 32

Area 49.0001 Area 49.0002

Rtr-B

Rtr-D

L1L2 routers

L1routers

S0

S1 S0 S0 S1

S1

Rtr-C

Rtr-A


Debug isis spf-triggersDebug isis spf-triggers

Rtr-B# debug isis spf-triggersIS-IS SPF triggering events debugging is onRtr-B#07:32:10: ISIS-Spf: L1 SPF needed, periodic SPF, from 0x356C8DC07:32:10: ISIS-Spf: L2 SPF needed, periodic SPF, from 0x356C8DCRtr-B#conf tRtr-B(config)#int serial0Rtr-B(config-if)#isis metric 15Rtr-B(config-if)# ^Z07:38:27: ISIS-Spf: L1 SPF needed, new metric, from 0x3560762Rtr-B(config)#int serial0Rtr-B(config-if)#shutRtr-B(config-if)# ^Z07:39:23: ISIS-Spf: L2, 1921.6800.1001.00-00 TLV contents changed, code 0x207:39:28: ISIS-Spf: L1 SPF needed, L2 attach changed, from 0x357CF3607:39:28: ISIS-Spf: L1, LSP fields changed 1921.6800.1001.00-00

L1L2 routers

Area 49.0001

Rtr-A

Rtr-B

L1router

Area 49.0002

Rtr-C

L1router

S0

S1

S0

S1

S0

S1

Rtr-D


Lab TopologyLab Topology

R1

R2

R4 R5

R3

49.0

001

49.0002

L1L2

L1L1

L1

L1L2


Lab InstructionsLab Instructions

1. Configure R1 and R2 to belong to the same area. Configure each to route CLNS and IP data. Configure the serial link to only form L1 adjacencies.

2. Configure R2 and R3 to form an L2 adjacency; IP only.

3. Configure R3, R4 and R5 to belong to the same area; IP only.

4. Configure R5 so its systemID will be used to build the Psuedonode for the ethernet segment.


Lab ExerciseLab Exercise

1. What command can be used to confirm the R1 and R2 are enabled to route IP and CLNS packets?

2. What command did you issue to verify that only an L2 adjacency was formed between R2 and R3?

3. Is the ATT bit set in area 49.0002? If so, what command should you use to confirm it has been set?

4. What command do you use to display the Pseudonode LSP of the ethernet segment? What is the metric to each of the nodes listed?

5. Determine if R1 displays the IP subnet of the ethernet segment in area 49.0002. If it does not display the route, why not?

90© 2000, Cisco Systems, Inc.

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