IS-IS: Basic Configuration

IS-IS: Basic Configuration

               

IS-IS:

·         IS-IS is an Interior Gateway Protocol (IGP) developed in the 1980s as the Routing Protocol for Open System Interconnection; RFC 1142.

·         When IS-IS is used to support IP, it is called Integrated IS-IS (RFC 1195)

·         IS-IS is also a link-state protocol like OSPF and runs SPF Algorithm to find the best routes.

·         There is no Area-0 in IS-IS, But Backbone area (level-2) is a set of L1/L2 and L2 routers and has to be contiguous

·         In OSPF, each link belongs to an Area, but in IS-IS each Router belongs to an Area.

·         Integrated IS-IS still requires OSI address, called a “Connection-Less Network Services”, CLNS address.

·         NSAP Address:

o    NSAP Address varies from 8 to 20 octets and it has three parts.

·         Area Address: Area is like an IP Subnet, describing a group or location

·         System ID: ID identifies a particular member in that location, like the host portion of IP address

·         NSEL: Similar to a TCP port, identifies the process on the host.

o    Ex: 49.0001.1111.1111.1111.00

·         All Cisco routers have NSEL 00

·         System-ID is always 6 bytes length

·         In the OSI, 49 represent Private address.

·         The NET address is a NSAP address of the Host, with the NSEL set to 00

·         In IS-IS terminology, a router is called Intermediate System (IS)

·         Intermediate Systems can be in 3 Levels of Routing Hierarchy.

o    L1, Level1: Which is responsible for intra-area routing

o    L1/L2, Level-1-2: Responsible for intra-area and inter-area routing

o    L2, Level-2: Inter-area only

Let me take a small topology to configure IS-IS:

·         R1 & R2: Area1

·         R3 & R4: Area2

·         R5: Area3

Net Address:

·         R1: 49.0001.1111.1111.1111.00

·         R2: 49.0001.2222.2222.2222.00

·         R3: 49.0002.3333.3333.3333.00

·         R4: 49.0002.4444.4444.4444.00

·         R5: 49.0003.5555.5555.5555.00

Configuration:

R1(config-if)#router isis

R1(config-router)#net 49.0001.1111.1111.1111.00

R1(config-router)#is-type level-1

R1(config-router)#int ser1/0

R1(config-if)#ip router isis

R1#

R1#show clns neighbors

System Id      Interface   SNPA                State  Holdtime  Type Protocol

R2             Se1/0       *HDLC*              Up     27        L1   IS-IS

R1#

R2(config-if)#router isis

R2(config-router)#net 49.0001.2222.2222.2222.00

R2(config-router)#is-type level-1-2

R2(config-router)#int ser1/0

R2(config-if)#ip router isis

R2(config-if)#isis circuit-type level-1

R2(config-if)#int ser1/1

R2(config-if)#ip router isis

R2(config-if)#isis circuit-type level-2-only

R2(config-if)#

R2#show clns neighbors

System Id      Interface   SNPA                State  Holdtime  Type Protocol

R1             Se1/0       *HDLC*              Up     26        L1   IS-IS

R3             Se1/1       *HDLC*              Up     26        L2   IS-IS

R2#

R3(config-if)#router isis

R3(config-router)#net 49.0002.3333.3333.3333.00

R3(config-router)#is-type level-2-only

R3(config-router)#int ser1/1

R3(config-if)#ip router isis

R3(config-if)#int ser1/0

R3(config-if)#ip router isis

R3(config-if)#end

R3#

R3#show clns neighbors

System Id      Interface   SNPA                State  Holdtime  Type Protocol

R2             Se1/1       *HDLC*              Up     25        L2   IS-IS

R4             Se1/0       *HDLC*              Up     27        L2   IS-IS

R3#

R4(config-if)#router isis

R4(config-router)#net 49.0002.4444.4444.4444.00

R4(config-router)#is-type level-2-only

R4(config-router)#int ser1/0

R4(config-if)#ip router isis

R4(config-if)#int ser1/1

R4(config-if)#ip router isis

R4(config-if)#end

R4#show clns neighbors

System Id      Interface   SNPA                State  Holdtime  Type Protocol

R3             Se1/0       *HDLC*              Up     27        L2   IS-IS

R5             Se1/1       *HDLC*              Up     23        L2   IS-IS

R4#

R5(config-if)#router isis

R5(config-router)#net 49.0003.5555.5555.5555.00

R5(config-router)#is-type level-2-only

R5(config-router)#int ser1/1

R5(config-if)#ip router isis

R5(config-if)#end

R5#show clns neighbors

System Id      Interface   SNPA                State  Holdtime  Type Protocol

R4             Se1/1       *HDLC*              Up     20        L2   IS-IS

R5#

R1#show clns

Global CLNS Information:

  1 Interfaces Enabled for CLNS

  NET: 49.0001.1111.1111.1111.00

  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)

R1#

R2#show clns

Global CLNS Information:

  2 Interfaces Enabled for CLNS

  NET: 49.0001.2222.2222.2222.00

  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)

R2#

R3#show clns

Global CLNS Information:

  2 Interfaces Enabled for CLNS

  NET: 49.0002.3333.3333.3333.00

  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)

R3#

R4#show clns

Global CLNS Information:

  2 Interfaces Enabled for CLNS

  NET: 49.0002.4444.4444.4444.00

  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)

R4#

R5#show clns

Global CLNS Information:

  1 Interfaces Enabled for CLNS

  NET: 49.0003.5555.5555.5555.00

  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)

R5#

R1#show clns interface ser1/0

Serial1/0 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 28 seconds

  Routing Protocol: IS-IS

    Circuit Type: level-1-2

    Interface number 0x0, local circuit ID 0x100

    Neighbor System-ID: R2

    Level-1 Metric: 10, Priority: 64, Circuit ID: R2.00

    Level-1 IPv6 Metric: 10

    Number of active level-1 adjacencies: 1

    Next IS-IS Hello in 4 seconds

    if state UP

R1#

R2#show clns interface ser1/0

Serial1/0 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 12 seconds

  Routing Protocol: IS-IS

    Circuit Type: level-1

    Interface number 0x0, local circuit ID 0x100

    Neighbor System-ID: R1

    Level-1 Metric: 10, Priority: 64, Circuit ID: R2.00

    Level-1 IPv6 Metric: 10

    Number of active level-1 adjacencies: 1

    Next IS-IS Hello in 6 seconds

    if state UP

R2#

R2#show clns interface ser1/1

Serial1/1 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 3 seconds

  Routing Protocol: IS-IS

    Circuit Type: level-2

    Interface number 0x1, local circuit ID 0x101

    Neighbor System-ID: R3

    Level-2 Metric: 10, Priority: 64, Circuit ID: R2.01

    Level-2 IPv6 Metric: 10

    Number of active level-2 adjacencies: 1

    Next IS-IS Hello in 2 seconds

    if state UP

R2#

R3#show clns interface ser1/1

Serial1/1 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 32 seconds

  Routing Protocol: IS-IS

    Circuit Type: level-1-2

    Interface number 0x0, local circuit ID 0x100

    Neighbor System-ID: R2

    Level-2 Metric: 10, Priority: 64, Circuit ID: R3.00

    Level-2 IPv6 Metric: 10

    Number of active level-2 adjacencies: 1

    Next IS-IS Hello in 8 seconds

    if state UP

R3#

R3#show clns interface ser1/0

Serial1/0 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 18 seconds

  Routing Protocol: IS-IS

    Circuit Type: level-1-2

    Interface number 0x1, local circuit ID 0x101

    Neighbor System-ID: R4

    Level-2 Metric: 10, Priority: 64, Circuit ID: R3.01

    Level-2 IPv6 Metric: 10

    Number of active level-2 adjacencies: 1

    Next IS-IS Hello in 428 milliseconds

    if state UP

R3#

R4#show clns interface ser1/1

Serial1/1 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 37 seconds

  Routing Protocol: IS-IS

    Circuit Type: level-1-2

    Interface number 0x1, local circuit ID 0x101

    Neighbor System-ID: R5

    Level-2 Metric: 10, Priority: 64, Circuit ID: R4.01

    Level-2 IPv6 Metric: 10

    Number of active level-2 adjacencies: 1

    Next IS-IS Hello in 5 seconds

    if state UP

R4#

R4#show clns interface ser1/0

Serial1/0 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 22 seconds

  Routing Protocol: IS-IS

    Circuit Type: level-1-2

    Interface number 0x0, local circuit ID 0x100

    Neighbor System-ID: R3

    Level-2 Metric: 10, Priority: 64, Circuit ID: R4.00

    Level-2 IPv6 Metric: 10

    Number of active level-2 adjacencies: 1

    Next IS-IS Hello in 3 seconds

    if state UP

R4#

R5#show clns interface ser1/1

Serial1/1 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 33 seconds

  Routing Protocol: IS-IS

    Circuit Type: level-1-2

    Interface number 0x0, local circuit ID 0x100

    Neighbor System-ID: R4

    Level-2 Metric: 10, Priority: 64, Circuit ID: R5.00

    Level-2 IPv6 Metric: 10

    Number of active level-2 adjacencies: 1

    Next IS-IS Hello in 5 seconds

    if state UP

R5#

R1#show ip route

Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP

       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

       E1 - OSPF external type 1, E2 - OSPF external type 2

       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

       ia - IS-IS inter area, * - candidate default, U - per-user static route

       o - ODR, P - periodic downloaded static route

Gateway of last resort is 100.1.12.2 to network 0.0.0.0

     1.0.0.0/32 is subnetted, 1 subnets

C       1.1.1.1 is directly connected, Loopback0

     100.0.0.0/24 is subnetted, 1 subnets

C       100.1.12.0 is directly connected, Serial1/0

i*L1 0.0.0.0/0 [115/10] via 100.1.12.2, Serial1/0

R1#ping 100.1.45.5

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 100.1.45.5, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 124/138/156 ms

R1#

R2#show ip route

Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP

       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

       E1 - OSPF external type 1, E2 - OSPF external type 2

       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

       ia - IS-IS inter area, * - candidate default, U - per-user static route

       o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

     2.0.0.0/32 is subnetted, 1 subnets

C       2.2.2.2 is directly connected, Loopback0

     100.0.0.0/24 is subnetted, 4 subnets

i L2    100.1.34.0 [115/20] via 100.1.23.3, Serial1/1

i L2    100.1.45.0 [115/30] via 100.1.23.3, Serial1/1

C       100.1.12.0 is directly connected, Serial1/0

C       100.1.23.0 is directly connected, Serial1/1

R2#

R3#show ip route

Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP

       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

       E1 - OSPF external type 1, E2 - OSPF external type 2

       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

       ia - IS-IS inter area, * - candidate default, U - per-user static route

       o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

     100.0.0.0/24 is subnetted, 4 subnets

C       100.1.34.0 is directly connected, Serial1/0

i L2    100.1.45.0 [115/20] via 100.1.34.4, Serial1/0

i L2    100.1.12.0 [115/20] via 100.1.23.2, Serial1/1

C       100.1.23.0 is directly connected, Serial1/1

     3.0.0.0/32 is subnetted, 1 subnets

C       3.3.3.3 is directly connected, Loopback0

R3#

R4#show ip route

Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP

       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

       E1 - OSPF external type 1, E2 - OSPF external type 2

       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

       ia - IS-IS inter area, * - candidate default, U - per-user static route

       o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

     100.0.0.0/24 is subnetted, 4 subnets

C       100.1.34.0 is directly connected, Serial1/0

C       100.1.45.0 is directly connected, Serial1/1

i L2    100.1.12.0 [115/30] via 100.1.34.3, Serial1/0

i L2    100.1.23.0 [115/20] via 100.1.34.3, Serial1/0

     4.0.0.0/32 is subnetted, 1 subnets

C       4.4.4.4 is directly connected, Loopback0

R4#

R5#show ip route

Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP

       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

       E1 - OSPF external type 1, E2 - OSPF external type 2

       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

       ia - IS-IS inter area, * - candidate default, U - per-user static route

       o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

     100.0.0.0/24 is subnetted, 4 subnets

i L2    100.1.34.0 [115/20] via 100.1.45.4, Serial1/1

C       100.1.45.0 is directly connected, Serial1/1

i L2    100.1.12.0 [115/40] via 100.1.45.4, Serial1/1

i L2    100.1.23.0 [115/30] via 100.1.45.4, Serial1/1

     5.0.0.0/32 is subnetted, 1 subnets

C       5.5.5.5 is directly connected, Loopback0

R5#ping 100.1.12.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 100.1.12.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 88/120/152 ms

R5#