Table of contents
1. The basic ip address configuration of the whole network
3. (Optional) Adjust the priority of the interface to change the DIS role
1. Check whether an ISIS neighbor status is established between adjacent routers
Features
IS-IS, the intra-domain routing information exchange protocol from Intermediate System to Intermediate System, is a dynamic routing protocol originally designed by the International Organization for Standardization ISO for its connectionless network protocol. In order to provide routing support for IP, IETF has expanded and modified IS-IS so that it can be applied in both TCP/IP and OSI environments, which is called integrated IS-IS. IS-IS belongs to the interior gateway protocol (IGP), which is a link state protocol and uses the shortest path first algorithm for route calculation.
IS-IS router role
1) The Level-1 router is responsible for the routing in the area. It only maintains a Level-1 LSDB, which contains the routing information of the area, and forwards the packets outside the area to the nearest Level-1-2 router;
2) Level-2 routers are responsible for inter-area routing. It maintains a Level-2 LSDB that contains inter-area routing information. All Level-2 routers and Level-1-2 routers form the backbone network of the routing domain and are responsible for Communication between different regions;
3) The Level-1-2 router belongs to both Level-1 and Level-2 routes. The Level-1-2 router maintains two LSDBs. The Level-1 LSDB is used for intra-area routing, and the Level-2 LSDB is used for Inter-area routing.
NET address in S-IS
In the IS-IS protocol, protocol packets such as Hello and LSP used to establish neighbors and exchange routing information between ISs are directly carried in OSI data link frames, unlike other IGPs carried by IP. The format of these protocol messages is the OSI message format, and the messages contain OSI addresses. In the OSI architecture, OSI addresses are used to identify network devices and establish topology information. OSI addresses use the NSAP address format.
The IDP part is specified by ISO, 1byte, composed of AFI, IDI, usually 49, 47 or 86. In the integration with ISIS, the NSAP address is divided into three parts: area address, System ID, and NSEL.
Area address: The HO-DSP in the DSP of the IDP is used together to identify the area in the routing domain, so (IDP, HO-DSP) are called the area address together. Generally, a router only needs to be configured with one area address, and all nodes in the same area have the same area address.
System id: System ID is used to uniquely identify the terminal system or router in the area, and its length is fixed at 6 bytes. System ID can be specified in different ways, but it must be able to uniquely identify the terminal system or router. Generally, System ID is converted from Router ID or MAC address.
NESL: The role is similar to the protocol identifier in IP, and different transmissions correspond to different NSELs. In IP, NSEL is 00.
NET (Network Entity Title, network entity name) refers to the network layer information of the IS itself, excluding the transport layer information, and can be regarded as a special type of NSAP, that is, the NSAP address whose NSEL is 0. NET has the same length as NSAP, with a maximum of 20 bytes and a minimum of 8 bytes.
For example: net 49.0836.0110.6315.2013.00 address, the network number is 49.0836 System ID=0110.6315.2013 NSEL=00
How to change IP address to SYSTEM ID:
Application Scenario
It is usually used in carrier networks, or in some large-scale private networks, involving a large number of routers.
1. Networking requirements
The routers in the whole network run the IS-IS protocol, so that the routes in the whole network are reachable.
2. Network topology
3. Configuration points
1. The basic ip address configuration of the whole network
2. Enable the ISIS routing protocol for the entire network routing, and advertise the corresponding interface to the designated area
3. (Optional) Adjust the priority of the interface to change the DIS role
4. Configuration steps
1. The basic ip address configuration of the whole network
R1(config)#inter lo0
R1(config-if-Loopback 0)#ip add 192.168.1.1 255.255.255.0
R1(config)#inter gi0/0
R1(config-if-GigabitEthernet 0/0)#ip add 9.9.12.1 255.255.255.0
R2(config)#inter lo0
R2(config-if-Loopback 0)#ip add 192.168.2.2 255.255.255.0
R2(config)#inter gigabitEthernet 3/0/0
R2(config-if-GigabitEthernet 3/0/0)#ip add 9.9.12.2 255.255.255.0
R2(config-if-GigabitEthernet 3/0/0)#exit
R2(config)#inter gigabitEthernet 3/0/1
R2(config-if-GigabitEthernet 3/0/1)#ip add 9.9.23.2 255.255.255.0
R3(config)#inter lo0
R3(config-if-Loopback 0)#ip add 192.168.3.3 255.255.255.0
R3(config)#inter gigabitEthernet 0/1
R3(config-if-GigabitEthernet 0/1)#ip add 9.9.23.3 255.255.255.0
2. Enable ISIS for the entire network routing, and notify the corresponding interface to the IS-IS protocol
R1(config)#router isis 100
R1(config-router)#net 49.0591.1921.6800.1001.00
R1(config-router)#is-type level-1 //Configure the role of the router as Level-1
R1(config-router)#exit
R1(config)#inter lo0
R1(config-if-Loopback 0)#ip router isis 100 //j The corresponding interface is declared to ISIS
R1(config-if-Loopback 0)#exit
R1(config)#inter gigabitEthernet 0/0
R1(config-if-GigabitEthernet 0/0)#ip router isis 100
R2(config)#router isis 100
R2(config-router)#net 49.0591.1921.6800.2002.00
R2(config-router)#exit
R2(config)#inter lo0
R2(config-if-Loopback 0)#ip router isis 100
R2(config-if-Loopback 0)#exit
R2(config)#inter gigabitEthernet 3/0/0
R2(config-if-GigabitEthernet 3/0/0)#ip router isis 100
R2(config-if-GigabitEthernet 3/0/0)#inter gi3/0/1
R2(config-if-GigabitEthernet 3/0/1)#ip router isis 100
R2(config-if-GigabitEthernet 3/0/1)#exi
R3(config)#router isis 100
R3(config-router)#net 49.0592.1921.6800.3003.00
R3(config-router)#exit
R3(config)#inter gigabitEthernet 0/1
R3(config-if-GigabitEthernet 0/1)#ip router isis 100
R3(config-if-GigabitEthernet 0/1)#exit
R3(config)#inter lo0
R3(config-if-Loopback 0)#ip router isis 100
3. (Optional) Adjust the priority of the interface to change the DIS role
illustrate:
There are two comparison parameters for the DIS election: interface priority and MAC address. Here, adjust the priority of the interconnection interface between R2 and R1, so that the interface of R2 takes the DIS role.
R2(config)#inter gigabitEthernet 3/0/0
R2(config-if-GigabitEthernet 3/0/0)#isis priority 127 level-1
R1# sh isis neighbors detail
Area 100:
System Id Type IP Address State Holdtime Circuit Interface
R2 L1 9.9.12.2 Up 7 R2.02 GigabitEthernet 0/0
Adjacency ID: 1
Uptime: 00:08:47
Area Address(es): 49.0591
SNPA: 001a.a93c.12fd
Level-1 Protocols Supported: IPv4
5. Configuration Verification
1. Check whether an ISIS neighbor status is established between adjacent routers
R1#show clns is-neighbors detailArea 100:System Id Type IP Address State Holdtime Circuit InterfaceR2 L1 9.9.12.2 Up 26 R1.02 GigabitEthernet 0/0Adjacency ID: 1Uptime: 00:03:52Area Address(es): 49.0591SNPA: 001a.a93c.12fdLevel-1 Protocols Supported: IPv4R2#sh clns is-neighborsArea 100:System Id Type IP Address State Holdtime Circuit InterfaceR1 L1 9.9.12.1 Up 8 R1.02 GigabitEthernet 3/0/0R3 L2 9.9.23.3 Up 9 R3.01 GigabitEthernet 3/0/1R3#sh clns is-neighborsArea 100:System Id Type IP Address State Holdtime Circuit InterfaceR2 L2 9.9.23.2 Up 24 R3.01 GigabitEthernet 0/1
2. Check the routes of the routers in the entire network. If each router can learn the routes of the entire network, the ISIS configuration is correct.
R1#sh ip route
Codes: C - connected, S - static, R - RIP, B - BGP
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
Gateway of last resort is 9.9.12.2 to network 0.0.0.0
i*L1 0.0.0.0/0 [115/10] via 9.9.12.2, 00:00:58, GigabitEthernet 0/0 //The default L1 role router cannot learn the L2 route, it will learn the default route
C 9.9.12.0/24 is directly connected, GigabitEthernet 0/0
C 9.9.12.1/32 is local host.
i L1 9.9.23.0/24 [115/20] via 9.9.12.2, 00:02:45, GigabitEthernet 0/0
C 192.168.1.0/24 is directly connected, Loopback 0
C 192.168.1.1/32 is local host.
i L1 192.168.2.0/24 [115/20] via 9.9.12.2, 00:02:55, GigabitEthernet 0/0
R3#ping 192.168.1.1Sending 5, 100-byte ICMP Echoes to 192.168.1.1, timeout is 2 seconds:< press Ctrl+C to break >!!!!!