The IS-IS routing protocol is a link-state protocol, as opposed to distance-vector protocols such as Interior Gateway Routing Protocol (IGRP) and Routing Information Protocol (RIP). Link-state offers several advantages over distance-vector protocols. It is faster converging, supports much larger internetworks, and is less susceptible to routing loops. Features of IS-IS includes:
> Hierarchical routing
> Classless behavior
> Fast Convergence
> Very scalable
> Rapid flooding of new information
> Flexible timer tuning
Integrated IS-IS supports three types of networks:
1) OSI only (CLNS)
2) IP only
3) Dual (that is, both OSI and IP simultaneously)
A two-level hierarchy is used to support large routing domains. A large domain may be administratively divided into areas. Each system resides in exactly one area.1 Routing within an area is referred to as Level 1 routing. Routing between areas is referred to as Level 2 routing. A Level 2 Intermediate System (IS) keeps track of the paths to destination areas. A Level 1 IS keeps track of the routing within its own area. For a packet destined for another area, a Level 1 IS sends the packet to the nearest Level 2 IS in its own area, regardless of what the destination area is. Then the packet travels via Level 2 routing to the destination area, where it may travel via Level 1 routing to the destination. It should be noted that selecting an exit from an area based on Level 1 routing to the closest Level 2 IS might result in suboptimal routing.2
Basic IS-IS Configuration Steps:
The following steps should be taken when configuring IS-IS on router:
Step 1: Define areas. Prepare an addressing plan for the routers and determine interfaces that will run Integrated IS-IS.
Step 2: Enable IS-IS as an IP routing protocol on the routers.
The "router is-is [tag] global" configuration command enables Integrated IS-IS on the router.
Step 3: Configure the NETs on the routers. This identifies the routers for IS-IS.
After the Integrated IS-IS process is enabled, the router must be identified for IS-IS by assigning a NET to the router with the "net network-entity-title" configuration command. In this command, network-entity-title is the NET that specifies the area address and the system ID for the IS-IS routing process.
Step 4: Enable Integrated IS-IS on the proper interfaces on the routers.
Then finally interfaces that are to use IS-IS to distribute their IP information must be configured using the "ip router isis [tag]" interface configuration command
When routing of CLNS packets is also required, use the "clns router isis [tag]" interface configuration command.
The beauty of ISIS is ,you can configure IPv4 and IPv6,VRF within same process and enable ISIS under interface,protocol automatically understand.
Configuration example of ISIS for IPv6:
Enter configuration commands, one per line. End with CNTL/Z.
Router(config-if)#ipv6 router isis
“Use Serviceability Features to Troubleshoot your Cat9K as a Cisco TAC Engineer”
This special event is open only to Cisco Customers and Partners.
Many pages in the Cisco Community are accessible only to Cisco customers, partners, or logged in ...
i am new to this and learning by doing on the waywhat i try to achieve in the moment is to reroute the port 80 on pc 0to 100 on pc 0 this is how i forward external internet trafic to itip nat inside source static tcp 10.1.1.1 100 interface Cellular0/...
hi everyone this topic is been posted few time and there were some solutions but its not working. Below are the logs from a access layer switch(c3650) which blocks the trunk port. this switch is connected to a layer 3 switch(c3850) in that switch its...