Later adapted to carry IP prefixes in addition to CLNP. (known as Integrated or Dual IS-IS) as described in. RFC ▫ Predominantly used in ISP environment . Unused Features Some features defined in RFC are not in current use. Parker Informational [Page 2] RFC Interoperable IP Networks using IS-IS May. Intermediate System to Intermediate System is a routing protocol designed to move information (IP), the Network Layer protocol of the global Internet. This version of the IS-IS routing protocol was then called Integrated IS-IS (RFC ) .

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Supported Standards for IS-IS

IS-IS is neutral regarding the type of network addresses for which it can route. Views Read Edit View history.

From Wikipedia, the free encyclopedia. This article is about a computer network protocol. OSPF has a larger set of extensions and optional features specified in the protocol standards. The result is that an IS-IS router is only ever a part of a single area. Routing information is exchanged between Level 1 routers and other Level 1 routers of the same area, and Level 2 routers can only form relationships and exchange information with other Level 2 routers.


SPB allows for shortest-path forwarding in an Ethernet mesh network context utilizing multiple equal cost paths. IS-IS routers are designated as being: However IS-IS is easier to expand: The logical view is that OSPF creates something of a spider web or star topology of many areas all attached directly to Area Zero and IS-IS by contrast creates a logical topology of a backbone of Level 2 routers with branches of Level 1—2 and Level 1 routers forming the individual areas.

RFC – Use of OSI IS-IS for routing in TCP/IP and dual environments

IS-IS has been called “the de facto standard for large service provider network backbones. IS-IS is a link-state routing protocoloperating by reliably flooding link state information throughout a network of routers. All articles with unsourced statements Articles with unsourced statements from February Pages 195 RFC magic links. The complete IS-IS routing protocol. This page was last edited on 28 Issiat ISO standards by standard number.

In addition to that, IS-IS is less “chatty” and can scale to support larger networks.

By using this site, you agree to the Terms of Use and Privacy Policy. Level 1—2 routers exchange information with both levels and are used to connect the inter area routers with the intra area routers.

Level 1 intra-area ; Level 2 inter area ; isi Level 1—2 both. Each IS-IS router independently builds a database of the network’s topology, aggregating the flooded network information. Packets datagrams are then forwarded, based on the computed ideal path, through the network to the destination.


For topics with similar names, see Isis disambiguation. International Organization for Standardization. As a result, they are conceptually similar. Both support variable length subnet maskscan use multicast to discover neighboring routers using hello packetsand can support authentication of routing updates. However, the basic concepts are similar.

IS-IS – Wikipedia

Retrieved May 24, Intermediate System to Intermediate System IS-ISalso written ISIS is a routing protocol designed to move information efficiently within a computer networka group of physically connected computers or similar devices. It accomplishes this by determining the best route for data through a packet-switched network. IS-IS is an interior gateway protocoldesigned for use within an administrative domain or network.

This permits SPB to support large Layer 2 topologies, with fast convergence, and improved use of the mesh topology.

Retrieved from ” https: This map indicates the subnets which each IS-IS router can reach, and the lowest-cost shortest path to a subnet is used to forward traffic.