The Complete IS-IS Routing Protocol- P13:IS-IS has always been my favourite Interior Gateway Protocol. Its elegant simplicity, its well-structured data formats, its flexibility and easy extensibility are all appealing – IS-IS epitomizes link-state routing. Whether for this reason or others, IS-IS is the IGP of choice in some of the world’s largest networks. Thus, if one is at all interested in routing, it is well worth the time and effort to learn IS-IS. | 350 13. IS-IS Extensions hannes@Frankfurt show isis database extensive . TLVs Area address 3 Speaks IP IPv6 IP router id IP address Hostname Stockholm IS neighbor Metric 1 IP address . IOS command output London show isis database verbose IS-IS Level-2 Link State Database LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT P OL . 0x00000040 0xD323 491 0 0 0 Area Address NLPID 0x81 IS neighbor Metric 63 . The LSP shown in the IOS command output does not contain the Hostname TLV. As it does not list any IP-related TLVs it may be that this is a CLNS-only router that is probably running older software that does not support the Hostname TLV. If the hostnames made their way into the hostname cache then all IS-IS occurrences of the System-ID are replaced using their respective name. See Table for how Pennsauken s System Node and LSP-IDs are represented using the new name resolution service. Today IS-IS is one of the most convenient routing protocols. It aids the network engineer and troubleshooter by offering a kind of distributed name service. All of the IS-IS-related display functions like displaying adjacencies examining the link-state database or logging functions make use of a System-ID to hostname translation cache and display System-IDs Node-IDs and LSP-IDs with their name rather than their hexadecimal representation. The next extension to IS-IS will cover the authentication scheme of LSPs and their implementation. Authenticating Routing Information 351 Authenticating Routing Information Authenticating routing protocol messages is a basic building block for every network security strategy. Some people argue that authentication is pushing the envelope for IS-IS since all the messages run natively on Layer 2 which means that the protocol cannot be exposed to a remote attack from the Internet because there is simply no possibility for .
