The Complete IS-IS Routing Protocol- P16: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. | 442 15. Troubleshooting Show Commands Following our troubleshooting plan illustrated in Figure we need show commands to supply the current state of the network. The five main commands that we will use shortly to examine JUNOS and IOS are in the areas of Displaying the IS-IS related interface properties Displaying the adjacency table Displaying the link-state database Displaying the results of the SPF calculation Displaying the routing table First the show commands for IOS will be discussed. In IOS all five commands are not in the same command hierarchy. Some commands are tucked beneath the show clns some in the show isis and others in the show ip command keyword hierarchy. IOS Show Commands In the IOS command line hierarchy all commands that deal with adjacency management and interface-related configuration are under the show clns branch. The two main commands to display IS-IS interface properties and adjacency tables are the show clns interface and show clns neighbor command. IOS command output The output of the show clns command contains many OSI-related fields which reveals that the initial purpose for IS-IS was to route OSI traffic. Below the routing protocol stanza the output shows level metric and number of active adjacencies information. London show clns interface POS4 0 is up line protocol is up Checksums enabled MTU 4470 Encapsulation PPP ERPDUs enabled min. interval 10msec. RDPDUs enabled min. interval 100msec. Addr Mask enabled Congestion Experienced bit set at 4 packets CLNS fast switching enabled CLNS SSE switching disabled DEC compatibility mode OFF for this interface Next ESH ISH in 38 seconds Routing Protocol IS-IS Circuit Type level-1-2 Interface number 0x0 local circuit ID 0x100 Neighbor Extended Local Circuit ID 0x1 Neighbor System-ID Frankfurt Level-1 IPv6 Metric 10 Number of active level-1 adjacencies 1 Level-2 IPv6 Metric 10 Tools 443 Number of active level-2 adjacencies 1 Next IS-IS Hello in 4 seconds if state UP . IOS .
