• The T3 timer sets the overall wait time after which the router determines that it has failed to achievedatabase synchronization (by setting the overload bit in its own LSP). You can base this timer onadjacency settings with the value derived from adjacent routers that are engaged in graceful restartrecovery (the minimum of all the Remaining Time values advertised by the neighbors) or by setting aspecific amount of time manually.Implementation InformationIS-IS implementation supports one instance of IS-IS and six areas.You can configure the system as a Level 1 router, a Level 2 router, or a Level 1-2 router. For IPv6, the IPv4implementation has been expanded to include two new type, length, values (TLVs) in the PDU that carryinformation required for IPv6 routing. The new TLVs are IPv6 Reachability and IPv6 Interface Address.Also, a new IPv6 protocol identifier has also been included in the supported TLVs. The new TLVs use theextended metrics and up/down bit semantics.Multi-topology IS-IS adds TLVs:• MT TLV — contains one or more Multi-Topology IDs in which the router participates. This TLV isincluded in IIH and the first fragment of an LSP.• MT Intermediate Systems TLV — appears for every topology a node supports. An MT ID is added tothe extended IS reachability TLV type 22.• MT Reachable IPv4 Prefixes TLV — appears for each IPv4 an IS announces for a given MT ID. Itsstructure is aligned with the extended IS Reachability TLV Type 236 and it adds an MT ID.• MT Reachable IPv6 Prefixes TLV — appears for each IPv6 an IS announces for a given MT ID. Itsstructure is aligned with the extended IS Reachability TLV Type 236 and add an MT ID.By default, Dell Networking OS supports dynamic host name exchange to assist with troubleshooting andconfiguration. By assigning a name to an IS-IS NET address, you can track IS-IS information on thataddress easier. Dell Networking OS does not support ISO CLNS routing; however, the ISO NET format issupported for addressing.To support IPv6, the Dell Networking implementation of IS-IS performs the following tasks:• Advertises IPv6 information in the PDUs.• Processes IPv6 information received in the PDUs.• Computes routes to IPv6 destinations.• Downloads IPv6 routes to the RTM for installing in the FIB.• Accepts external IPv6 information and advertises this information in the PDUs.The following table lists the default IS-IS values.Table 43. IS-IS Default ValuesIS-IS Parameter Default ValueComplete sequence number PDU (CSNP) interval 10 secondsIS-to-IS hello PDU interval 10 secondsIS-IS interface metric 10Metric style NarrowDesignated Router priority 64Intermediate System to Intermediate System 473
