Dell Force10 E1200i FTOS Version 8.4.1.5 Configuration Guide for ExaScale - Page 501

downloaded into the Forwarding Information Base on the line cards (the data plane) and are still resident. For packets that have existing FIB/CAM entries, forwarding between ingress and egress ports can continue uninterrupted while the control plane IS-IS process comes back to full functionality and rebuilds its routing tables. A new TLV (the Restart TLV) is introduced in the IIH PDUs, indicating that the router supports Graceful Restart. Timers Three timers are used to support IS-IS Graceful Restart functionality. Once Graceful Restart is enabled, these timers manage the the Graceful Restart process. • The T1 timer specifies the wait time before unacknowledged restart requests are generated. This is the interval before the system sends a Restart Request (an IIH with RR bit set in Restart TLV) until the CSNP is received from the helping router. The duration can be set to a specific amount of time (seconds) or a number of attempts. • The T2 timer is the maximum time that the system will wait for LSP database synchronization. This timer applies to the database type (level-1, level-2 or both). • The T3 timer sets the overall wait time after which the router determines that it has failed to achieve database synchronization (by setting the overload bit in its own LSP). This timer can be based on adjacency settings with the value derived from adjacent routers that are engaged in graceful restart recovery (the minimum of all the Remaining Time values advertised by the neighbors) or by setting a specific amount of time manually. Implementation Information IS-IS implementation supports one instance of IS-IS and six areas. The system can be configured as a Level 1 router, a Level 2 router, or a Level 1-2 router. For IPv6, the IPv4 implementation has been expanded to include two new type-length-values (TLV) in the protocol data unit (PDU) that carry information 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 the extended metrics and up/down bit semantics. Multi-Topology IS-IS adds TLVs: • The Multi-Topology TLV contains one or more Multi-Topology IDs in which the router participates. This TLV is included in IIH and the first fragment of an LSP. • The MT Intermediate Systems TLV appears for every topology a node supports. An MT ID is added to the extended IS reachability TLV type 22. • The Multi-Topology Reachable IPv4 Prefixes TLV appears for each IPv4 announced by an IS for a given MT ID. Its structure is aligned with the extended IS Reachability TLV Type 236 and it adds an MT ID. • The Multi-Topology Reachable IPv6 Prefixes TLV appears for each IPv6 announced by an IS for a given MT ID. Its structure is aligned with the extended IS Reachability TLV Type 236 and add a MT ID. Intermediate System to Intermediate System | 501