Dell Force10 E600i FTOS Version 8.4.1.5 Configuration Guide for ExaScale - Page 500

www.dell.com | support.dell.com Transition Mode All routers in the area or domain must use the same type of IPv6 support, either single-topology or multi-topology. A router operating in multi-topology mode will not recognize the ability of the single-topology mode router to support IPv6 traffic, which will lead to holes in the IPv6 topology. While in transition mode, both types of TLVs (single-topology and multi-topology) are sent in LSPs for all configured IPv6 addresses, but the router continues to operate in single-topology mode (that is, the topological restrictions of the single-topology mode remain in effect). Transition mode stops after all routers in the area or domain have been upgraded to support multi-topology IPv6. Once all routers in the area or domain are operating in multi-topology IPv6 mode, the topological restrictions of single-topology mode are no longer in effect. Interface support MT IS-IS is supported on physical Ethernet interfaces, physical Sonet interfaces, port-channel interfaces (static & dynamic using LACP), and VLAN interfaces. Adjacencies Adjacencies on point-to-point interfaces are formed as usual, where IS-IS routers do not implement Multi-Topology (MT) extensions. If a local router does not participate in certain MTs, it will not advertise those MT IDs in its IIHs and so will not include that neighbor within its LSPs. If an MT ID is not detected in the remote side's IIHs, the local router does not include that neighbor within its LSPs. The local router will not form an adjacency if both routers don't have at least one common MT over the interface. Graceful Restart e Graceful Restart is supported on platforms for both Helper and Restart modes. Graceful Restart is a protocol-based mechanism that preserves the forwarding table of the restarting router and its neighbors for a specified period to minimize the loss of packets. A graceful-restart router does not immediately assume that a neighbor is permanently down and so does not trigger a topology change. Normally, when an IS-IS router is restarted, temporary disruption of routing occurs due to events in both the restarting router and the neighbors of the restarting router. When a router goes down without a Graceful Restart, there is a potential to lose access to parts of the network due to the necessity of network topology changes. IS-IS Graceful Restart recognizes the fact that in a modern router, the control plane and data plane are functionality separate. Restarting the control plane functionality (such as the failover of the active RPM to the backup in a redundant configuration) should not necessarily interrupt data packet forwarding. This behavior is supported because the forwarding tables previously computed by an active RPM have been 500 | Intermediate System to Intermediate System