H3C S5120-EI Series Configuration Manual

Also see for S5120-EI Series: Installation manual Configuration guide Configuration guide Operation manual Configuration guide

Contents

H3C S5120-EI Series Configuration Manual Manual pdf 9 page image

9IP routing overviewRoutingRouters are responsible for forwarding data packets along networks. Upon receiving a packet, a routerdetermines the optimal path based on the destination address. When the packet reaches the last router inthe path, it then forwards the packet to the intended destination host.Routing provides the path information for guiding the forwarded packets.The term router in this document refers to a router in a generic sense or a Layer 3 switch.Routing table and FIB tableRouting tableThe routing table plays a key role in route selection while the FIB table plays a key role in packetforwarding. Each router maintains a routing table and a FIB table.Routes in a routing table can be divided into the following categories by origin:• Direct routes: Routes discovered by data link protocols, also known as interface routes.• Static routes: Routes that are manually configured.• Dynamic routes: Routes that are discovered dynamically by routing protocols.Dynamic routing protocol is not supported on the S5120-EI Series Ethernet Switches.Each entry in the FIB table specifies the physical interface to which a packet should travel: the next hop(the next router), or directly to its intended destination.Introduction to routing tableEach router maintains a local routing table, and each routing protocol maintains a protocol routing table.• Protocol routing table:A protocol routing table stores routes discovered by the routing protocol.A routing protocol can redistribute and advertise routes generated by other protocols. For example,OSPF can redistribute direct routes, static routes, and IS-IS routes to the OSPF routing table, and thenadvertise those routes.• Local routing table:A local routing table stores the routes found by all protocols and delivers the optimal routes to theFIB table to guide packet forwarding. The optimal route selection is based on the routing protocolpreferences and route metrics.