If routing table contains an active default route, then routing table lookup in this table will never fail.Ĭonnected routes are created automatically for each IP network that has at least one enabled interface attached to it (as specifie in the /ip address configuration). Route with dst-address 0.0.0.0/0 applies to every destination address. There are different groups of routes, based on their origin and properties. Routing tables are referenced by their name, and are created automatically when they are referenced in the configuration.Įach routing table can have only one active route for each value of dst-address IP prefix. Routes can be assigned to specific routing table by setting their routing-mark property to the name of another routing table. Policy routing is implemented as a list of policy routing rules, that select different routing table based on destination address, source address, source interface, and routing mark (can be changed by firewall mangle rules) of the packet.Īll routes by default are kept in the main routing table. When forwarding decision uses additional information, such as a source address of the packet, it is called policy routing. This route is installed into FIB and marked as active. If routing table contains several routes with the same dst-address, only one of them can be used to forward packets. This operation (finding the most specific route that matches given address) is called routing table lookup. If there are several routes that apply to a particular IP address, the most specific one (with largest netmask) is used. Each route has dst-address property, that specifies all destination addresses this route can be used for. RIB is used to filter routing information, calculate best route for each destination prefix, build and update Forwarding Information Base and to distribute routes between different routing protocols.īy default forwarding decision is based only on the value of destination address. RIB (Routing Information Base) contains complete routing information, including static routes and policy routing rules configured by the user, routing information learned from routing protocols, information about connected networks. The main table is also used for nexthop lookup. These tables are used for best route selection. All routes without routing-mark are kept in the main routing table. RIB contains routes grouped in separate routing tables based on their value of routing-mark.BGP does not have internal routing tables and stores complete routing information from all peers in the RIB. This is where per-protocol routing decisions are made. Each routing protocol (except BGP) has it's own internal tables.It contains a copy of the necessary routing information. FIB (Forwarding Information Base), that is used to make packet forwarding decisions.Router keeps routing information in several separate spaces: 2.6 Criteria for selecting candidate routes.
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