Rib fib ARP Fdb

The difference between 1.RIB and fib:

RIB: Routing Table

FIB: Forwarding Information table

The FIB table is more of a router that needs to be forwarded quickly, and the routing table entries on such routers usually reach tens of thousands, and if the routing table is traditionally retrieved in a way that is very inefficient in forwarding, the FIB table appears as a streamlined form of the routing table, usually only for commonly used table entries. When a route is required, the FIB table is retrieved first, and the routing table is retrieved if it is not found.

In most routers, rib behaves as a routing table, and the FIB behaves as a cache form, which is a subset of the routing table and is generated by the routing table.

In general, FIB is a data structure organized for high-speed lookups (rather than simply copying the contents of the routing table, data storage and retrieval methods, etc.) that are different from the composition of the routing table.

RIB is a word: all, know how to go all the place, but slow.

FIB is a word: fast, just know how to walk the road, fast.

If it is a distributed device, usually the FIB distributed on the LPU, by the LPU on the CPU to implement a quick route, if the LPU can not find the road, only to the MPU processing, the rib here to save the most complete routing information, can provide the less common route selection results.

Differences between the 2.ARP table and the FDB table:

ARP table: The correspondence between IP and Mac;

FDB table: The correspondence between Mac+vlan and port;

The two biggest difference is that ARP is a three-tier forwarding, and FDB is used for two-tier forwarding. In other words, even if the two devices are not a network segment or no IP at all, as long as the link between the two layers is connected, you can pass the FDB table for data Forwarding!

The main function of the FDB table is to switch to the two-layer routing, just imagine, if there is only ARP table, no fdb table, it is like only know the place name and direction, and do not know which way to reach the destination, equipment is not working properly. The purpose of the FDB table is to tell the device to go out on a certain port and get to a destination Mac.

So how did the Fdb form? Very simply, the switch extracts the entries in the Fdb table, such as the source Mac, VLAN, and the port that receives the data frame, when the data frame is received. The next time a message is sent to the Mac in that VLAN, it is OK to drop it directly from that port.

Of course, the FDB table and the ARP table have an aging time.

Rib fib ARP Fdb