![]() ![]() RIP advertisement packets are only 512 bytes in length and can contain a maximum of 25 different routing table entries, so a large routing table with hundreds of entries means that dozens of RIP packets are broadcast every 30 seconds. Its main disadvantage is that the routing table of a RIP-enabled router can be quite large because it contains all possible routes to all possible networks. RIP is a well-supported industry standard routing protocol. If you try to send a packet to a network more than 15 hops away, a RIP router returns an Internet Control Message Protocol ( ICMP) Destination Unreachable message. RIP metrics are independent of TCP/IP Time to Live ( TTL) values, so if two networks are separated by more than 15 routers on a RIP-enabled internetwork, packets sent between them are dropped even if their TTL values have not decremented to zero. This limits RIP implementation to small and mid-sized internetworks. RIP supports a maximum metric of 15 networks that are more than 15 hops away are unreachable using RIP. In addition, the new RIP router announces to its neighbors all network IDs of locally attached networks so that they can update their routing tables with this information. ![]() These RIP advertisements from neighboring RIP routers allow the router to build its own routing tables. When a RIP router is first turned on, it announces its presence using a General RIP Request message so that neighboring RIP routers can send it advertisements of their routing tables. If a routing table has multiple routes for a single network ID, RIP stores the route with the lowest metric (number of hops to destination). You might assume that this adds a lot of overhead to network traffic, but this information is broadcast information and is thus propagated only throughout the local network and received only by routers that have a routing interface to the local network. RIP-enabled routers on a TCP/IP internetwork broadcast their complete routing tables every 30 seconds over User Datagram Protocol (UDP) port 520 using RIP advertisements. The routing table of a RIP router contains the cost in hops of every path to every destination network on the internetwork. RIP routers do not use other routing metrics such as load, bandwidth, latency, or Maximum Transmission Unit (MTU) in calculating routing costs. Routing tables in RIP-enabled routers are calculated on the basis of the number of hops to the destination network. RIP is designed for intradomain routing (routing within a flat routing space or routing domain). RIP has been implemented for both TCP/IP and IPX/SPX internetworks as RIP for IP and RIP for IPX, respectively. RIP is based on the distance vector routing algorithm, one of several common routing algorithms that routers use to dynamically calculate the cost or metric of each possible path through an internetwork. ![]()
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