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  • What is RIP (Routing Information Protocol)?

IPAM glossary

What is RIP (Routing Information Protocol)?

RIP (Routing Information Protocol) is a distance-vector routing protocol that lets routers share reachable networks and choose paths by hop count. It limits paths to 15 hops, treating 16 as unreachable, and routers exchange their routing tables with neighbors at regular intervals.

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RIP (Routing Information Protocol) is a distance-vector routing protocol that enables routers to exchange reachability information and select paths based on hop count, with a maximum network depth of 15 hops before routes are marked unreachable at metric 16. The protocol operates simply with minimal configuration and memory requirements by having routers periodically broadcast their full routing tables to directly connected neighbors every 30 seconds, adding one hop to each metric along the way. While RIP's simplicity made it common in early IP networks, its operational weaknesses—including slow convergence after failures that can take minutes to propagate, lack of authentication in version 1, and inability to consider link speed—have made OSPF and BGP the preferred choices for larger deployments today.

  • RIP version 2 introduces subnet masks, multicast updates, and authentication support as improvements over version 1, addressing some security and scalability concerns outlined in RFC 2453.
  • The protocol’s 15-hop limit fundamentally restricts network size and causes remote subnets to disappear from routing tables even when underlying links remain operational.
  • Convergence delays and potential routing loops can occur when link failures propagate through timeout-based detection rather than immediate topology change notification, leading to intermittent packet loss or circulation for several minutes.

RIP at a glance

AttributeValue
Full nameRouting Information Protocol
CategoryNetwork protocol (distance-vector routing protocol)
Defined inRFC 1058 (RIP version 1), RFC 2453 (RIP version 2), RFC 2080 (RIPng for IPv6)
Protocol and portUDP port 520 for RIP versions 1 and 2; UDP port 521 for RIPng
OSI layerLayer 3 routing function, carried over UDP at layer 4
Primary useExchanging routes and selecting paths by hop count in small networks
Related termsOSPF, BGP, IP address, subnet, routing table

How RIP works

RIP routers build routing tables by exchanging reachability information with directly connected neighbors. Each route carries a metric equal to the number of routers that must be crossed to reach the destination.

  1. Initial advertisement: A router starts with its directly connected networks at a metric of 1 and sends them to neighbors in response messages. It can also send a request to ask neighbors for their full tables.
  2. Table update: A router that receives a route adds one hop to the metric. It installs the route if the destination is new or the metric is lower than the one it already holds.
  3. Periodic exchange: Each router sends its full routing table to its neighbors on a regular timer, which is 30 seconds in the standard. Version 2 uses multicast; version 1 uses broadcast.
  4. Timeout and removal: If updates for a route stop arriving, the route is marked unreachable with a metric of 16 and later removed from the table.

A metric of 16 means unreachable, so the longest usable path is 15 hops. RIP version 2 adds subnet masks, authentication and multicast updates, while RIPng extends the protocol to IPv6. Mechanisms such as split horizon and triggered updates reduce routing loops and slow convergence.

Why RIP matters in enterprise networks

RIP is simple to configure and needs little router memory, which made it common in early IP networks. Its 15-hop limit, as defined in RFC 1058 and RFC 2453, caps the size of any network that relies on it. Sending full tables on a timer also consumes bandwidth as the route count grows.

Convergence is the main operational weakness. Because routers learn about failures through timeouts and neighbor updates, a link failure can take minutes to propagate, and routing loops or counting to infinity can occur while tables disagree. Hop count also ignores link speed, so RIP may prefer a slow two-hop path over a fast three-hop path.

Security needs attention as well. RIP version 1 has no authentication, so any device on the segment can inject false routes and redirect traffic. RIP version 2 supports authentication, but many deployments leave it off. Poorly managed RIP, such as mismatched versions or unfiltered updates, leads to blackholed traffic and unstable routing, so most larger networks use OSPF or BGP instead.

RIP vs Open Shortest Path First (OSPF)

RIP is a distance-vector protocol that picks paths by hop count, while OSPF is a link-state protocol that builds a map of the topology and computes paths with a cost metric. What is OSPF?

AttributeRIPOpen Shortest Path First (OSPF)
Protocol typeDistance vectorLink state
MetricHop countCost, typically based on link bandwidth
Maximum network size15 hopsNo hop limit
Update behaviorSends full routing table on a timerFloods link-state advertisements when topology changes
ConvergenceSlower, can take minutes after a failureGenerally faster
Configuration effortLowHigher, with areas and design planning

RIP vs Enhanced Interior Gateway Routing Protocol (EIGRP)

RIP uses only hop count and full periodic updates, while EIGRP uses a composite metric and sends partial updates only when something changes. What is EIGRP?

AttributeRIPEnhanced Interior Gateway Routing Protocol (EIGRP)
MetricHop countComposite metric based on bandwidth and delay by default
Maximum network size15 hopsMuch larger, with a configurable maximum hop count
UpdatesFull table on a timerPartial updates triggered by changes
Loop preventionSplit horizon, hold-down and route poisoningDiffusing update algorithm

Common RIP issues

When a link fails, routers learn of it through timeouts or neighbor updates, so traffic can be dropped or looped for minutes. Engineers often see this as intermittent reachability that clears only after route timers expire.

Networks deeper than 15 routers lose routes because a metric of 16 means unreachable. Remote subnets disappear from the table even though the links are up.

RIP version 1 does not carry subnet masks, while RIP version 2 does. Mixing them, or running version 1 on a network using variable-length subnets, causes missing or wrong routes.

If split horizon or poisoning is disabled, routers can keep advertising a dead route to each other and raise its metric slowly until it reaches 16. Packets circulate in the meantime.

Full table updates on every timer interval consume noticeable bandwidth on low-speed WAN links when route counts are large. Interface utilization shows regular bursts at each update.

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RIP FAQ

Related terms

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Open Shortest Path First (OSPF)

A routing protocol for IP networks that uses a link state routing algorithm and falls into the group of interior gateway protocols, operating within a single autonomous system.

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Enhanced Interior Gateway Routing Protocol (EIGRP)

An advanced distance-vector routing protocol that is used on a computer network for automating routing decisions and configuration.

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BGP (Border Gateway Protocol)

A standardized exterior gateway protocol to exchange routing and reachability information among autonomous systems on the internet.

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User Datagram Protocol (UDP)

An alternative protocol to TCP used primarily for establishing low-latency and loss-tolerating connections between applications on the internet.

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CIDR (Classless Inter-Domain Routing)

A method for allocating IP addresses and IP routing introduced by the ITEF 1993 to replace classful networks.

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Classful networks

A previous network addressing architecture that divided the IP address space for IPv4 into five address classes based on the leading four address bits.

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Subnet mask

A 32-bit number that masks an IP address, and divides the IP address into network address and host address.

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Multicast

Group communication where data transmission is addressed to a group of destination computers simultaneously.

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