Routing Information Protocol
Operating at the OSI model’s Network layer, the Routing Information system (RIP) is an earlier, fundamental distance-vector routing system. Its main objective is to assist routers in figuring out the most efficient way to transport data packets throughout a network inside of a single Autonomous System (AS). Particularly in small networks, Routing Information Protocol is known for being easy to set up and utilize.
History and Development
Routing Information Protocol was initially created as GWINFO in 1981 as part of the Xerox PARC Universal Protocol protocol suite by Xerox Network Systems (XNS). In 1988, it was formally specified in RFC 1058. When RIP was added to the routed daemon in the 1982 Berkeley Software Distribution of the UNIX operating system, it was widely used.
How RIP Works
A distance-vector technique is used by Routing Information Protocol to choose the routes that packets should take to get to their destinations. Because routers only know the routes that their neighbours who are directly linked to them tell them, they are unable to fully understand the network architecture, which is why this technique is frequently referred to as “routing by rumour.”
This procedure entails:
Hop Count as Metric: Hop count is the only routing metric used by Routing Information Protocol to identify the optimal path. Between the source and destination networks, a packet must pass through a certain number of routers, which is known as the hop count. A route is deemed optimal if it has the fewest number of hops.
Routing Table Maintenance: A routing table that contains a list of all reachable networks and the number of hops needed to get there is kept up to date by each Routing Information Protocol router.
Periodic Updates: On a regular basis, routers broadcast their complete routing tables to neighbouring routers that are directly connected. These updates happen by default every 30 seconds.
Convergence: These updates are sent to nearby routers, who then adjust their own routing tables appropriately. Until convergence is reached, all Routing Information Protocol hosts in the network will have the same understanding of the routing paths.
Path Selection: When a router receives a route update, it modifies its table entry if the new path is shorter. Before updating the table, if the new path is longer, it goes into a “hold-down” phase to look for any fresh changes.
Unreachable Networks: Routing Information Protocol deems a network more than 15 hops away as unreachable. With a hop count of 16, unreachability is indicated.
Route Stability: When six consecutive update cycles (180 seconds) pass without an update to a routing table item, the Routing Information Protocol router eliminates that route and alerts the rest of the network.
Key Features and Characteristics
- Open Standard: RIP is not a Cisco-exclusive protocol; it is an open standard.
- OSI Model Layer: According to the OSI model, it functions at the Network layer.
- Administrative Distance (AD): RIP uses 120 as its Administrative Distance (AD) value by default. A lower AD denotes greater reliability.
- UDP Port: UDP port 520 is the transport protocol used by RIP. RIPng utilizes port 521 on UDP.
- Load Balancing: In order to distribute network traffic evenly among routes with the same hop count as equal-cost paths, Routing Information Protocol enables equal-cost load balancing. It can load balance across up to six customizable equal-cost links by default.
- Loop Prevention: RIP uses techniques including hold-down timers, route poisoning, and split horizon to avoid routing loops.
- Hold-down timers: Avoid having a previously downed route reinstated by incorrect updates.
- Split horizon: Stops a router from broadcasting a route back out of the interface from whence it received it.
- Poison reverse updates: A network is marketed with a metric of 16 to indicate inaccessibility when it becomes unavailable.
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RIP Protocol Versions
RIP comes in three primary versions:
RIP Version 1 (RIPv1)
- Defined in RFC 1058.
- Classful routing assumes default masks for IP classes automatically and does not transmit subnet mask information in its routing updates. Variable Length Subnet Masking (VLSM) and Classless Inter-Domain Routing (CIDR) are therefore incompatible with it.
- 255.255.255.255 receives broadcasts of routing updates.
- It is susceptible to security risks because it does not support authentication.
- Enables IPv4 networks.
RIP Version 2 (RIPv2)
- Defined in RFC 2453.
- A classless routing technology that supports VLSM and CIDR by incorporating subnet mask information into its updates.
- Updates using the multicast address 224.0.0.9, which lowers network bandwidth in comparison to RIPv1 broadcasts.
- Incorporates MD5 authentication into safe routing conversations.
- Allows for the filtering and redistribution of routes using route tags.
- Enables IPv4 networks.
RIP Next Generation (RIPng)
- Defined in RFC 2080.
- Designed with IPv6 networks in mind.
- Similar to its predecessors, it sends updates every 30 seconds and has a 15-hop restriction.
- Updates are sent over multicast to FF02::9.
- Subnet information and classless routing support.
- Maintains MD5 authentication for security (albeit IPsec was supposed to be used for authentication on IPv6 routers).
- Uses UDP port 521 for operation.
RIP Message Format
The fields listed below are included in a Routing Information Protocol message:
- Command: It is utilized for both requests and responses. The field is 8 bits in size. While the response is represented by 1, the request is represented by
- Version: Version denotes the current RIP protocol version. Assuming we utilize version 1 of the protocol, we input 1 in this field.
- Reserved: 0 denotes that the field is a reserved field.
- Family: This field is 16 bits in size. Given that we utilize the TCP/IP protocol, we entered 2 in this box.
- Network Address: It is a field with 14 bytes. We utilize IPv4, which fills in 4 bytes, therefore the remaining 10 bytes are zero.
- Distance: This parameter represents the number of routers needed to reach the destination network, often known as the hope count.
RIP Timers
To regulate its performance, RIP makes use of multiple timers:
Update Timer: The frequency of routing updates is this. IP RIP delivers a full copy of its routing database every 30 seconds, subject to split horizon. This is done every 60 seconds via Internetwork Packet Exchange Routing Information Protocol.
Invalid Timer: This is when a route update does not include updated content. Before marking a route as invalid, RIP waits 180 seconds and then promptly places it on hold-down.
Hold-down Timer: This helps ensure route stability in a Cisco setting. Regular update messages are prevented from unnecessarily creating a routing loop by hold-downs. The router waits a certain amount of time before acting on fresh information that isn’t superior. RIP has a 180-second hold-down period.
Flush Timer: When a route doesn’t respond, the item will be deleted from the routing table. It’s set to 240 seconds. Compared to the invalid timer, this one is 60 seconds longer and begins after the route has been deemed invalid. The times can be adjusted.
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Configuration
Configuring Routing Information Protocol is relatively easy. Once IP addresses are assigned to interfaces, the router rip command enables the protocol. Then, the network command specifies the directly connected networks to be advertised. The version command (e.g., version 2) specifies the RIP version, and no auto-summary disables auto-summarization for classless routing. For IPv6, RIPng uses interface-specific commands like ipv6 rip MYRIP enable instead of network statements.
Verification and Troubleshooting Commands
A number of Cisco IOS instructions are necessary for Routing Information Protocol verification and troubleshooting:
show ip protocols: All IP routing protocols set up on the router are shown by this command, along with the RIP version being sent and received, configured networks, interfaces taking part in Routing Information Protocol updates, and RIP update timings.
show ip route: Used for viewing the IP routing table on the router. To the left of the route item is a “R” that denotes RIP-learned routes.
debug ip rip: With this command, the router’s console shows real-time RIP routing updates as they are transmitted and received. Discontiguous subnets and duplicate networks are among the problems it can assist in diagnosing. Routes that are advertised with a metric of 16 are considered inaccessible.
show ip rip database: This command, when triggered extensions to RIP are enabled, shows the contents of the RIP private database.
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Security Concerns
Routing Information Protocol contains several security flaws:
Routing Table Spoofing: Incorrect routing updates sent by malicious routers may result in traffic redirection, instability, or routing loops.
Sniffing and Eavesdropping: Since RIP updates are transmitted in plain text, network topology can be easily deduced by unauthorized parties that intercept and interpret them.
Denial of Service (DoS) Attacks: A network collapse or loss of service may result from congestion and instability brought on by flooding bogus routing updates.
Lack of Authentication and Authorization: Due to its absence of authentication, RIPv1 leaves the network vulnerable to intrusion and access threats by permitting unauthorized routers to take part in routing operations. Both RIPng and RIPv2 allow authentication.
Advantages of Routing Information Protocol
Simplicity: Few parameters are needed, making it simple to comprehend, set up, and administer.
Low Resource Requirements: Less CPU and memory intensive than other protocols, making it appropriate for devices with constrained processing capabilities.
Compatibility: Practically all routers support it, and it works with a wide range of devices and operating systems.
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Disadvantages of RIP
Notwithstanding its ease of use, RIP has serious drawbacks that render it less appropriate for large, contemporary networks:
Limited Scalability: Large or complicated networks cannot use it because to its 15-hop constraint.
Slow Convergence: Causes routing loops, black holes, and network instability since it takes a long time to notice changes in the network (such as a connection going down) and for all routers to have a consistent view. This is frequently referred to as the “count-to-infinity” problem.
High Network Overhead/Bandwidth Inefficiency: It uses a lot of bandwidth to send complete routing tables every 30 seconds, which could lead to congestion and packet loss.
Limited Metric: Only takes into account the number of hops, ignoring other crucial elements like bandwidth, link speed, and dependability. This may result in less-than-ideal routing, when a slower but shorter route is selected instead of a longer, faster one.
Lack of Modern Features: Does not support VPN, MPLS, encryption, or full IPv6 support (in RIPv1/v2), or advanced features like authentication (in RIPv1).
Modern Usage
Because of its drawbacks, RIP is not as often used in contemporary network environments as more sophisticated and scalable protocols like Enhanced Interior Gateway Routing Protocol (EIGRP), Border Gateway Protocol (BGP), or Open Shortest Path First (OSPF). Nevertheless, it can still be found in:
- Networks of modest to moderate size where configuration simplicity and ease are valued.
- Networks that are legacy and have not been updated.
- Basic routing ideas can be learnt in lab settings or classroom settings.
- As a redundant or backup routing system in specific situations.
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