Routing Information Protocol - An industry-standard (if outdated) Dynamic Routing protocol
Distance Vector IGP based (uses routing-by-rumor logic to learn/share routes)
Uses hop count as its metric. One router = one hop
Bandwidth is not a consideration; every router is a single hop regardless of how fast the interface is.
The maximum hop count is 15 (maximum metric value is therefore 15)
Anything beyond this is considered unreachable! Therefore, RIP cannot be used for large networks!
In reality, RIP is rarely used in real networks anyway. Only real use is in small networks or lab environments due to its simplicity and ease of setup.
Three versions:
RIPv1 and RIPv2, which use IPv4
RIPng (RIP Next Generation), for IPv6
Uses two message types:
Request: To ask RIP-enabled neighbor routers to send their routing table
Response: To send the local router’s routing table to neighboring routers
By default, RIP-enabled routers will share their routing table every 30 seconds
As you might imagine, this can create significant congestion in networks with many routers
RIPv1 vs RIPv2
RIPv1:
only advertises classful addresses (Class A, Class B, Class C)
doesn’t support VLSM, CIDR
doesn’t even include subnet mask information in advertisements (Response messages)
simply assumes a mask based on network range (0-127 - Class A - /8; 128-191 - Class B - /16; 192-223 - Class C - /24 )
due do this limitation, RIPv1 is (effectively) entirely unused in modern networking
messages are broadcast to 255.255.255.255
RIPv2:
supports VLSM, CIDR
includes subnet mask information in advertisements
messages are multicast to 244.0.0.9[^Class-D (multicast) range address]
Configuration
Example CLI inputs for a router with two adjacent network connections (172.16.1.0/28 and 10.0.12.0/30):
router rip //enter RIP configuration
version 2 //set to RIPv2 for subnet support
no auto-summary //advertise the actual network prefix, not a Classful conversion
network 10.0.0.0 //This command is still classful, see below
network 172.16.0.0
network command will automatically convert any address you give it to a Classful address
e.g. 10.0.12.0 would be converted to 10.0.0.0, a Class A network
Hence, no need for a netmask
Tells the router to:
look for interfaces with an IP address that is in the specified range
activate RIP on the interfaces that fall in that range
form adjacencies with connected RIP neighbors
advertise the network prefix of the interface (not the prefix in the network command)
The OSPF and EIGRPnetwork commands operate in the same way
passive interface (interface-id) can be used to set an interface to not receive RIP advertisements. This should be done for any interface that is not connected to a RIP neighbor to reduce unnecessary network traffic.
default-information originate shared the router’s default route with RIP, allowing it to advertise the route to other routers.
maximum paths (number) can be used to change the max. number of paths that will be used for load balancing in ECMP