Use the Routing Protocol > RIP > Distance (Add) page to configure the send/recieve version, authentication settings, and the loopback prevention method for each interface that participates in the RIP routing process.
Command Usage
Specifying Receive and Send Protocol Types -
Specify the protocol message type accepted (that is, RIP version) and the message type sent (that is, RIP version or compatibility mode) for each RIP interface.
Setting the RIP Receive Version or Send Version for an interface overrides the global setting specified in the RIP General Settings screen.
The Send Version can be specified based on these options:
Use "RIPv1" or "RIPv2" if all routers in the local network are based on RIPv1 or RIPv2, respectively.
Use "RIPv1 Compatible" to propagate route information by broadcasting to other routers on the network using the RIPv2 advertisement list, instead of multicasting as normally required by RIPv2. (Using this mode allows older RIPv2 routers which only receive RIP broadcast messages to receive all of the information provided by RIPv2, including subnet mask, next hop and authentication information. (This is the default setting.)
Use "Do Not Send" to passively monitor route information advertised by other routers attached to the network
The Receive Version can be specified based on these options:
Use "RIPv1" or "RIPv2" if all routers in the local network are based on RIPv1 or RIPv2, respectively.
Use "RIPv1 and RIPv2" if some routers in the local network are using RIPv2, but there are still some older routers using RIPv1. (This is the default setting.)
Use"Do Not Receive" if dynamic entries are not required to be added to the routing table for an interface. (For example, when only static routes are to be allowed for a specific interface.)
Protocol Message Authentication -
RIPv1 is not a secure protocol. Any device sending protocol messages from UDP port 520 will be considered a router by its neighbors. Malicious or unwanted protocol messages can be easily propagated throughout the network if no authentication is required.
RIPv2 supports authentication using a simple password or MD5 key encryption. When a router is configured to exchange authentication messages, it will insert the password into all transmitted protocol packets, and check all received packets to ensure that they contain the authorized password. If any incoming protocol messages do not contain the correct password, they are simply dropped.
For authentication to function properly, both the sending and receiving interface must be configured with the same password or authentication key.
Loopback Prevention -
Just as Layer 2 switches use the Spanning Tree Algorithm to prevent loops, routers also use methods for preventing loops that would cause endless retransmission of data traffic. When protocol packets are caught in a loop, links will be congested, and protocol packets may be lost. However, the network will slowly converge to the new state. RIP supports several methods which can provide faster convergence when the network topology changes and prevent most loops from occurring.
Command Parameters
Layer 3 VLAN interface. This interface must be configured with an IP address and have an active link. (Range: 1-4093)
The RIP version to send on an interface.
RIPv1: Sends only RIPv1 packets.
RIPv2: Sends only RIPv2 packets.
RIPv1 Compatible: Route information is broadcast to other routers with RIPv2.
Do Not Send: Does not transmit RIP updates. Passively monitors route information advertised by other routers attached to the network.
The default depends on the setting for the Global RIP Version. configured on the Routing Protocol > RIP > General page.
The RIP version to receive on an interface.
RIPv1: Accepts only RIPv1 packets.
RIPv2: Accepts only RIPv2 packets.
RIPv1 or RIPv2: Accepts RIPv1 or RIPv2 packets.
Do Not Receive: Does not accept incoming RIP packets. This option does not add any dynamic entries to the routing table for an interface.
The default depends on the setting for the Global RIP Version. configured on the Routing Protocol > RIP > General page.
Specifies the type of authentication required for exchanging RIPv2 protocol messages. (Default: No Authentication)
No Authentication: No authentication is required.
Simple Password: Requires the interface to exchange routing information with other routers based on an authorized password. (Note that authentication only applies to RIPv2.)
MD5: Message Digest 5 (MD5) authentication.
MD5 is a one-way hash algorithm is that takes the authentication key and produces a 128 bit message digest or "fingerprint." This makes it computationally infeasible to produce two messages having the same message digest, or to produce any message having a given pre-specified target message digest.
Specifies the key to use for authenticating RIPv2 packets. For authentication to function properly, both the sending and receiving interface must use the same password. (Range: 1-16 characters, case sensitive)
Specifies the method used to reduce the convergence time when the network topology changes, and to prevent RIP protocol messages from looping back to the source router.
Split Horizon - This method never propagate routes back to an interface from which they have been acquired.
Poison Reverse - This method propagates routes back to an interface from which they have been acquired, but sets the distance-vector metrics to infinity. This provides faster convergence. (This is the default setting.)
None - No loopback prevention method is employed. If a loop occurs without using any prevention method, the hop count for a route may be gradually incremented to infinity (that is, 16) before the route is deemed unreachable.