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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.
– 783 –
C
20
HAPTER
Configuring the Routing Information Protocol
| Unicast Routing
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