Have a look at rfc 1058. It explains how this limitation can be remedy:
https://www.ietf.org/rfc/rfc1058.txt
shouldn't be any bigger than required. Thus the choice of infinity
is a tradeoff between network size and speed of convergence in case
counting to infinity happens. The designers of RIP believed that the
protocol was unlikely to be practical for networks with a diameter
larger than 15.
There are several things that can be done to prevent problems like
this. The ones used by RIP are called "split horizon with poisoned
reverse", and "triggered updates".
2.2.1. Split horizon
Note that some of the problem above is caused by the fact that A and
C are engaged in a pattern of mutual deception. Each claims to be
able to get to D via the other. This can be prevented by being a bit
more careful about where information is sent. In particular, it is
never useful to claim reachability for a destination network to the
neighbor(s) from which the route was learned. "Split horizon" is a
scheme for avoiding problems caused by including routes in updates
sent to the gateway from which they were learned. The "simple split
horizon" scheme omits routes learned from one neighbor in updates
sent to that neighbor. "Split horizon with poisoned reverse"
includes such routes in updates, but sets their metrics to infinity.
If A thinks it can get to D via C, its messages to C should indicate
that D is unreachable. If the route through C is real, then C either
has a direct connection to D, or a connection through some other
gateway. C's route can't possibly go back to A, since that forms a
loop. By telling C that D is unreachable, A simply guards against
the possibility that C might get confused and believe that there is a
route through A. This is obvious for a point to point line. But
consider the possibility that A and C are connected by a broadcast
network such as an Ethernet, and there are other gateways on that
network. If A has a route through C, it should indicate that D is
unreachable when talking to any other gateway on that network. The
other gateways on the network can get to C themselves. They would
never need to get to C via A. If A's best route is really through C,
no other gateway on that network needs to know that A can reach D.
This is fortunate, because it means that the same update message that
is used for C can be used for all other gateways on the same network.
Thus, update messages can be sent by broadcast.
In general, split horizon with poisoned reverse is safer than simple
split horizon. If two gateways have routes pointing at each other,
advertising reverse routes with a metric of 16 will break the loop
immediately. If the reverse routes are simply not advertised, the
erroneous routes will have to be eliminated by waiting for a timeout.
However, poisoned reverse does have a disadvantage: it increases the
HTH
