and Router A, as shown in Step 1 of Figure 6-7. Router A happens to send its next update out
its S1 interface to Router B just before it hears the bad news about 162.11.10.0 from Router C,
as denoted as Step 2 in Figure 6-7. Table 6-10 shows the result of these two updates entering
Router B.
update, the router does not advertise subnet 162.11.10.0 out S0 due to split horizon rules, but
Router B advertises 162.11.10.0 to Router C out Serial1. Router C incorrectly believes that the
route to 162.11.10.0 exists through Router B; Router C also tells Router A that it has a route to
162.11.10.0. So, counting to infinity occurs.
route to 162.11.10.0 pointed to Router C. It was then changed to point to Router A. Holddown
would require Router B to wait for a period to learn new routes after an old one has failed, in
this case ignoring the metric 2 route learned from Router A.
information about that subnet for a time equal to the holddown timer.
Figure 6-7. During the same time, Routers C and A both would be advertising infinite metric
routes to 162.11.10.0 to Router B, which also would quickly be receiving only routing updates
for 162.11.10.0 with an infinite metric.
and typically does--define a maximum usable metric value, with any number over that being
considered infinite.)