368 Chapter 6: Routing
Figure 6-5
Advertisements Passing on Serial Link for Subnet 162.11.7.0
In Figure 6-5, the routing updates are sent periodically. There is no requirement to make the
updates flow from C and B at the same time; however, in this case, B and C are sending updates
at the same instant in time. This is not a problem until B advertises an infinite-distance (metric)
route to 162.11.7.0 because the subnet just failed. However, the update from C passes the update
from B on the serial link. Table 6-8 and Table 6-9 show the resulting routing table entries, with
a reference to the metric values.
Table 6-8
Router B Routing Table, After Subnet 162.11.7.0 Failed and Update from Router C Is Received
Group
Outgoing Interface
Next Router
Metric
162.11.6.0
S1
0
162.11.7.0
S1
2
162.11.10.0
S1
162.11.6.2
1
Table 6-9
Router C Routing Table, After Subnet 162.11.7.0 Failed and Update from Router B Is Received
Group
Outgoing Interface
Next Router
Metric
162.11.6.0
S1
0
162.11.7.0
S1
16
162.11.10.0
E0
1
Router A
Router C
162.11.9.0
162.11.5.0
162.11.10.0
162.11.7.0
162.11.8.0
162.11.6.0
Router B
S1
S0
S0
S0
S1
S1
162.11.6.0
162.11.7.0
1
2
162.11.10.0
1
162.11.6.0
162.11.7.0
1
1
162.11.10.0
2
1
1
ch06.fm Page 368 Monday, March 20, 2000 5:11 PM