16.0.0. This leads to confusion when routing across network 192.168.14.0. In this
example, Router C receives routes about 172.16.0.0 from two different directions, so it cannot
make a correct routing decision.
Figure 3-36 Classful Summarization in Discontiguous Networks
You can resolve this situation by using RIP-2, OSPF, IS-IS, or EIGRP and not using
summarization because the subnet routes would be advertised with their actual subnet masks. For
example:
Summary of Implementing Variable-Length Subnet Masks
The following list summarizes the key points discussed in this section:
?– Subnetting lets you ef?¬?ciently allocate addresses by taking one large broadcast domain and
breaking it up into smaller, more manageable broadcast domains.
NOTE Cisco IOS Software also provides an IP unnumbered feature that permits
discontiguous subnets to be separated by an unnumbered link.
C
RIPv1 will advertise
network 172.16.0.0.
B
RIPv1 will advertise
network 172.16.0.0.
172.16.5.0
255.255.255.0
192.168.14.16
255.255.255.240
172.16.6.0
255.255.255.0
A
Review Questions 133
?– VLSMs let you more ef?¬?ciently allocate IP addresses by adding multiple layers of the
addressing hierarchy.
Pages:
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217