range is also within the reserved LAN subnet address range and must not be
assigned.
The rule is to avoid assigning addresses within the reserved address ranges
given by the subnet mask with the fewest number of bits in the subnet ID
field. In figure 5 the subnet mask with the fewest number of bits in the
subnet ID is 255.255.255.0. Thus the reserved address ranges are 170.200.0.0
through 170.200.0.255 and 170.200.255.0 through 170.200.255.255.
Addressing Flexibility
OSPF enhances IP addressing flexibility by allowing IP networks to be parti-
tioned. Network partitioning is not permissible with RIP. A network becomes
partitioned when one or more subnets of a network become separated from
the other subnets of the same network by a second network. In figure 6, the
class B network 128.1.x.x is partitioned by network 192.1.1.x.
Figure 6. A Partitioned Network
To understand why network partitioning might be useful, refer again to
figure 6. Suppose network 128.1.x.x is a large network with very few
remaining subnets. Subnets of the class C network 192.1.1.x can be used for
synchronous links so that none of the remaining class B subnets have to be
used to extend the network.
Another situation in which support for partitioned networks is helpful is
when networks are combined as a result of a merger or acquisition.
Networks often overlap in this case, often resulting in capacity imbalances.
Being able to partition a network allows the network’s administrators much
more flexibility in assembling the combined networks.
128.1.1.x
128.1.2.x
192.1.1.x
ROUTER
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Routing with OSPF
Addressing Flexibility
3-81
Содержание 600 Series
Страница 1: ...Hewlett Packard Series 200 400 and 600 Routers HP Routing Services and Applications ...
Страница 4: ......
Страница 5: ...1 Product Notes ...
Страница 6: ...Features of HP Routers Architecture and Technology Branch Office Routing Product Notes 1 2 ...
Страница 38: ...Architecture and Technology Software Control Path Architecture 1 34 ...
Страница 52: ...Branch Office Routing Future Directions 1 48 ...
Страница 53: ...2 Routing Services Notes ...
Страница 106: ...Bridging Service Traffic Prioritization 2 54 ...
Страница 158: ...Novell IPX Routing Service NetBIOS Protocol Support 2 106 ...
Страница 194: ...Data Compression for WAN Links Conclusion 2 142 ...
Страница 195: ...3 Application Notes and Case Studies ...
Страница 224: ...Improving Network Availability Application Recovery 3 30 ...
Страница 234: ...ISDN Wide Area Network Design Dry Creek Joint Elem School District Performance 3 40 ...
Страница 316: ......