HP 600 Series, Services And Applications

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Alternatively, the central-site switched circuits may be configured with
individual phone numbers. Remote sites (under V.25 bis control) would then
have several possible numbers to dial to get around busy conditions.
Switched-circuit-only networks can be a very cost-effective alternative when
used for several hours or less each day. To ensure that the switched circuit is
open (connected) for the minimum possible amount of time, it is essential to
disable the dynamic routing protocols (RIP and OSPF) and configure
static
routes. Dynamic routing protocols generate periodic traffic that will hold
switched circuits open permanently!
N o t e
Pool circuits may be used only with IP protocol.
NxN Backup
NxN backup refers to a configuration in which every leased-line circuit has
its own dedicated backup circuit, for example, in a central site. Dedicated
backup circuits are provided using the
backup circuit type. Either manual
adapters or V.25 bis adapters can be used to provide the backup circuits.
Consider the network shown in figure 12. Each leased line has a dedicated
backup. When link 1 fails, R
b
dials R
a1
(or vice versa). When link 2 fails, R
c
dials R
a2
. A backup circuit is required for each leased line.
Figure 12. NxN Backup for Leased-Line Network
a1 a2
b c
Circuit
Switching
Network
Link 2
Link 1
Improving Network Availability
Sample Networks
3-24