HP 200 Series Services And Applications page 220

Improving Network Availability
Sample Networks
The network in figure 13 is set up as follows:
The leased lines and Ethernet LANs are configured normally.
The switched circuits at the remote sites can use manual or V.25 bis
adapters that can be configured to connect when the "circuit is
enabled" or when "data is available". The use of V.25 bis adapters
configured to connect when "data is available or on incoming call" is
preferred since it provides the most flexibility and control. The
switched circuits are configured as primary circuits (circuit group
members).
The switched circuits at the central site must use V.25 bis adapters
and must be configured to connect when "data is available or on
incoming call". These circuits must be configured as pool circuits
(pool circuit group members). Additionally, IP pool circuit map
entries must be configured (to map IP addresses to phone numbers).
Switched circuits must be configured using static routes. Each
leased line is favored over its switched counterpart by ensuring that
leased-line circuit costs are set to result in the lowest-cost path.
All switched circuits are members of the same IP network or subnet-
work. Each leased line is a separate network or subnetwork.
1xN Backup—Meshed Network (IP Only)
Figure 14 shows another case of 1xN backup. This time the network is a
packet-switching network (frame relay or X.25 point-to point). Unlike the
network in the previous example, this network does not have a central site.
Clients and servers exist at each of the sites. Thus, traffic flows between
each of the sites. The network backup objective is to open a single switched
circuit when one of the router's packet-switching network-access circuits
fails and still to maintain the ability to communicate between all of the sites.
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