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There are some issues about which you should be aware when
implementing an IP bridging solution.
■
Although calls to the remote site are only generated when data is
addressed to a specific IP host or hosts (in our example, 191.100.100.100),
any data that cannot be identified as local is also passed over the link
while it is open. This can prevent the link from closing after the intended
data has been transferred.
■
Some devices and applications (for example autodiscovery programs
on SNMP managers) poll all devices on a subnet at regular intervals
and this could lead to frequent ISDN calls if you have entered several IP
hosts to generate autocalls to the remote site. When combined with
the problem described above, you could find your ISDN line
permanently connected.
To avoid this situation you need to be sure that no devices or
applications exist on your local site that could make unnecessary and
costly calls to your remote site. You can also configure the
AccessBuilder units at both ends of the link to implement a Firewall
and/or Call Guillotine to reduce the amount of traffic permitted to pass
across the link. See the
AccessBuilder ISDN Access Router Software
Reference
guide for more information about these features.
Alternatively, you may wish to configure the module to operate as a
router to prevent this problem occurring altogether. This however,
requires that each site consists of separate subnets. See the next
section for more information about IP routing.