Operation Manual

36 NetWare MultiProtocol Router for ISDN 3.1 Installation and ISDN Configuration Guide
- When setting up dial-around scenarios, all ISDN-specific configu-
rations and parameters to handle a connection will not only be
negotiated once for each destination and then be active over
months or years, but will be negotiated as often as a logical ISDN
connection set-up to each destination is initiated by any method
and will be released as soon as the logical ISDN connection is
cleared down by any method.
Be More Careful When Using ISDN Interfaces Dynamically
When using ISDN interfaces dynamically, you have to be more
careful when designing your networks and configuring the ISDN
specifics and take a closer look at all configuration interdependen-
cies arising from network and ISDN behavior.
♦♦ Networking processes corrupted
First, you must take care that no networking process is corrupted
because a physical link to a remote site is required for this process to
work, but is not available at that time since the ISDN interface and
the underlying B channel is already set up to another destination.
♦♦ Frequent call set-up due to packets not filtered or spoofed
on the network level
Second, and especially when using static routes/services instead of
any kind of "controlled" connection set-up (CALLMGR or CICC),
any packet addressed to a remote site results in a network request
processed to the ISDN interface. If the ISDN interface is available at
that time, i.e. not yet logically connected to any destination, it does
not know about any of the configured ISDN-related connection
specifics for the destination it is requested to set up the call to, since
all ISDN-specific parameters such as filters and spoofings are not
active to any remote site until the logical ISDN connection has been
negotiated and set up but do only apply afterwards until this logical
ISDN connection is cleared down again. Thus, for any packets you
do not want to have an ISDN line to be set up for, you must set the
appropriate filter already on the network level by using FILTCFG.
With static routes/services, further make sure that you only
configured those remote servers/services on your router that are
required for the networking processes that shall run over ISDN with
the remote site. This is an additional important method you can
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