Hypertec ISDN 10T Router - Manual (Page 17)

Concepts and Principles of Operation
10
You can set Hypertec Router IP addresses to be 'un-numbered' or ‘numbered’. By setting it to “un-
numbered”, you can route IP over a link between two devices without assigning IP addresses to the
ISDN interfaces. This allows you to save valuable IP address space. There are situations where a
traditional “numbered” IP address scheme is inevitable.
In Figure 0-2, Unnumbered ISDN Link, there is an unnumbered link between an ISDN router and a remote
router at the ISP site. These two devices can still communicate with each other, although neither of the
ISDN interfaces has been assigned an IP address. Instead, a route is assigned between a device and its
destination network, using interfaces instead of IP addresses.
SOHO ISDN Router Remote Router at ISP
unnumbered link
eth1
50.0.0.1 eth1
90.0.0.1
Figure 0-2, Unnumbered ISDN Link
In Figure 0-3, Numbered ISDN Link, there is an numbered link between an ISDN router and a remote
router at the ISP site. An IP address is assigned at each end of the numbered link.
SOHO ISDN Router Remote Router at ISP
numbered link
66.0.0.1 66.0.0.2 eth1
50.0.0.1 eth1
90.0.0.1
Figure 0-3, Numbered ISDN Link
Dynamic IP address Assignment
If you are subscribing to a single user account, the ISP won’t assign you a static (semi-permanent) IP
address(es). Instead, an IP address is dynamically assigned at the login time. Hypertec ISDN 10T
Router will accept the dynamically assigned IP address for its ISDN interface and update the routing
table accordingly. The assigned IP address will be freed, and the associated routing table entry is
deleted when the session is closed. The NAT feature is required for multiple LAN users to access the
Internet using the single IP account.