ADTRAN Express 4100, User Manual

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Chapter 1. Understanding ISDN and the Express 4100/4110
1-8 Express 4100/4110 User Manual 61200176L2-1
IP Routing
The Express 4100/4110 operates as a dial-up IP router when the Configu-
ration/IP/IP Router/Mode
option is configured to On. The Express 4100/
4110 uses an IP unnumbered WAN interface; the IP address and mask
assigned to the unit’s LAN interface apply to all routing and IP operations
for the unit. If a default gateway is specified on the network of the Ether-
net interface, the unit attempts to reach the gateway through that inter-
face. If the gateway is specified on an unknown network, the unknown
network is assigned to the router table and remains unused until that
gateway becomes the peer on a WAN connection. If no default gateway is
specified, the first connected peer on the WAN interface becomes the
default gateway (recommended for remote applications when there are
no other routers on the remote LAN).
For each profile in the Connection List that includes an IP address and has
the Configuration/Connection List/IP/Route/Static Route option set to
Yes
, the Network Address of the specified IP address is added to the
router table with the Host Address as the gateway. If the Configuration/
Connection List/IP/Route/Private
option is set to No, the route is adver-
tised at the specified metric through the unit’s interfaces as if a connection
is active to that network. These routes are referred to as spoofed routes.
Attempts by any computer connected to the LAN interface to access a
host on a spoofed network causes a connection to be attempted using the
information from that Connection List profile. Once connected, routes
advertised by the peer router are learned and advertised to the local LAN.
If Bandwidth-On-Demand is enabled and an Idle Time-out value is speci-
fied, expiration of the Idle Timer causes the link to be disconnected; the
routes learned from the peer router are retained if the Configuration/
Connection List/IP/RIP/Retain
option is set to Yes and advertised as if
the connection is still active. These routes are referred to as retained routes.
Attempts by any connected computer to access a host on any of the
retained routes causes the link to be redialed. If Hang Up is activated
from the Dial menu when the link is down, the retained routes are
removed.
The Express 4100/4110 can be connected to two WAN destinations at the
same time. Each B-channel is dialed to a different location. Routes learned
from one WAN destination are advertised to the other using RIP.