Adtran 4120 Manuel D’Utilisation

Chapter 1.  Understanding ISDN and the Express 4110/4120

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Express 4110/4120 User Manual

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The Express 4110/4120 operates as a dial-up IP router when the Configu-
ration/IP/IP Router/Mode

 option is configured to On.  The Express 4110/

4120 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 4110/4120 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.