ADTRAN Express L1.5, User Manual

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Chapter 1: Understanding HDSL and the Express L768/L1.5
61202192L1-1 Express L768/L1.5 User Manual 9
IP Routing
The Express L768/L1.5 operates as an IP router when the Configuration/IP/IP
Router/Mode option is configured to On . In PPP mode, the Express L768/L1.5
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. In
Frame Relay mode, each PVC can be specified as numbered or unnumbered
links. If a default gateway is specified on the network of the Ethernet interface,
the unit attempts to reach the gateway through that interface. If no default
gateway is specified (i.e., 0.0.0.0) the WAN interface becomes the default gate-
way (recommended for remote applications when there are no other routers
on the remote LAN).
IPX Routing
Network routes and services are learned and advertised using Novell’s RIP
and SAP.
Concurrent Routing And Bridging
The Express L768/L1.5 can route IP and IPX as well as bridge non-IP/IPX
packets simultaneously. The PPP profile will by default negotiate PPP net-
work protocols to support the transmission and reception of IP, IPX, and
Bridge packets. If the PPP peer does not accept a protocol, the Express L768/
L1.5 will fall back to any combination of routing and bridging.
Network Address Translation Mode
NAT is a special mode of operation in which the Express L768/L1.5 obtains a
dynamically assigned IP address from the peer router (typically an Internet
Service Provider). This allows a network of computers to appear as a single IP
address.
NAT is enabled if the layer two protocol is PPP and the PPP profile has the IP
parameter
NAT set to Yes , or the layer two protocol is Frame Relay and a
DLCI mapping has the IP Map/Nat parameter set to Yes . The network com-
puter’s IP stack may use DHCP to request an IP address, default gateway ad-
dress, and domain name server addresses from the Express L768/L1.5.