Patton electronic 1082/I

Figure 2.

Cisco router with serial interface, conﬁgured as PPP Half-Bridge

Figure 2 shows a typical Cisco router with a serial interface conﬁgured

as a PPP Half Bridge. The router serial interface uses a remote device

that supports PPP bridging to function as a node on the remote Ethernet

network. The serial interface on the Cisco will have an IP address on the

same Ethernet subnet as the bridge.

For example, the customer site is assigned the addresses 192.168.1.0/

24 through 192.168.1.1/24. The address 192.168.1.1/24 is also the

default gateway for the remote network. The above settings remove any

routing/forwarding intelligence from the CPE. The associated Cisco con-

ﬁguration will set serial interface (s0) to accommodate half bridging for

the above example.

Authentication is optional under PPP. In a point-to-point leased-line link,

incoming customer facilities are usually ﬁxed in nature, therefore authen-

tication is generally not required. If the foreign device requires authenti-

cation via PAP or CHAP, the PPP software will respond with default Peer-

ID consisting of the units Ethernet MAC address and a password which

consists of the unit’s Ethernet MAC address.

Some networking systems do not deﬁne network numbers in packets

sent out over a network. If a packet does not have a speciﬁc destination

network number, a router will assume that the packet is set up for the

local segment and will not forward it to any other sub-network. However,

in cases where two devices need to communicate over the wide-area,

bridging can be used to transport non-routable protocols.

Patton

1082/I

Bridge

Ethernet LAN

PEC device with

serial interface

Patton 1082/C

connected to a router