Patton electronic Model 2707/I, Model 2707/C, Router, Internet, Ethernet, Customer’s Site

Model 2707/I		Model 2707/C
	E1	Router
		Internet
Ethernet
LAN
Customer’s Site		Service Provider’s Network

Figure 1. Cisco router with serial interface, configured as PPP Half Bridge.

Figure 1 shows a typical Cisco router with a serial interface configured as a PPP Half Bridge. The router serial interface connects to the WAN via a 2707/C (V.35) E1 NTU and to the remote 2707/I with support for

PPPbridging. The 2707/I functions 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 2707/I. The associated Cisco configuration will set serial interface (s0) to accommodate half bridging for the above example.

!

interface s0 ppp bridge ip

ip address 192.168.1.1 255.255.255.0

!

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.

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.

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