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Practical Exercise 3-2: Connecting Routers Back-to-Back Through the AUX Ports

This sample configuration shows you how to directly connect two routers without using a modem or other DCE devices. In this configuration, two Cisco routers are connected back-to-back through the asynchronous AUX ports using a null modem cable (rollover cable). The AUX ports of the two routers are directly connected using a rollover cable with Point-to-Point Protocol (PPP) running on the link. The AUX ports are DTE devices. Connecting DTE to DTE devices requires a null modem cable (rollover cable).

A flat-satin rollover (null modem) cable (part number CAB-500RJ=) is usually provided with every Cisco router to allow for RJ-45 console connectivity. If the AUX port is a DB-25, use an RJ-45-to-DB-25 adapter marked "terminal" with the null modem cable (rollover cable).

This exercise uses the network setup shown in Figure 3-6.

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