200-101 · Question #49
200-101 Question #49: Real Exam Question with Answer & Explanation
The correct answer is B: Main(config)# interface serial 0/0 Main(config)# ip address 172.16.1.1 255.255.255.252 Main(config)# encapsulation PPP Main(config)# no shut. When connecting a Cisco router to a non-Cisco router over a serial link, you must use PPP encapsulation instead of the default Cisco HDLC. This is because Cisco's HDLC implementation includes a proprietary field that non-Cisco devices do not understand, making it incompatible. PP
Question
Options
- AMain(config)# interface serial 0/0 Main(config)# ip address 172.16.1.1 255.255.255.252 Main(config)# no shut
- BMain(config)# interface serial 0/0 Main(config)# ip address 172.16.1.1 255.255.255.252 Main(config)# encapsulation PPP Main(config)# no shut
- CMain(config)# interface serial 0/0 Main(config)# ip address 172.16.1.1 255.255.255.252 Main(config)# encapsulation frame-relay Main(config)# authentication chap Main(config)# no shut
- DMain(config)# interface serial 0/0 Main(config)# ip address 172.16.1.1 255.255.255.252 Main(config)# encapsulation Ietf Main(config)# no shut
Explanation
When connecting a Cisco router to a non-Cisco router over a serial link, you must use PPP encapsulation instead of the default Cisco HDLC. This is because Cisco's HDLC implementation includes a proprietary field that non-Cisco devices do not understand, making it incompatible. PPP is an open, vendor-neutral standard that any compliant router supports. Option B is correct because it configures the IP address and explicitly sets 'encapsulation PPP', then enables the interface. Option A uses the default Cisco HDLC which would fail with a non-Cisco router. Options C and D are incorrect configurations.
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