ICND1 WAN Technologies & Network Security 5 — Questions and Answers
Question 1: Which of the following correctly describes a difference between PPP and HDLC on Cisco serial links?
- HDLC supports authentication while PPP does not
- PPP is an open standard supporting multivendor interoperability; Cisco HDLC is proprietary (Correct answer)
- PPP only works on synchronous links; HDLC works on both sync and async
- HDLC supports compression and multilink; PPP does not
Correct answer: PPP is an open standard supporting multivendor interoperability; Cisco HDLC is proprietary
PPP is an open, standards-based protocol (RFC 1661) that works between different vendors, while Cisco's HDLC includes a proprietary type field.
Question 2: What is the role of a crypto map in a Cisco IPsec VPN configuration?
- It defines the encryption keys for SSH sessions
- It binds the transform set, peer address, and interesting traffic together and is applied to an interface (Correct answer)
- It generates RSA key pairs for certificate authentication
- It configures IKE Phase 1 ISAKMP policies
Correct answer: It binds the transform set, peer address, and interesting traffic together and is applied to an interface
A crypto map ties together the ACL (interesting traffic), peer IP, and transform set, then is applied to the outbound interface to activate IPsec.
Question 3: Which NAT type creates a one-to-one permanent mapping between a private IP address and a public IP address?
- Dynamic NAT
- PAT (overload)
- Static NAT (Correct answer)
- NAT64
Correct answer: Static NAT
Static NAT creates a fixed, permanent one-to-one translation between a specific private address and a specific public address.
Question 4: An extended ACL numbered 150 is applied inbound on Fa0/0. In what order does the router process ACL entries?
- From most specific to least specific
- Randomly, choosing the best match
- Sequentially from top to bottom, stopping at the first match (Correct answer)
- By protocol type, processing IP rules before TCP rules
Correct answer: Sequentially from top to bottom, stopping at the first match
ACLs are processed top-to-bottom and the router stops at the first matching entry, making entry order critical.
Question 5: Which WAN technology delivers internet access over standard telephone lines using frequencies above the voice band, allowing simultaneous voice and data?
- ISDN BRI
- T1 leased line
- DSL (Correct answer)
- Frame Relay
Correct answer: DSL
DSL (Digital Subscriber Line) uses higher frequencies on existing copper phone lines, enabling concurrent voice and broadband data.
Question 6: What happens to a packet that reaches the end of an ACL without matching any entry?
- It is forwarded with a warning logged
- It is held in a queue for manual review
- It is dropped due to the implicit deny all (Correct answer)
- It is forwarded and a counter is incremented
Correct answer: It is dropped due to the implicit deny all
Every Cisco ACL ends with an implicit 'deny any' that discards all packets that do not match any explicit entry.
Question 7: Which encapsulation type must be configured on both ends of a serial link when connecting Cisco routers to non-Cisco devices?
- Cisco HDLC
- Frame Relay
- PPP (Correct answer)
- SLIP
Correct answer: PPP
PPP is an open standard that interoperates between different vendors, unlike Cisco's proprietary HDLC which only works Cisco-to-Cisco.
ICND1 WAN Technologies & Network Security 5
Which of the following correctly describes a difference between PPP and HDLC on Cisco serial links?