ICND1 WAN Technologies & Network Security 3 — Questions and Answers
Question 1: A router is configured with 'ip nat inside source list 1 interface Serial0/0 overload'. What does the 'overload' keyword enable?
- Static NAT for a single host
- PAT (Port Address Translation) using one public IP (Correct answer)
- Dynamic NAT with a pool of addresses
- NAT failover to a backup interface
Correct answer: PAT (Port Address Translation) using one public IP
The 'overload' keyword enables PAT, which multiplexes many private addresses to a single public IP using unique port numbers.
Question 2: Which WAN connection type provides a dedicated, always-on circuit between two locations with guaranteed bandwidth?
- Circuit-switched ISDN
- Packet-switched Frame Relay
- Leased line (point-to-point) (Correct answer)
- DSL broadband
Correct answer: Leased line (point-to-point)
Leased lines provide a permanent dedicated circuit between two sites with consistent, guaranteed bandwidth.
Question 3: What is the function of the 'established' keyword in an extended ACL?
- Permits only ICMP echo replies
- Permits TCP packets that are part of an existing session (ACK or RST set) (Correct answer)
- Blocks new TCP connections while allowing UDP
- Enables stateful inspection on the router
Correct answer: Permits TCP packets that are part of an existing session (ACK or RST set)
The 'established' keyword matches TCP packets with ACK or RST flags set, indicating they belong to an existing connection.
Question 4: In a GRE tunnel configuration, which command defines the tunnel source on a Cisco router?
- tunnel mode gre ip
- tunnel source <interface or IP> (Correct answer)
- tunnel destination <IP>
- ip tunnel source <interface>
Correct answer: tunnel source <interface or IP>
'tunnel source' specifies the interface or IP address used as the GRE tunnel's originating endpoint.
Question 5: Which of the following is a characteristic of CHAP authentication used with PPP?
- Passwords are sent in plaintext
- Authentication occurs only at initial link establishment
- A three-way handshake uses a challenge and MD5 hash (Correct answer)
- It requires a RADIUS server
Correct answer: A three-way handshake uses a challenge and MD5 hash
CHAP uses a three-way handshake where the authenticator sends a challenge and the peer responds with an MD5 hash of the challenge and password.
Question 6: Which protocol is used by MPLS to distribute label information between routers?
- OSPF
- BGP
- LDP (Label Distribution Protocol) (Correct answer)
- RIP
Correct answer: LDP (Label Distribution Protocol)
LDP (Label Distribution Protocol) is the primary protocol used in MPLS networks to exchange label bindings between routers.
Question 7: A standard ACL should be placed as close to which device as possible?
- The source of the traffic
- The destination of the traffic (Correct answer)
- The core switch
- The internet gateway
Correct answer: The destination of the traffic
Standard ACLs filter only by source address, so they must be placed close to the destination to avoid blocking unintended traffic.
ICND1 WAN Technologies & Network Security 3
A router is configured with 'ip nat inside source list 1 interface Serial0/0 overload'.
What does the 'overload' keyword enable?