Cisco ENCOR IP Services and QoS 2 — Questions and Answers
Question 1: What is the purpose of the DHCP Option 82 (Relay Agent Information)?
- Specify the DNS server address
- Insert client location information to help assign IP addresses based on port or VLAN (Correct answer)
- Authenticate DHCP clients
- Enable DHCP failover
Correct answer: Insert client location information to help assign IP addresses based on port or VLAN
DHCP Option 82 allows relay agents to insert circuit ID and remote ID information, enabling the DHCP server to make location-aware assignments.
Question 2: In SNMPv3, which security level provides both authentication and encryption?
- noAuthNoPriv
- authNoPriv
- authPriv (Correct answer)
- readOnly
Correct answer: authPriv
The authPriv security level uses HMAC for authentication and DES/AES for privacy (encryption) of SNMP messages.
Question 3: What is the function of IP SLA in Cisco IOS?
- Shape outbound traffic
- Proactively measure network performance metrics like latency, jitter, and packet loss (Correct answer)
- Assign DSCP markings
- Configure QoS policies
Correct answer: Proactively measure network performance metrics like latency, jitter, and packet loss
Cisco IP SLA generates synthetic test traffic to continuously measure network performance metrics such as delay, jitter, and availability.
Question 4: Which QoS mechanism discards excess traffic above a defined rate without buffering it?
- Shaping
- Policing (Correct answer)
- WRED
- Scheduling
Correct answer: Policing
Traffic policing drops or re-marks packets that exceed the configured rate, unlike shaping which buffers excess traffic.
Question 5: What is the default behavior of NTP authentication when configured with 'ntp authenticate' but no trusted keys?
- All NTP peers are trusted
- NTP synchronization is blocked because no keys are trusted (Correct answer)
- Authentication is disabled
- Only Stratum 1 servers are trusted
Correct answer: NTP synchronization is blocked because no keys are trusted
Enabling NTP authentication without defining trusted keys prevents synchronization because no valid key exists to authenticate any source.
Question 6: Which mechanism does WRED use to proactively drop packets before a queue fills completely?
- Tail drop at 100% queue depth
- Random early detection based on average queue depth and DSCP/IP Precedence (Correct answer)
- Priority inversion
- Strict scheduling
Correct answer: Random early detection based on average queue depth and DSCP/IP Precedence
WRED randomly drops packets based on average queue depth and traffic priority before the queue fills, reducing TCP synchronization.
Cisco ENCOR IP Services and QoS 2
What is the purpose of the DHCP Option 82 (Relay Agent Information)?