CCIE Security Written Exam

Here you have the best Cisco 400-251 practice exam questions

You have 686 total questions to study from
Each page has 5 questions, making a total of 138 pages
You can navigate through the pages using the buttons at the bottom
This questions were last updated on October 14, 2025
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Question 1 of 686

A router has four interfaces addressed as 10.1.1.1/24, 10.1.2.1/24, 10.1.3.1/24, and 10.1.4.1/24. What is the smallest summary route that can be advertised covering these four subnets?

10.1.2.0/22

10.1.0.0/22

10.1.0.0/21

10.1.0.0/16

Correct Answer: C

Question 2 of 686

Which protocol does 802.1X use between the supplicant and the authenticator to authenticate users who wish to access the network?

SNMP

TACACS+

RADIUS

EAP over LAN

PPPoE

Correct Answer: D

Question 3 of 686

Which two statements are correct regarding the AES encryption algorithm? (Choose two.)

It is a FIPS-approved symmetric block cipher.

It supports a block size of 128, 192, or 256 bits.

It supports a variable length block size from 16 to 448 bits.

It supports a cipher key size of 128, 192, or 256 bits.

The AES encryption algorithm is based on the presumed difficulty of factoring large integers.

Correct Answer: A, D

Question 4 of 686

What are two benefits of using IKEv2 instead of IKEv1 when deploying remote-access IPsec VPNs? (Choose two.)

IKEv2 supports EAP authentication methods as part of the protocol.

IKEv2 inherently supports NAT traversal.

IKEv2 messages use random message IDs.

The IKEv2 SA plus the IPsec SA can be established in six messages instead of nine messages.

All IKEv2 messages are encryption-protected.

Correct Answer: A, B

Question 5 of 686

DNSSEC was designed to overcome which security limitation of DNS?

DNS man-in-the-middle attacks

DNS flood attacks

DNS fragmentation attacks

DNS hash attacks

DNS replay attacks

DNS violation attacks

Correct Answer: A