- (Exam Topic 4)
Why would a customer implement an on-premises solution instead of a cloud solution?
Correct Answer:
D
- (Exam Topic 3)
An engineer must configure an ACL that permits packets which include an ACK in the TCP header Which entry must be included in the ACL?
Correct Answer:
D
The established keyword is only applicable to TCP access list entries to match TCP segments that have the ACK and/or RST control bit set (regardless of the source and destination ports), which assumes that a TCP connection has already been established in one direction only. Let’s see an example below:
Suppose you only want to allow the hosts inside your company to telnet to an outside server but not vice versa, you can simply use an ”established” access-list like this:
access-list 100 permit tcp any any established access-list 101 permit tcp any any eq telnet
!
interface S0/0
ip access-group 100 in ip access-group 101 out
Note: Suppose host A wants to start communicating with host B using TCP. Before they can send real data, a three-way handshake must be established first. Let‘s see how this process takes place:
* 1. First host A will send a SYN message
(a TCP segment with SYN flag set to 1, SYN is short for
SYNchronize) to indicate it wants to setup a connection with host B. This message includes a sequence (SEQ) number for tracking purpose. This sequence number can be any 32-bit number (range from 0 to 232) so we use ”x” to represent it.
* 2. After receiving SYN message from host A, host B replies with SYN-ACK message (some books may call it SYN/ACK or SYN, ACK message. ACK is short for ACKnowledge). This message includes a SYN sequence
number and an ACK number:
+ SYN sequence number (let‘s called it “y”) is a random number and does not have any relationship with Host A‘s SYN SEQ number.
+ ACK number is the next number of Host A‘s SYN sequence number it received, so we represent it with “x+1. It means I received your part. Now send me the next part (x + 1)”.
The SYN-ACK message indicates host B accepts to talk to host A (via ACK part). And ask if host A still wants to talk to it as well (via SYN part).
* 3. After Host A received the SYN-ACK message from host B, it sends an ACK message
“y+1” to host B. This confirms host A still wants to talk to host B.
- (Exam Topic 2)
Refer to the exhibit.
A network architect has partially configured static NAT. which commands should be asked to complete the configuration?
Correct Answer:
B
- (Exam Topic 4)
Refer to the exhibit. R1 and R2 are directly connected, but the BGP session does not establish. Which action must be taken to build an eBGP session?
Correct Answer:
D
- (Exam Topic 2)
Refer to the exhibit.
Which JSON syntax is derived from this data?
A)
B)
C)
D)
Correct Answer:
D