Configuring ACL for TCP ACK Packets

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Questions and Answers

What is the purpose of the ACL being configured by the engineer?

To deny all TCP packets
To block packets with an ACK in the TCP header
To permit packets with an ACK in the TCP header (correct)
To accept all IP packets regardless of ACK

What is the significance of 'established' in an ACL entry?

It matches packets that are part of an existing connection (correct)
It matches packets with a specific IP address
It matches packets with an ACK in the TCP header
It matches packets with a specific TCP port

What is the purpose of 'tcp-ack' in an ACL entry?

To match packets with a specific IP address
To match packets with a specific sequence number
To match packets with an ACK in the TCP header (correct)
To match packets with a specific TCP port

What is the correct syntax to permit TCP packets with an ACK in the header?

access-list 10 permit tcp any any ack (D) Signup and view all the answers

What is the significance of the number '21' in an ACL entry?

It specifies the TCP port number (A) Signup and view all the answers

What does the 'established' keyword in an ACL entry indicate?

The packet is part of an existing connection (D) Signup and view all the answers

What is the purpose of the 'eq 21' parameter in the ACL entry?

To specify the FTP control port (D) Signup and view all the answers

Why is the 'tcp-ack' keyword not necessary in the ACL entry?

Because 'established' implies the presence of an ACK (D) Signup and view all the answers

What is the effect of including the 'any any' parameters in the ACL entry?

It allows packets from any source to any destination (D) Signup and view all the answers

What is the purpose of the ACL entry access-list 10 permit tcp any any eq 21 established?

To permit TCP packets with an ACK flag to FTP control port (C) Signup and view all the answers

Study Notes

Configuring ACL for TCP ACK Packets

To allow packets with ACK in the TCP header, an ACL entry is required
The correct ACL entry includes the "established" keyword, indicating that the packet has the ACK flag set
The correct answer is B. access-list 10 permit tcp any any eq 21 established
The "established" keyword is used to match packets that are part of an established connection, which includes ACK packets
Option B is the correct answer because it includes the "established" keyword, which ensures that only packets with the ACK flag set are permitted

Configuring ACLs for TCP Packets

To permit packets with an ACK in the TCP header, an ACL entry is required.
The correct ACL entry is: access-list 10 permit tcp any any eq 21 established
This entry allows TCP packets on port 21 that have the ACK flag set, indicating acknowledgement of received data.
The established keyword is crucial, as it ensures only packets belonging to an established connection are permitted.

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Description

This quiz tests your knowledge of configuring Access Control Lists (ACLs) to permit packets with specific TCP header flags. Learn how to create an ACL that allows packets with ACK flags.