Module 4: ACL Concepts Flashcards
What do routers make routing decisions based on?
Information in the packet header
How is traffic routed when entering a router interface?
Solely based on information within the routing table
What does the router compare to find the best match for routing?
The destination IP address with routes in the routing table
What is the purpose of an access control list (ACL)?
To filter packets based on information found in the packet header
By default, do routers have any ACLs configured?
No
What happens when an ACL is applied to a router interface?
The router evaluates all network packets as they pass through the interface
What is the role of access control entries (ACEs) in an ACL?
A sequential list of permit or deny statements
Fill in the blank: An ACL is a series of _______ commands used to filter packets.
lOS
True or False: A router forwards packets based on the best match route found in the routing table.
True
What are ACEs commonly referred to as?
ACEs are also commonly called ACL statements.
ACL stands for Access Control List.
What happens when network traffic passes through an interface configured with an ACL?
The router compares the information within the packet against each ACE, in sequential order.
This is essential for determining if the packet matches one of the ACEs.
What is the process called when a router checks packets against ACEs?
Packet filtering.
Packet filtering is crucial for managing network traffic and security.
What do several tasks performed by routers require?
The use of ACLs to identify traffic.
ACLs help in controlling the flow of traffic based on defined rules.
What is the purpose of limiting in unnecessary network traffic?
To increase network performance
Reducing unnecessary traffic allows for better bandwidth management and improved application responsiveness.
What type of high bandwidth traffic is often prohibited by a corporate policy to reduce network load?
Video traffic
Video traffic can consume significant bandwidth, impacting overall network performance.
How can a policy to block video traffic be enforced?
Using ACLs (Access Control Lists)
ACLs can specify which types of traffic are allowed or denied on a network.
What is traffic flow control?
A corporate policy that requires routing protocol traffic to be limited to certain links only.
Traffic flow control helps manage network efficiency and security.
How can a corporate policy be implemented to control routing protocol traffic?
Using ACLs to restrict the delivery of routing updates to only those that come from a known source.
ACLs (Access Control Lists) are used to enhance network security by defining permissions for traffic.
What is the basic level of security for network access?
Restricted access to authorized users only
This ensures that only individuals with permission can access sensitive information.
What does corporate policy demand regarding access to confidential networks?
Access must be restricted to authorized users only
This policy is crucial for protecting sensitive employee information.
How can a policy be enforced to limit access to specified networks?
Using Access Control Lists (ACLs)
ACLs are used to define which users or systems are granted or denied access to specific resources.
What does corporate policy require regarding network traffic?
Certain traffic, such as email, must be permitted while other traffic, like Telnet access, must be denied.
This reflects the need to control access and protect network integrity.
How can a policy be implemented to filter traffic by type?
Using ACLs (Access Control Lists) to filter traffic.
ACLs are a set of rules that determine what traffic is allowed or denied on a network.
True or False: All traffic types should be allowed into a network in order to not impact usability.
False
Some traffic must be denied, such as Telnet access because it’s not secure.
Fill in the blank: A policy can be implemented using _______ to filter traffic by type.
ACLs
ACLs help in managing network security by controlling traffic flow.
What is the purpose of a screen host?
To permit or deny access to network services
Screen hosts act as a gatekeeper for network access.
What must be considered when it comes to permitting or denying access to certain file types?
Access to some file types (e.g., FTP or HTTP) must be limited to user groups yet available to others.
This ensures that only authorised users can access sensitive or specific file types.
How can a policy be implemented to control user access to services?
Using ACLs (Access Control Lists) to filter user access
ACLs are a common method for defining who can access what resources in a network.
Fill in the blank: Corporate policy often requires that access to some file types be limited to _______.
Authorised user groups
This is aimed at protecting sensitive information from unauthorised access.
What is the purpose of providing priority to certain classes of network traffic?
To ensure that critical traffic, like voice traffic, is forwarded as fast as possible to avoid interruptions.
How can a policy be implemented to prioritize voice traffic?
Using ACLs and QoS services
What is packet filtering?
Packet filtering controls access to a network by analyzing incoming and/or outgoing packets and forwarding or discarding them based on given criteria.
At which OSI layers does packet filtering occur?
Packet filtering can occur at Layer 3 and Layer 4.
Fill in the blank: Packet filtering controls access to a network by analyzing the incoming and/or outgoing packets and ______ them based on given criteria.
[forwarding or discarding]
What do standard ACLs filter?
Standard ACLs filter at Layer 3 using the source IPv4 address only.
Standard ACLs provide basic filtering capabilities.
What additional features do extended ACLs provide compared to standard ACLs?
Extended ACLs filter at Layer 3 using the source and/or destination IPv4 address and can also filter at Layer 4 using TCP, UDP ports, and optional protocol type information.
Extended ACLs allow for more granular control over network traffic.
What do ACLs define?
The set of rules that give added control for packets that enter inbound interfaces, relay through the router, and exit outbound interfaces of the router.
Can ACLs be configured for both inbound and outbound traffic?
Yes, ACLs can be configured to apply to both inbound traffic and outbound traffic.
Do ACLs act on packets that originate from the router itself?
No, ACLs do not act on packets that originate from the router itself.
What is the purpose of an inbound ACL?
Filters packets before they are routed to the outbound interface
Inbound ACLs are efficient as they save routing lookup overhead if packets are discarded.
How does an inbound ACL handle permitted packets?
Permitted packets are processed for routing
This allows the packet to proceed through the network.
When are inbound ACLs most effectively used?
When the network attached to an inbound interface is the only source of packets that need to be examined
This ensures focused filtering of relevant traffic.
What is the function of an outbound ACL?
Filters packets after they have been routed, regardless of the inbound interface
Outbound ACLs apply rules to traffic exiting the network.
How are incoming packets processed in relation to outbound ACLs?
Incoming packets are routed to the outbound interface and then processed through the outbound ACL
This means outbound ACLs evaluate packets after routing decisions have been made.
When are outbound ACLs best utilized?
When the same filter will be applied to packets from multiple inbound interfaces before exiting the same outbound interface
This allows for centralized filtering of outgoing traffic.
What is the first step when an ACL is applied to an interface?
The router extracts the source IPv4 address from the packet header.
What does the router do after extracting the source IPv4 address?
The router starts at the top of the ACL and compares the source IPv4 address to each ACE in a sequential order.
What happens when a match is made between the source IPv4 address and an ACE?
The router carries out the instruction, either permitting or denying the packet, and the remaining ACEs in the ACL are not analyzed.
What occurs if the source IPv4 address does not match any ACEs in the ACL?
The packet is discarded due to an implicit deny ACE automatically applied to all ACLs.
What does ACE stand for in the context of ACL?
Access Control Entry