Ccnas Ch4 Slides

2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential Presentation_ID 1

Chapter 4: Implementing Firewall Technologies

CCNA-Security

Presentation_ID 2 2008 Cisco Systems, Inc. All rights reserved.

Chapter 4: Objectives In this chapter you will:

Configure standard and extended IPv4 ACLs using CLI.

Verify the functionality of a configured ACL in relation to the network topology.

Configure standard and extended IPv4 ACLs using CCP.

Configure TCP established and reflexive ACLs.

Configure dynamic ACLs.

Configure time-based ACLs.

Troubleshoot complex ACL implementations.

Use ACLs to mitigate common network attacks.

Configure IPv6 ACLs using CLI.

Configure object groups for use within an access control entry.

Explain how firewalls are used to help secure networks.

Describe the various types of firewalls.

Configure a classic firewall.

Explain design considerations for implementing firewall technologies.

Explain how Zone-Based Policy Firewalls are used to help secure a network.

Explain the operation of a Zone-Based Policy Firewall.

Configure Zone-Based Policy Firewall with CLI.

Configure a Zone-Based Policy Firewall with CCP.


Chapter

4.0 Introduction

4.1 Access Control Lists

4.2 Firewall Technologies

4.3 Zone-Based Policy Firewalls

4.4 Summary


4.1 Access Control Lists


Configuring Standard and Extended IPv4 ACLs with CLI

Introduction to Access Control Lists

Access Control Lists (ACLs) are widely used for mitigating network attacks and controlling network traffic

Parameters used in security-related ACLs involve IPv4, IPv6 addresses, and TCP and UDP port numbers.



Standard and Extended Numbered IP ACLs

Standard Numbered IP ACL



Standard and Extended Numbered IP ACLs Cont.

ACLs numbered199 or 13001999 are standard IPv4 ACLs.

Standard ACLs match packets by examining the source IP address field in the IP header of that packet.

Standard ACLs are used to filter packets based solely on Layer 3 source information.




Extended Numbered IP ACLs

access-list { acl-# } { permit | deny | remark } protocol

source-addr [ source-wildcard ] destination-

addr [destination-wildcard ] [ operator operand ] [port]

[ established ][ log ]




ACLs numbered 100199 or 20002699 are extended ACLs.

Extended ACLs filter IP packets based on:

Source and destination IP addresses

Source and destination TCP and UDP Ports

Protocol Type

Standard and Extended ACLs are:

Applied on an interface using the ip access-group command.

Applied on a VTY port using the access-class command.



Standard and Extended Named IP ACLs Router(config)# ip access list [standard | extended] name_of_ACL

Standard Named IP ACL example:

Extended Named IP ACL example:



Logging ACL Matches

The Log parameter can be used to log matches to ACLs. The following information is included:

Action - Permit or deny

Protocol - TCP, UDP, or ICMP

Source and destination - IPv4 or IPv6 addresses

TCP and UDP - Source and destination port numbers

For ICMP - Message types

Log messages are generated on the first packet match and then at five-minute intervals after that first packet match.



Access Control Entry (ACE) Rules

An ACL is made up of one or more access control entries (ACEs). The caveats below should be considered when working with ACLs.

Implicit deny all - All Cisco ACLs end with an implicit deny all statement.

Standard ACL packet filtering

Standard ACLs are limited to packet filtering based on source addresses only.

Extended ACLs might need to be created to fully implement a security policy.

Order of statements

ACLs have a policy of first match; when a statement is matched, the list is no longer examined.

Ensure that statements at the top of the ACL do not negate any statements found lower.

Place specific ACL statements higher in the ACL and more general statements near the end.



Access Control Entry Rules (Cont.)

Directional filtering

ACLs can be applied to inbound packets (toward the interface) or outbound packets (away from the interface).

Double-check the direction of data that an ACL is filtering.

Special packets

Router-generated packets, such as routing table updates, are not subject to outbound ACL statements on the source router.

If the security policy requires filtering these types of packets, inbound ACLs on adjacent routers or other router filter mechanisms must be used.

Modifying ACLs

New entries are added to an ACL, and are always added to the bottom.

Starting with Cisco IOS 12.3, sequence numbers can be used to edit an ACL.

The ACL is processed top-down based on the sequence numbers of the statements (lowest to highest).



Standard ACL Example

All traffic from subnet 172.16.4.0 must be denied access to another subnet, but all other traffic should be permitted

R1(config)# access-list 1 deny 172.16.4.0 0.0.0.255

R1(config)# access-list 1 permit any

R1(config)# interface FastEthernet 0/0

R1(config-if)# ip access-group 1 out



Extended ACL Example

FTP traffic from one subnet must be denied on another subnet.

R1(config)# access-list 101 deny tcp 172.16.4.0 0.0.0.255 172.16.3.0 0.0.0.255 eq 21

R1(config)# access-list 101 deny tcp 172.16.4.0 0.0.0.255 172.16.3.0 0.0.0.255 eq 20

R1(config)# access-list 101 permit ip any any



Editing Extended ACLs

The existing access list has three entries:

The access list is edited, adding a new ACE and replacing ACE line 20:

The updated access list has four entries:


Topology and Flow for ACLs

How Cisco Routers Handle ACL Matches

The direction of traffic through a networking device is defined by the ingress (inbound) and egress (outbound) interfaces for the traffic.

Inbound traffic refers to traffic as it enters into the router, prior to the routing table being accessed.

Outbound traffic refers to traffic that entered the router and has been processed by the router to determine where to forward that data.

Depending on the type of device and ACL configured, the return traffic can be dynamically tracked.



How Cisco Routers Handle ACL Matches Cont. Inbound ACL Operation Flow



How Cisco Routers Handle ACL Matches Cont.

Outbound ACL Operation Flow



ACL Placement

Standard ACL Placement

Standard ACLs are placed as close to the destination as possible.

Standard ACLs filter packets are based on the source address only.

Placing standard ACLs that are too close to the source can deny valid traffic.

Extended ACL Placement

Extended ACLs are placed on routers as close as possible to the source that is being filtered.

Placing extended ACLs too far from the source is inefficient use of network resources.



ACL Design

ACLs are used to prevent certain types of traffic from entering a network.

ACLs are used to permit more secure types of traffic, such as HTTPS (TCP port 443), to be used for business purposes.

Effective use of ACLs requires a clear understanding of which ports must be blocked versus permitted and proper of extended ACLs

The Nmap program can be used to determine which ports are open on a given device.



Verifying ACL Functionality

show running-config command

show ip access-lists command


Configuring Standard and Extended ACLs with CCP

Configuring ACLs with CCP

To configure ACLs on a routing device using CCP, the router must first be selected from the drop-down list under Select Community Member.

Next on the CCP application menu bar, click Configure to open the task list.

Open the Router drop-down list >ACL to access the ACL configuration options.



CCP Rules

CCP allows an administrator to create access rules that denies certain types of traffic while permitting other types.

CCP provides default rules that an administrator can use.

The CCP Rules (ACLs) Summary window provides a summary of the rules in the router configuration.



Creating a Rule Using CCP an administrator can create and apply standard rules (Standard ACLs) and extended rules (extended ACLs).

On the CCP menu, click Configure > Router > ACL >ACL Editor.

Click Add to display the Add a Rule window.

In the Add a Rule window, enter a name or number in the Name/Number field.

From the Type drop-down list, select Standard Rule.

Click Add. The Add a Standard Rule Entry window appears.



Applying a Rule to an Interface

After the Rule Entry list is complete, the next step is to apply the rule to an interface.

From the Add a Rule window, click Associate. The Associate with an Interface window displays. Only interfaces with a status of up/up appear in the drop-down list.



Delivering a Rule

After the access rule is created, in the Add a Rule window, click OK.


Configuring TCP Established and Reflexive ACLs

First-Generation Approach to Stateful Firewall

The first-generation IOS traffic filtering solution to support the two-way nature of TCP virtual circuits was the TCP established keyword for extended IP ACLs.

Block all traffic coming from the Internet except for the TCP reply traffic associated with established TCP traffic initiated from inside network.

The second generation IOS solution for session filtering was reflexive ACLs.

Filter traffic based on source and destination addresses, and port numbers, and track sessions.

The TCP established option and reflexive ACLs are examples of complex ACLs.



Monitoring TCP Flag Settings

In 1995, the first-generation IOS traffic filtering solution based on the TCP established keyword for extended IP ACLs.

The TCP established keyword blocks all traffic coming from the Internet, except for the TCP reply traffic associated with established TCP traffic initiated from the inside of the network.

The established keyword forces the router to check whether the TCP ACK or RST control flag is set.

If the ACK flag is set, the TCP traffic is allowed in. If not, it is assumed that the traffic is associated with a new connection initiated from the outside.



TCP Established in Action

R1(config)# access-list 100 permit tcp any eq 443 192.168.1.0 0.0.0.255 established

R1(config)# access-list 100 deny ip any any

R1(config)# interface s0/0/0

R1(config-if)# ip access-group 100 in



Reflexive ACLs

In 1996, the second-generation IOS solution for session filtering was Reflexive ACLs.

Unlike the TCP Established feature, which just used ACK and RST bits, reflexive ACLS filter traffic were based on source, destination addresses, and port numbers.

Session filtering uses temporary filters that are removed when a session is over, adding a time limit on a hackers attack opportunity.

Used to allow IP traffic for sessions originating from within the network while denying IP traffic for sessions originating outside the network.



Reflexive ACLs (cont.)

The router examines the outbound traffic and when it sees a new connection, it adds an entry to a temporary ACL to allow replies back in.

These entries are automatically created when a new IP session begins, for example, with an outbound packet, and the entries are automatically removed when the session ends.



Using Reflexive ACLs

Step 1. Create an internal ACL that looks for new outbound sessions and creates temporary reflexive ACEs.

Step 2. Create an external ACL that uses the reflexive ACLs to examine return traffic.

Step 3. Activate the Named ACLs on the appropriate interfaces.



Using Reflexive ACLs Cont.

Create a reflexive ACL that matches internal users surfing the Internet with a web browser and relying on DNS with a 10-second timeout period.

R1(config)# ip access-list extended INTERNAL_ACL

R1(config-ext-nacl)# permit tcp any any eq 80 reflect WEB-ONLY-REFLEXIVE-ACL

R1(config-ext-nacl)# permit udp any any eq 53 reflect DNS-ONLY-REFLEXIVE-ACL timeout 10

R1(config-ext-nacl)# exit

R1(config)# ip access-list extended EXTERNAL_ACL

R1(config-ext-nacl)# evaluate WEB-ONLY-REFLEXIVE-ACL

R1(config-ext-nacl)# evaluate DNS-ONLY-REFLEXIVE-ACL

R1(config-ext-nacl)# deny ip any any

R1(config-ext-nacl)# exit

R1(config)# interface s0/0/0

R1(config-if)# ip access-group INTERNAL_ACL out

R1(config-if)# ip access-group EXTERNAL_ACL in


Configuring Dynamic ACLs

Dynamic ACLs

Dynamic ACLs are available for IP traffic only.

Dynamic ACLs are dependent on Telnet connectivity, authentication (either local or remote), and extended ACLs.

Dynamic ACLs offer these security benefits over standard and static extended ACLs:

Challenge mechanism to authenticate individual users

Simplified management in large internetworks

Reduced router processing for ACLs

Less opportunity for network break-ins by network hackers

Creation of dynamic user access through a firewall, without compromising other configured security restrictions.



Dynamic ACL Operation

An extended ACL is applied to block all traffic through the router, except Telnet. Users who want to traverse the router are blocked by the ACL until they use Telnet to connect to the router and are authenticated.

Users authenticate using Telnet, and then dropped.

However, a single-entry dynamic ACL is added to the extended ACL that exists.

This permits traffic for a particular period; idle and absolute timeouts are possible.



Dynamic ACL Operation Cont.



Configuring a Dynamic ACL



Dynamic ACL Timeouts

Two timeouts are associated with dynamic ACL entries: absolute and idle.

The absolute timer is specified in the dynamic ACL entry.

The idle timeout value is specified in the autocommand command, which enables lock-and-key

authentication on the vty lines.

If timeouts are not specified, the default is to never time out the entry; therefore, it is recommended to configure a timeout.


Configuring Time-Based ACLs

Time-Based ACLs

Time-based ACLs allow for access control based on time.

Timed-based ACLs enable traffic to be restricted based on the time of day, the day of the week, or the day of the month.



Time-Based ACL Scenario

Users are not allowed to access the Internet during business hours, except during lunch and after hours between 5:00 p.m. and 7:00 p.m.

R1(config)# time-range EMPLOYEE-TIME

R1(config-time-range)# periodic weekdays 12:00 to 13:00

R1(config-time-range)# periodic weekdays 17:00 to 19:00

R1(config-time-range)# exit

R1(config)# access-list 100 permit ip 192.168.1.0 0.0.0.255 any time-range EMPLOYEE-TIME

R1(config)# access-list 100 deny ip any any

R1(config)# interface FastEthernet 0/1

R1(config-if)# ip access-group 100 in

R1(config-if)# exit


Troubleshooting Complex ACL Implementations

Verify and Troubleshoot ACLs

Two commands are very useful for troubleshooting ACLs:

show access-lists

debug ip packet (detail)


Troubleshooting Complex ACL Implementations

Debugging ACLs


Mitigating Attacks with ACLs

Mitigating Spoofing and DoS Attacks

ACLs can be used to mitigate many network threats

IP address spoofing, inbound and outbound

DoS TCP SYN attacks

DoS smurf attacks

ACLs can also filter the following traffic

ICMP messages (inbound and outbound)

traceroute



Antispoofing with ACLs

Deny all IP packets containing the following IP addresses in their source field:

Any local host addresses (127.0.0.0/8)

Any reserved private addresses (RFC 1918)

Any addresses in the IP multicast address range (224.0.0.0/4)

R1(config)# access-list 150 deny ip 0.0.0.0 0.255.255.255 any






R1(config)# access-list 150 deny ip host 255.255.255.255 any



Permitting Necessary Traffic Through a Firewall

DNS, SMTP, and FTP are common services that often must be allowed through a firewall.



Mitigating ICMP Abuse

Hackers use ICMP packets for pings sweeps and DoS flood attacks, and use ICMP redirect messages to alter host routing tables.

Both ICMP echo and redirect messages should be blocked inbound by the router.



Mitigating SNMP Exploits

Management protocols, such as SNMP, while useful for remote monitoring and management of networked devices, can be exploited.

Apply interface ACLs to filter SNMP packets from non-authorized systems.


IPv6 ACLs

IPv6 ACLs

IPv6 ACLs are similar to IPv4 ACLs. They allow filtering on source and destination addresses, source and destination ports, and protocol type.

IPv6 ACLs are created using the ipv6 access-list command.

IPv6 ACLs are applied to an interface using the ipv6 traffic-filter access-list-name {in | out}

command.


IPv6 ACLs

Configuring IPv6 ACLs

All IPv6 ACLs contain two implicit permit statements to allow IPv6 neighbor discovery packets to be sent and received.

permit icmp any any nd-na

permit icmp any any nd-ns

Like IPv4 ACLs, all IPv6 ACLs include an implicit deny as the last statement.

deny ipv6 any any

These statements will not display in the configuration output. A best practice is to manually enter all three implicit commands.

Manually entering the implicit deny statement also allows you to log denied packets without affecting neighbor discovery.


Using Object Groups in ACEs

Object Groups

Object groups are used to classify users, devices, or protocols into groups.

These groups can then be used to create access control policies for groups of objects in easy to read statements.

This feature lets the administrator use object groups instead of individual IP addresses, protocols, and ports, which are used in conventional ACLs.

This results in fewer, more manageable Access Control Entries (ACEs).

Both IPv4 and IPv6 ACLs can use object groups.



Network and Service Object Groups

Object groups must have unique names.

Additional objects can be appended to existing object groups.

Objects such as hosts, protocols, or services can be grouped.

Cannot delete an object group or make an object group empty if it is

being used in an ACE.



Configuring Network and Service Object Groups



Creating an Object Group-Based ACL

In this ACL, all IP addresses and networks specified within the eng_network_group are permitted all services specified in the eng_srv_group.

In the example, the protocol argument (tcp, udp, icmp) is not necessary, because the protocol is specified within the services group.


4.2 Firewall Technologies


Securing Networks with Firewalls

Defining Firewalls

A firewall prevents undesirable traffic from entering prescribed areas within a network.

A firewall is a system or group of systems that enforces an access control policy between networks. For example:

A packet filtering router

A switch with two VLANs

Multiple hosts with firewall software

In 1989, AT&T Bell Laboratories developed the first stateful firewall. A stateful firewall is able to determine if a packet belongs to an existing flow of data.



Defining Firewalls Cont.



Benefits and Limitations of Firewalls

Benefits

Exposure of sensitive hosts and applications to untrusted users can be prevented.

The protocol flow can be sanitized, preventing the exploitation of protocol flaws.

Malicious data can be blocked from servers and clients.

Security policy enforcement can be made simple, scalable, and robust.

Limitations

If misconfigured, can have serious consequences, such as single point of failure.

The data from many applications cannot be passed over firewalls securely.

Users might proactively search for ways around the firewall to receive blocked material, exposing the network to potential attack.

Network performance can slow down.

Unauthorized traffic can be tunneled or hidden as legitimate traffic through the firewall.


Types of Firewalls

Firewall Types Packet filtering firewall - Typically is a router with the

capability to filter some packet content, such as Layer 3 and sometimes Layer 4 information.

Stateful firewall - Monitors the state of connections, whether the connection is in an initiation, data transfer, or termination state.

Application gateway firewall (proxy firewall) - A firewall that filters information at Layers 3, 4, 5, and 7 of the OSI reference model. Most of the firewall control and filtering is done in the software.

Network address translation (NAT) firewall - A firewall that expands the number of IP addresses available and hides network addressing design.


Types of Firewalls

Packet Filtering Firewall Packet-filtering firewalls are usually part of a router firewall

and primarily uses ACLs. It examines a packet based on the information in a packet header.

Packet-filtering firewalls use a simple policy table lookup that permits or denies traffic based on specific criteria:

Source IP address

Destination IP address

Protocol

Source port number

Destination port number

Synchronize/start (SYN) packet receipt


Types of Firewalls

Stateful Firewalls Stateful firewalls are the most versatile and the most common

firewall technologies in use.

Stateful filtering tracks each connection traversing all interfaces of the firewall and confirms that they are valid. The firewall examines information in the headers of Layer 3 packets and Layer 4 segments.

Also called stateful packet filters and application-aware packet filters.

Stateful firewalls have two main improvements over packet filters

Maintain a session table (state table) where they track all connections.

Recognize dynamic applications and know which additional connections will be initiated between the endpoints.


Types of Firewalls

Stateful Firewalls Cont. Stateful firewalls inspect every packet, compare the packet against the

state table, and may examine the packet for any special protocol negotiations.

Stateful firewalls operate mainly at the transport (TCP and UDP) layer.


Types of Firewalls

Cisco Firewall Solutions Cisco Systems provides several options for network security professionals to implement a firewall solution.


Classic Firewall

Classic Firewall Classic Firewall, formerly known as context-based access control

(CBAC)

Classic Firewall provides four main functions that include traffic filtering, traffic inspection, intrusion detection, and generation of audits and alerts

Classic Firewall is a dramatic improvement over the TCP established and reflexive ACL firewalls in several ways

Monitors TCP connection setup

Tracks TCP sequence numbers

Monitors UDP session information

Inspects DNS queries and replies

Inspects common ICMP message types

Supports applications that rely on multiple connections

Inspects embedded addresses

Inspects application layer information


Classic Firewall

Classic Firewall Operation


Classic Firewall

Classic Firewall Operation Cont.

With Classic Firewall, the protocols to inspect are specified in an inspection rule.

An inspection rule is applied to an interface in a direction, either in or out, where the inspection applies.


Classic Firewall

Classic Firewall Configuration

To configure Classic Firewall:

Step 1. Select an interface, either internal or external.

Step 2. Configure IP ACLs at the interface.

Step 3. Define inspection rules.

Step 4. Apply an inspection rule to an interface.


Firewalls In Network Design

Demilitarized Zones

Demilitarized Zones (DMZs) define the portions of a network that are trusted and untrusted.



Layered Defense

Factors to consider when building a complete in-depth defense.



Firewalls and the Security Policy

Firewall Best Practices


4.3 Zone-Based Policy Firewalls


Zone-Based Policy Firewall Characteristics

Zone-Based Policy Firewalls

A Zone-Based Policy Firewall configuration model (ZPF or ZBF or ZFW) was introduced in 2006 with Cisco IOS Release 12.4(6)T.

With ZPF, the interfaces are assigned to zones and then an inspection policy is applied to traffic moving between the zones.

The default policy is to block all traffic, unless explicitly allowed (CBACs default was allow all).

It supports previous firewall features, including Stateful Packet Inspection (SPI), application inspection, URL filtering, and DoS mitigation.



Zone-Based Policy Firewalls Cont.

Not dependent on ACLs.

The router security posture is to block unless explicitly allowed.

Policies are easy to read and troubleshoot with C3PL.

One policy affects any given traffic, instead of needing multiple ACLs and inspection actions.



Zone-Based Policy Firewall Design

Determine the Zones - The internetworking infrastructure under consideration must be split into separate zones with various security levels focusing on the separation of the infrastructure into zones.

Establish policies between zones - For each pair of "source-destination" zones (for example, from inside network to Internet), define the sessions that clients in the source zones can request from servers in destination zones.

Design the physical infrastructure - The administrator must design the physical infrastructure, considering security and availability requirements.

Identify subset within zones and merge traffic requirements - For each firewall device in the design, the administrator must identify zone subsets connected to its interfaces and merge the traffic requirements for those zones.


Zone-Based Policy Firewall Operation

Zone-Based Policy Firewall Actions Inspect

Configures Cisco IOS SPI (equivalent to the ip inspect command).

It automatically allows for return traffic and potential ICMP messages.

For protocols requiring multiple parallel signaling and data sessions (for example, FTP or H.323), the inspect action also handles the proper establishment of data sessions.

Pass

Analogous to a permit statement in an ACL.

It does not track the state of connections or sessions within the traffic.

Pass allows the traffic only in one direction.

A corresponding policy must be applied to allow return traffic to pass in the opposite direction.

Drop

Analogous to a deny statement in an ACL.

A log option is available to log the rejected packets.



Zone-Based Policy Firewall Rules

Rules for Application Traffic



Zone-Based Policy Firewall Rules for Routers

The ZBF rules for a zone-based policy firewall are different when the router is the source or the destination of the traffic.

When an interface is configured to be a zone member, the hosts that are connected to the interface are included in the zone.

However, traffic to the router is not subject to the zone policies.

By default, all router IP interfaces are part of the self zone.

A zone-pair that includes the self zone and associated policy, applies to router generated or traffic destined to the router. It does not apply to traffic traversing the router.

A policy can be defined using the self zone as either the source or the destination zone.

The self zone is a system-defined zone.

It does not require any interfaces to be configured as members.



Zone-Based Policy Firewall Rules for Routers Cont.

The rules depend on whether the router is the source or the destination of the traffic.


Configuring a Zone-Based Policy Firewall with CLI

Configuring Zone-Based Policy Firewalls with CLI

Create the zones for the firewall. zone security

Define traffic classes. class-map type inspect

Specify firewall policies.

policy-map type inspect

Apply firewall policies to pairs of source destination zones. zone-pair

Assign router interfaces to zones. zone-member security



Creating Zones



Defining Traffic Classes



Specifying Firewall Policies



Applying Firewall Policies and Assigning Router Interfaces

The firewall policy is applied to traffic between a pair of zones using the zone-pair security command.

To apply a policy, a zone pair must first be created.

Specify the source zone, the destination zone, and the policy for handling the traffic between them.

Finally the administrator must assign interfaces to the appropriate security zones using the zone-member interface command.


Configuring a Zone-Based Policy Firewall with CCP Wizard

Basic and Advanced Firewall Wizards

The CCP Basic Firewall wizard helps implement a firewall with two zones: an in-zone and an out-zone.

The Advanced Firewall wizard can be used to define a security DMZ used for Internet accessible services, and allows the user to select the level of default security that is initially implemented.



Advanced Firewall Interface Configuration

The first task to enable an advanced firewall configuration is to define inside and outside interfaces.



Security Level Configuration

After performing the interface configuration, the Advanced Firewall Security Configuration window appears.



Deliver Configuration



Manual Configuration with CCP

There are four steps to configure ZPF with CCP:

Step 1. Define zones in the Zone page.

Step 2. Configure class maps to describe traffic between zones.

Step 3. Create policy maps to apply actions to the traffic of the class maps.

Step 4. Define zone pairs and assign policy maps to the zone pairs.



Defining Zones

A zone, or security zone, is a named group of interfaces to which a security policy can be applied.

A zone can contain a single interface or multiple interfaces; however, an interface cannot be a member of more than one zone.



Configuring Class Maps

Class maps identify traffic and traffic parameters for the policy application.



Creating Policy Maps



Defining Zone Pairs



Editing Firewall Policy View



View Firewall Activity



Viewing the Zone-Based Policy Firewall State Table

Use the show policy-map type inspect zone-pair session command to examine the active connections in the ZPF state

table.


4.4 Summary


Chapter 4

Summary Firewalls separate protected areas from non-protected

areas to prevent unauthorized users from accessing protected network resources.

Common methods for implementing firewalls include:

Packet filtering firewall

Stateful firewall

Standard and extended IP ACLs are fundamental tools for basic network traffic filtering and to mitigate a wide range of network attacks.

ACLs can also be configured to temporarily open a hole in a firewall (i.e., dynamic ACL). Additionally, time-based ALCs allow administrators to select the time of day and the days of the week for ACLs to be applied.


Chapter 4

Summary (cont.)

Stateful firewalls can be implemented as follows:

Traffic filtering solutions - Includes ACLs using the TCP established option and reflexive ACLs

Context-based access control (CBAC) ACLs - CABCs enable sophisticated stateful filtering of most forms of modern application traffic.

Zone-Based Policy Firewall - Introduced in 2006, is the state of the art in modern firewalling. The Zone-Based Policy Firewall operation centers around the creation of zones associated with various security levels.

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