ccnas chap 2

8/4/2019 Ccnas Chap 2

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Network Security System

Khaled KESSALI

Chapter TwoSecuring Network Devices
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Lesson Planning

This lesson should take 3-6 hours to present The lesson should include lecture,

demonstrations, discussion and assessment The lesson can be taught in person or using

remote instruction


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Major Concepts

Discuss the aspects of router hardening Configure secure administrative access and

router resiliency Configure network devices for monitoring

administrative access

Demonstrate network monitoring techniques Secure IOS-based Routers using automated

features


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Lesson Objectives

Upon completion of this lesson, the successful participant will beable to:1.Describe how to configure a secure network perimeter2.Demonstrate the configuration of secure router administration access3.Describe how to enhance the security for virtual logins4.Describe the steps to configure an SSH daemon for secure remotemanagement5.Describe the purpose and configuration of administrative privilege levels6.Configure the role-based CLI access feature to provide hierarchicaladministrative access


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Lesson Objectives7. Use the Cisco IOS resilient configuration feature to secure the Cisco IOS

image and configuration files8. Describe the factors to consider when securing the data that transmits

over the network related to the network management and reporting of device activity

9. Configure syslog for network security10. Configure SNMP for network security11. Configure NTP to enable accurate time stamping between all devices12. Describe the router services, interfaces, and management services that

are vulnerable to network attacks and perform a security audit13. Lock down a router using AutoSecure14. Lock down a router using SDM


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Perimeter Implementations Single Router Approach

A single router connects theinternal LAN to the Internet. Allsecurity policies are configuredon this device.

Defense-in-depth ApproachPasses everything through to thefirewall. A set of rulesdetermines what traffic therouter will allow or deny.

DMZ ApproachThe DMZ is set up between tworouters. Most traffic filtering leftto the firewall

LAN 1192.168.2.0

Router 1 (R1)

Internet

LAN 1192.168.2.0

R1Internet

Firewall

LAN 1192.168.2.0

R1Internet

R2Firewall

DMZ


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Areas of Router Security Physical Security

Place router in a secured, locked room Install an uninterruptible power supply

Operating System Security Use the latest stable version that meets network requirements Keep a copy of the O/S and configuration file as a backup

Router Hardening Secure administrative control Disable unused ports and interfaces Disable unnecessary services


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Banner Messages Banners are disabled by default and must be explicitly

enabled.

There are four valid tokens for use within the message sectionof the banner command: $(hostname) Displays the hostname for the router $(domain) Displays the domain name for the router $(line) Displays the vty or tty (asynchronous) line number $(line-desc) Displays the description that is attached to the line

R1(config)# banner { exec | incoming | login | motd | slip-ppp }d message d


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SSH version 1, 2

Configuring Router SSH Commands

Connecting to Router Using SDM to configure the SSH Daemon

What's the difference between versions 1 and 2 of

the SSH protocol?
http://www.snailbook.com/faq/ssh-1-vs-2.auto.htmlhttp://www.snailbook.com/faq/ssh-1-vs-2.auto.htmlhttp://www.snailbook.com/faq/ssh-1-vs-2.auto.htmlhttp://www.snailbook.com/faq/ssh-1-vs-2.auto.html


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Preliminary Steps for Configuring SSL

Complete the following prior to configuring routers for the SSHprotocol:

1. Ensure that the target routers are running a Cisco IOS Release12.1(1)T image or later to support SSH.

2. Ensure that each of the target routers has a unique hostname. 3. Ensure that each of the target routers is using the correct domain

name of the network. 4. Ensure that the target routers are configured for local authentication,

or for authentication, authorization, and accounting (AAA) servicesfor username or password authentication, or both. This is mandatoryfor a router-to-router SSH connection.


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Configuring the Router for SSHR1# conf tR1(config)# ip domain-name span.comR1(config)# crypto key generate rsa general-keysmodulus 1024The name for the keys will be: R1.span.com

% The key modulus size is 1024 bits% Generating 1024 bit RSA keys, keys will be non-exportable...[OK]

R1(config)#*Dec 13 16:19:12.079: %SSH-5-ENABLED: SSH 1.99 hasbeen enabledR1(config)# username Bob secret ciscoR1(config)# line vty 0 4R1(config-line)# login localR1(config-line)# transport input sshR1(config-line)# exit

1. Configure the IP domainname of the network

2. Generate one waysecret key

3. Verify or create a localdatabase entry

4. Enable VTY inboundSSH sessions


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Optional SSH CommandsR1# show ip sshSSH Enabled - version 1.99Authentication timeout: 120 secs; Authenticationretries: 3R1#R1# conf tEnter configuration commands, one per line. Endwith CNTL/Z.R1(config)# ip ssh version 2R1(config)# ip ssh time-out 60R1(config)# ip ssh authentication-retries 2R1(config)# ^ZR1#R1# show ip sshSSH Enabled - version 2.0Authentication timeout: 60 secs; Authenticationretries: 2R1#


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Connecting to the RouterThere are two different ways toconnect to an SSH-enabled router:

Connect using an SSH-enabled Ciscorouter

Connect using an SSH client running on ahost.

R1# sho sshConnection Version Mode Encryption Hmac State Username0 2.0 IN aes128-cbc hmac-sha1 Session started Bob0 2.0 OUT aes128-cbc hmac-sha1 Session started Bob%No SSHv1 server connections running.R1#

R1# sho ssh%No SSHv2 server connections running.%No SSHv1 server connections running.R1#

R2# ssh -l Bob 192.168.2.101

Password:

R1>

1

2

3

There are no current SSH sessions ongoing with R1.

R2 establishes an SSH connection with R1.

There is an incoming and outgoing SSHv2 session user Bob.


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Using SDM1. Choose Configure > Additional Tasks > Router Access > SSH

2. Possible status options:- RSA key is not set on this router- RSA key is set on this router

3. Enter a modulus size andgenerate a key, if there isno key configured

4. To configure SSH on the vty lines,choose Configure > AdditionalTasks > Router Access > VTY


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Config AAA, Show,Firewall, IDS/IPS,NetFlow

Configuring for Privilege Levels

By default: User EXEC mode (privilege level 1) Privileged EXEC mode (privilege level 15)

Sixteen privilege levels available Methods of providing privileged level access infrastructure

access: Privilege Levels Role-Based CLI Access


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Privilege CLI Command

router(config)# privilege mode {level level command | reset command }

Command Description mode Specifies the configuration mode. Use the privilege ?

command to see a complete list of router configurationmodes available

level (Optional) Enables setting a privilege level with aspecified command

level command (Optional) The privilege level associated with acommand (specify up to 16 privilege levels, usingnumbers 0 to 15)

reset (Optional) Resets the privilege level of a commandCommand (Optional) Resets the privilege level


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Privilege Levels for Users

A USER account with normal, Level 1 access. A SUPPORT account with Level 1 and ping command access. A JR-ADMIN account with the same privileges as the SUPPORT accountplus access to the reload command. An ADMIN account which has all of the regular privileged EXEC

commands.

R1# conf tR1(config)# username USER privilege 1 secret ciscoR1(config)#R1(config)# privilege exec level 5 pingR1(config)# enable secret level 5 cisco5R1(config)# username SUPPORT privilege 5 secret cisco5R1(config)#R1(config)# privilege exec level 10 reloadR1(config)# enable secret level 10 cisco10R1(config)# username JR-ADMIN privilege 10 secret cisco10R1(config)#R1(config)# username ADMIN privilege 15 secret cisco123R1(config)#


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Privilege Levels

R1> enable 5Password:R1# R1# show privilege

Current privilege level is 5R1#R1# reloadTranslating "reload"

Translating "reload"

% Unknown command or computer name, or unable to find computeraddressR1#

The enable level command is used to switchfrom Level 1 to Level 5

The show privilege command displaysThe current privilege level

The user cannot us the reload command


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Privilege Level Limitations There is no access control to specific interfaces, ports, logical

interfaces, and slots on a router Commands available at lower privilege levels are always

executable at higher levels. Commands specifically set on a higher privilege level are not

available for lower-privileged users. Assigning a command with multiple keywords to a specific

privilege level also assigns any commands associated with thefirst keywords to the same privilege level.


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Role-Based CLI Controls which commands are available to specific roles Different views of router configurations created for different

users providing: Security: Defines the set of CLI commands that is accessible by a

particular user by controlling user access to configure specific ports,logical interfaces, and slots on a router

Availability: Prevents unintentional execution of CLI commands byunauthorized personnel

Operational Efficiency: Users only see the CLI commands applicable tothe ports and CLI to which they have access


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Role-Based Views Root View

To configure any view for the system, the administrator must be in theroot view. Root view has all of the access privileges as a user who haslevel 15 privileges.

CLI View

A specific set of commands can be bundled into a CLI view. Each viewmust be assigned all commands associated with that view and there isno inheritance of commands from other views. Additionally,commands may be reused within several views.

SuperviewAllow a network administrator to assign users and groups of usersmultiple CLI views at once instead of having to assign a single CLI viewper user with all commands associated to that one CLI view.


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Role-Based Views


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Creating and Managing a View1. Enable aaa with the global configuration command aaa new-model .

Exit, and enter the root view with the command enable view command .

2. Create a view using the parser view view-name command.3. Assign a secret password to the view using the secret encrypted-

password command. 4. Assign commands to the selected view using the parser-mode{ include | include-exclusive | exclude } [ all ][ interface interface-name | command] command in viewconfiguration mode.

5. Exit the view configuration mode by typing the command exit .


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View Commandsrouter# enable [view [ view-name ]] Command is used to enter the CLI view.

Parameter Description

view Enters view, which enables users to configure CLI views.This keyword is required if you want to configure a CLI view.

view-name (Optional) Enters or exits a specified CLI view.This keyword can be used to switch from one CLI view toanother CLI view.

router(config)# parser view view-name

Creates a view and enters view configuration mode.router(config-view)# secret encrypted-password

Sets a password to protect access to the View. Password must be created immediately after creating a view


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Creating and Managing a Superview

1. Create a view using the parser viewview-name superview command andenter superview configuration mode.

2. Assign a secret password to the view usingthe secret encrypted-password command.

3. Assign an existing view using the viewview-name command in view configurationmode.

4. Exit the superview configuration mode bytyping the command exit .


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Running Config Views


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Running Config SUPERVIEWS


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Verifying a ViewR1# show parser view

No view is active ! Currently in Privilege Level Context

R1#

R1# enable view

Password:

*Mar 1 10:38:56.233: %PARSER-6-VIEW_SWITCH: successfully set to view 'root'.R1#

R1# show parser view

Current view is 'root'

R1#

R1# show parser view all

Views/SuperViews Present in System:

SHOWVIEW

VERIFYVIEW


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CLI Commands

router(config)#secure boot-image

Enables Cisco IOS image resilience. Prevents the IOS image from being

deleted by a malicious user.

secure boot-configrouter(config)#

Takes a snapshot of the router running configuration and securely

archives it in persistent storage.


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Restoring Primary bootset

To restore a primary bootset from a secure archive:1. Reload the router using the reload command.2. From ROMMON mode, enter the dir command to list the contents of

the device that contains the secure bootset file. The device name can befound in the output of the show secure bootset command.

3. Boot up the router using the secure bootset image using the bootcommand with the filename found in step 2. Once the compromisedrouter boots, proceed to privileged EXEC mode and restore theconfiguration.

4. Enter global configuration mode using conf t . 5. Restore the secure configuration to the supplied filename using the

secure boot-config restore filename .


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Password Recovery Procedures

1. Connect to the console port. 2. Use the show version command to view and record the

configuration register3. Use the power switch to turn off the router, and then turn the router

back on.4. Press Break on the terminal keyboard within 60 seconds of power up to

put the router into ROMmon.5. At the rommon 1> prompt Type config 0x2142 .6. Type rese t at the rommon 2> prompt. The router reboots, but

ignores the saved configuration.7. Type no after each setup question, or press Ctrl-C to skip the initial

setup procedure.8. Type enable at the Router> prompt.


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Password Recovery Procedures, 2

9. Type copy startup-config running-config to copy theNVRAM into memory.

10. Type show running-config .11. Enter global configuration and type the enable secret command to

change the enable secret password.12. Issue the no shutdown command on every interface to be used. Once

enabled, issue a show ip interface brief command. Everyinterface to be used should display up up.

13. Type config-register configuration_register_setting .The configuration_register_setting is either the value recorded in Step 2 or0x2102 .

14. Save configuration changes using the copy running-configstartup-config command.


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Preventing Password RecoveryR1(config)# no service password-recovery

WARNING:Executing this command will disable password recovery mechanism.Do not execute this command without another plan for password recovery.Are you sure you want to continue? [yes/no]: yesR1(config)

R1# sho runBuilding configuration...

Current configuration : 836 bytes!version 12.4service timestamps debug datetime msecservice timestamps log datetime msecservice password-encryptionno service password-recovery

System Bootstrap, Version 12.4(13r)T, RELEASE SOFTWARE (fc1)Technical Support: http://www.cisco.com/techsupportCopyright (c) 2006 by cisco Systems, Inc.PLD version 0x10GIO ASIC version 0x127c1841 platform with 131072 Kbytes of main memoryMain memory is configured to 64 bit mode with parity disabled

PASSWORD RECOVERY FUNCTIONALITY IS DISABLED

program load complete, entry point: 0x8000f000, size: 0xcb80


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Implementing Secure Management Configuration Change Management

Know the state of critical network devices Know when the last modifications occurred Ensure the right people have access when new management

methodologies are adopted Know how to handle tools and devices no longer used

Automated logging and reporting of information fromidentified devices to management hosts

Available applications and protocols like SNMP


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Secure Management and Reporting

When logging and managing information, theinformation flow between management hostsand the managed devices can take two paths:

Out-of-band (OOB): Information flows on adedicated management network on which noproduction traffic resides.

In-band: Information flows across an enterpriseproduction network, the Internet, or both usingregular data channels.


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Factors to Consider

OOB management appropriate for largeenterprise networks

In-band management recommended insmaller networks providing a more cost-effective security deployment

Be aware of security vulnerabilities of usingremote management tools with in-bandmanagement


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Using Syslog

Implementing Router Logging Syslog Configuring System Logging Enabling Syslog using SDM/CCP


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Syslog

Syslog servers: Known as log hosts, these systems accept andprocess log messages from syslog clients. Syslog clients: Routers or other types of equipment that

generate and forward log messages to syslog servers.

e0/010.2.1.1 e0/1

10.2.2.1e0/210.2.3.1

User 10.2.3.3

Public WebServer

10.2.2.3

MailServer

10.2.2.4

AdministratorServer10.2.2.5

SyslogServer 10.2.3.2

Protected LAN10.2.3.0/24

DMZ LAN 10.2.2.0/24

Syslog Client

R3


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Configuring System Logging

R3(config)# logging 10.2.2.6R3(config)# logging trap informationalR3(config)# logging source-interface loopback 0R3(config)# logging on

1. Set the destination logging host

2. Set the log severity (trap) level

3. Set the source interface4. Enable logging

Turn logging on and off using thelogging buffered , loggingmonitor , and logging commands


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Enabling Syslog Using SDM/CCP1. Choose Configure > Additional Tasks > Router Properties > Logging

2. Click Edit

3. Check Enable Logging

Level and choose thedesired logging level

4. Click Add, and enteran IP address of alogging host

5. Click OK

h


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Monitor Logging with SDM

1. Choose Monitor > Logging

4. Monitor the messages, update thescreen to show the most current logentries, and clear all syslog messagesfrom the router log buffer

2. See the logging hosts to which

the router logs messages

3. Choose the minimum severity level

M i L i R l


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Monitor Logging Remotely

Logs can easily be viewed throughthe SDM, or for easier use,through a syslog viewer on anyremote system.

There are numerous Free remote

syslog viewers, Kiwi is relativelybasic and free. Configure the router/switch/etc to

send logs to the PCs ip addressthat has kiwi installed.

Kiwi automatically listens forsyslog messages and displaysthem.


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SNMP Developed to manage nodes, such as servers, workstations,

routers, switches, hubs, and security appliances on an IPnetwork

All versions are Application Layer protocols that facilitate theexchange of management information between networkdevices

Part of the TCP/IP protocol suite Enables network administrators to manage network

performance, find and solve network problems, and plan for

network growth Three separate versions of SNMP


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SNMPv3

Agent may enforce access control to restrict each principal to certainactions on certain portions of its

data.

Managed Node

Managed Node

Managed Node

Managed NodeMessages may be

encrypted to ensure privacy

NMS

NMS

Transmissions from manager to agent

may be authenticated to guarantee theidentity of the sender and the integrity and timeliness of a message.

Encrypted Tunnel


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Security Levels noAuth: Authenticates a packet by a string match of the

username or community string auth: Authenticates a packet by using either the Hashed

Message Authentication Code (HMAC) with Message Digest 5(MD5) method or Secure Hash Algorithms (SHA) method.

Priv: Authenticates a packet by using either the HMAC MD5 orHMAC SHA algorithms and encrypts the packet using the DataEncryption Standard (DES), Triple DES (3DES), or AdvancedEncryption Standard (AES) algorithms.


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Trap Receivers

1. Click Edit

2. Click Add

3. Enter the IP address or

the hostname of thetrap receiver and thepassword

4. Click OK6. When the trap receiver listis complete, click OK

5. To edit or delete an existing trap receiver,choose a trap receiver from the trapreceiver list and click Edit or Delete


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Timekeeping Pulling the clock time from the Internet means that unsecured packets are

allowed through the firewall Many NTP servers on the Internet do not require any authentication of

peers Devices are given the IP address of NTP masters. In an NTP configured

network, one or more routers are designated as the master clock keeper(known as an NTP Master) using the ntp master global configurationcommand.

NTP clients either contact the master or listen for messages from themaster to synchronize their clocks. To contact the server, use the ntpserver ntp-server-address command.

In a LAN environment, NTP can be configured to use IP broadcastmessages instead, by using the ntp broadcast client command.


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Enabling NTP1. Choose Configure > Additional Tasks > Router Properties > NTP/SNTP

2. Click Add

3. Add an NTP server by

name or by IP address

4. Choose the interface thatthe router will use tocommunicate with the

NTP server

5. Check Prefer if this NTPserver is a preferredserver (more than one isallowed)

6. If authentication is used,check Authentication Keyand enter the key number,the key value, and confirmthe key value.

7. Click OK


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SDM Security Audit

Perform Security Auditletting the administratorchoose configurationchanges to implement

One-Step Lockdownautomatically makes allrecommended security-related configurationchanges

Security Audit Wizard


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Security Audit Wizard

Compares router configurationagainst recommended settings:

Shut down unneeded servers Disable unneeded services Apply the firewall to the outside

interfaces Disable or harden SNMP Shut down unused interfaces Check password strength Enforce the use of ACLs


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Cisco AutoSecure Initiated from CLI and executes a script. The

AutoSecure feature first makesrecommendations for fixing securityvulnerabilities, and then modifies the securityconfiguration of the router.

Can lockdown the management planefunctions and the forwarding plane services

and functions of a router Used to provide a baseline security policy on a

new router


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Auto Secure Command

Command to enable the Cisco AutoSecurefeature setup: auto secure [no-interact]

In Interactive mode, the router prompts withoptions to enable and disable services andother security features. This is the default

mode but can also be configured using theauto secure ful l command.


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Auto Secure Command

R1# auto secure ?

firewall AutoSecure Firewall

forwarding Secure Forwarding Planefull Interactive full session of AutoSecure

login AutoSecure Login

management Secure Management Plane

no-interact Non-interactive session of AutoSecure

ntp AutoSecure NTP

ssh AutoSecure SSH

tcp-intercept AutoSecure TCP Intercept

R1#

auto secure [no-interact | full] [forwarding | management ][ntp | login | ssh | firewall | tcp-intercept]

router#

Cisco One step Lockdown


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Cisco One-step Lockdown

Tests router configurationfor any potential securityproblems and automatically

makes the necessaryconfiguration changes tocorrect any problems found


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