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For this activity, you have two tasks:
Find two instruction manuals, steps, etc., one for NAT configuration and a second one for firewall configuration.
Create a set of rules for a firewall used in a hypothetical business network.
One of the most popular network technology developers is Cisco, so we’ll use it for this activity. Go online and search the web for instructions on how to perform NAT configuration for modern Cisco routers. Make sure the site is an OFFICIAL Cisco site. Create an offline version of the information. (Either copy and paste it into a text document, or save the web page) Create a second text document that contains the full URL for the source of the information.
Next, perform the same search for the firewall configuration of Cisco devices. Once again, copy and paste the instructions you find, or save the webpage. Add the full URL for this site to the text document, which already has the NAT configuration site URL. You may have this information from a prior activity if you are using a Cisco router; if so, you can use the same documents or links, if appropriate.
Finally, let’s put some of these ideas into practice and come up with rules that would make sense for a hypothetical small business network (i.e., 20 or so staff working in various parts of the company such as sales, management, IT department, and accounting/human resources). In your document listing the two URLs for NAT and firewall configuration, add two rules that would make sense for the firewall of an intranet used by the accounting staff to fulfill payroll. The two rules should include the following information:
The purpose of the firewall
The affected service, application, or information
Who will be affected by the rules
The rules themselves
Just to make it more interesting, assume that the firewall already has one rule: All traffic, by default, is blocked. You should also assume that you’ve already configured the network to audit all logs.
The rules can be explained in general terms—that is, you don’t need to write the specific line of code that would be required—and you should identify specific port numbers. Examples of rules can easily be found online; just make sure the rules are suitable for a small business environment.
Include the following materials in your submission for this activity:
One text file that lists two URLs (for NAT configuration and firewall configuration) and two examples of firewall rules
Two files that are accessible offline and include instructions for NAT configuration and firewall configuration (The files should be pulled from official Cisco support information and can be provided in TXT or HTML formats, or even PDF if you pull an instruction manual offline.)
All Answers 1
Answered by
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Below are the deliverables you requested. I’ve provided:
- Two official Cisco URLs (one NAT config doc, one firewall config doc).
- A “text file” listing the two URLs plus two firewall-rule examples for the accounting/payroll intranet (each rule includes purpose, affected service, who, and the rule itself).
- Two offline-ready instruction blocks (you can copy/paste each block into a .txt file). The first block contains step-by-step NAT configuration examples for Cisco IOS routers (PAT/Static NAT). The second block contains practical firewall configuration examples for Cisco devices (ACL on IOS / ASA example and a short zone-based-policy example). These instruction blocks are written so you can save them exactly as offline files.
1) Two official Cisco URLs
- NAT configuration (Cisco IOS NAT overview and configuration examples):
https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipaddr_nat/configuration/15-mt/ipaddr-nat-15-mt-book/intro-nat.html
- Firewall configuration (Cisco firewall documentation — ASA and IOS firewall guides; pick the ASA CLI/config guide or IOS zone-based firewall docs from Cisco):
Cisco ASA Series Firewall CLI Configuration Guide (example):
https://www.cisco.com/c/en/us/td/docs/security/asa/asa912/configuration/guide/asa_912_cli_config/index.html
OR (IOS Zone-Based Policy Firewall):
https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/fw/command/fw-book/fw-book.html
(If you prefer, save the two chosen pages above as offline files: open the page in a browser → File → Save As → choose “Webpage, HTML only” or “Text” or copy/paste the page contents into a text file.)
2) Text file content: URLs + Two firewall rules for the accounting (payroll) intranet
(Copy/paste this into a text file named e.g., urls_and_rules.txt)
- NAT URL:
https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipaddr_nat/configuration/15-mt/ipaddr-nat-15-mt-book/intro-nat.html
- Firewall URL (ASA CLI / IOS firewall):
https://www.cisco.com/c/en/us/td/docs/security/asa/asa912/configuration/guide/asa_912_cli_config/index.html
https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/fw/command/fw-book/fw-book.html
Firewall rule set for Accounting (payroll) intranet
(Assumptions: default policy = deny all; logging/auditing already enabled. Internal network subnets used as examples.)
Rule 1 — Allow accounting staff to access internal payroll web application (HTTPS)
- Purpose:
Allow accounting personnel to access the internal payroll web application securely.
- Affected service/application/information:
Payroll web application (HTTPS) — sensitive payroll data; web portal.
- Who will be affected:
Accounting staff (workstations in accounting subnet 10.1.10.0/24) and the payroll server (10.1.20.10).
- Rule (general terms):
Permit TCP from source subnet 10.1.10.0/24 to destination host 10.1.20.10 on TCP port 443 (HTTPS). Log matches. Apply rule on the internal interface (firewall/ACL direction: permit inbound from accounting zone to payroll server). Example conditions: only allow during business hours if desired (time-based ACL optional).
Summary:
- Action: PERMIT + LOG
- Source: 10.1.10.0/24 (Accounting)
- Destination: 10.1.20.10 (Payroll server)
- Protocol/Port: TCP / 443
- Other: Stateful inspection (allow return traffic related to session)
Rule 2 — Allow payroll server to send payroll batches to bank SFTP endpoint
- Purpose:
Permit the payroll server to securely upload payroll files to the bank’s SFTP gateway (outbound).
- Affected service/application/information:
File transfer of payroll data to the bank via SFTP (SSH over TCP port 22). Highly sensitive financial data.
- Who will be affected:
Payroll server (10.1.20.10), bank’s payment gateway(s) (restrict to specific bank IP(s) e.g., 198.51.100.25).
- Rule (general terms):
Permit TCP from source host 10.1.20.10 to destination host 198.51.100.25 on TCP port 22 (SFTP/SSH). Log matches. Only outbound from payroll server to specified bank IP(s). Deny all other outbound connections to external financial endpoints unless explicitly allowed.
Summary:
- Action: PERMIT + LOG
- Source: 10.1.20.10 (Payroll server)
- Destination: 198.51.100.25 (Bank SFTP gateway — replace with actual bank IP(s))
- Protocol/Port: TCP / 22
- Other: NAT may be applied (see NAT rules) so that bank sees a permitted public IP; use static NAT or PAT as appropriate.
Notes:
- Because default is to deny all traffic, you must explicitly permit the flows above.
- Ensure firewall logging is enabled for these rules (for audit and troubleshooting).
- Limit source/destination to exact subnets or hosts and to specific ports only — avoid wide-open permits.
- If bank provides a range of IPs, enumerate and allow only those IPs and ports.
- Consider using time-based ACL entries (if supported) to restrict access to business hours for interactive access.
3) Offline file #1: NAT configuration (copy everything below into nat_instructions.txt)
--- Begin nat_instructions.txt ---
Title: Cisco IOS NAT configuration — Basic examples (PAT / Static NAT / NAT Pool)
Source (official Cisco docs): https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipaddr_nat/configuration/15-mt/ipaddr-nat-15-mt-book/intro-nat.html
Purpose:
This file contains concise, commonly-used Cisco IOS NAT configuration examples: dynamic PAT (overload), static NAT, and NAT pool example. Adjust interface names, IPs, and ACL numbers to match your environment.
1) Basic steps for NAT Overload (PAT) — translate many private addresses to a single public interface IP
Assumptions:
- Internal (inside) interface: GigabitEthernet0/1 — internal network 10.1.0.0/24
- External (outside) interface: GigabitEthernet0/0 — has public IP assigned by ISP
Commands (entered in global/config mode):
a) Configure interfaces and mark NAT inside/outside:
interface GigabitEthernet0/1
ip address 10.1.0.1 255.255.255.0
ip nat inside
!
interface GigabitEthernet0/0
ip address 198.51.100.10 255.255.255.248
ip nat outside
!
b) Create an access-list to identify inside local addresses to be translated:
access-list 10 permit 10.1.0.0 0.0.0.255
c) Configure PAT using the outside interface IP:
ip nat inside source list 10 interface GigabitEthernet0/0 overload
Explanation:
- The ACL (10) identifies internal addresses.
- The ip nat inside source list ... interface ... overload command causes many inside hosts to share the interface public IP (PAT).
2) Static NAT (map a single internal host to a public IP)
Use when an internal host (e.g., a server) must be reachable from outside.
Example — map internal server 10.1.20.10 to public IP 198.51.100.20:
ip nat inside source static 10.1.20.10 198.51.100.20
(If mapping a port, e.g., public TCP 443 to internal 10.1.20.10:443)
ip nat inside source static tcp 10.1.20.10 443 198.51.100.20 443
3) NAT pool example (less common than PAT, but shown for completeness)
Define a pool of public addresses and use an ACL to select inside hosts.
ip nat pool mypool 198.51.100.21 198.51.100.30 netmask 255.255.255.248
access-list 11 permit 10.1.0.0 0.0.0.255
ip nat inside source list 11 pool mypool
4) Verification and troubleshooting
- show ip nat translations
- show ip nat statistics
- debug ip nat detailed (use with caution)
Notes / Best practices:
- Mark interfaces correctly (ip nat inside / ip nat outside).
- Use ACLs to limit what is translated.
- For servers that must be accessible from outside, use static NAT.
- For client Internet access, use PAT (overload).
- Consider security: NAT does not replace firewall rules; combine with ACLs/firewall policies.
--- End nat_instructions.txt ---
4) Offline file #2: Firewall configuration instructions (copy everything below into firewall_instructions.txt)
--- Begin firewall_instructions.txt ---
Title: Cisco Firewall configuration examples — IOS ACLs, ASA ACL + access-group, brief Zone-Based Policy example
Sources (official Cisco docs):
- ASA CLI Configuration Guide: https://www.cisco.com/c/en/us/td/docs/security/asa/asa912/configuration/guide/asa_912_cli_config/index.html
- IOS Zone-Based Policy Firewall documentation: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/fw/command/fw-book/fw-book.html
Purpose:
This file gives concrete, usable firewall configuration examples for a small business. It shows:
- IOS standard access-list/extended ACL usage for internal firewalling
- Cisco ASA ACL and access-group example
- Short example of IOS Zone-Based Policy Firewall (ZBFW) configuration steps
Assumptions:
- Default policy = deny all
- Logging/auditing is enabled (syslog, local logging, or remote collector)
- Use the specific host/subnet addresses and interfaces below as examples; replace with your real addresses.
A) Cisco IOS simple extended ACL (host/subnet-based firewalling)
Scenario: Permit Accounting subnet to reach payroll server on HTTPS only.
Commands (global config):
! Create extended ACL:
ip access-list extended ACCOUNTING_TO_PAYROLL
permit tcp 10.1.10.0 0.0.0.255 host 10.1.20.10 eq 443
deny ip any host 10.1.20.10
!
! Apply the ACL to the inbound direction of the inside interface (or appropriate interface)
interface GigabitEthernet0/1
ip access-group ACCOUNTING_TO_PAYROLL in
!
Notes:
- This ACL permits only TCP/443 from accounting subnet to payroll server.
- Because stateful inspection is limited in basic IOS ACLs, ensure return traffic is allowed (if ACL applied on outside interface, allow established traffic). In many setups, stateful inspection is provided by ASA or zone-based firewall; plain IOS extended ACLs are stateless.
B) Cisco ASA example (recommended for a small-site firewall appliance)
Scenario 1: Permit Accounting to Payroll server on HTTPS (inside to inside traffic routed via ASA)
Assume inside interface is 'inside', outside is 'outside'. Use ASA access-list and apply to interface with access-group.
! Create ACL
access-list IN_SIDE_ACL extended permit tcp 10.1.10.0 255.255.255.0 host 10.1.20.10 eq 443
access-list IN_SIDE_ACL extended permit tcp host 10.1.20.10 host 198.51.100.25 eq 22 ! if payroll server needs to contact bank
! (Add explicit deny/permit lines as needed — ASA has a global implicit deny)
! Apply ACL to interface (direction depends on traffic flow)
access-group IN_SIDE_ACL in interface inside
! Verify and logging
show access-list IN_SIDE_ACL
logging enable
logging buffered informational
Notes:
- ASA is stateful by default: permit will allow return traffic.
- Add nat rules if needed for server to reach external bank (static NAT or PAT). Example static NAT (ASA 9.x object NAT):
object network PAYROLL-SERVER
host 10.1.20.10
nat (inside,outside) static 198.51.100.30
C) IOS Zone-Based Policy Firewall (ZBFW) — short example (stateful)
Overview:
- Create class-map to define traffic (match access-list)
- Create policy-map to define actions (inspect)
- Assign policy to a zone-pair between zones (e.g., accounting-zone to payroll-zone)
Example (simple):
! Define zones
zone security ACCOUNTING
zone security PAYROLL
! Put interfaces in zones
interface GigabitEthernet0/1
zone-member security ACCOUNTING
!
interface GigabitEthernet0/2
zone-member security PAYROLL
!
! Create an ACL to match HTTPS
ip access-list extended TO_PAYROLL_HTTPS
permit tcp 10.1.10.0 0.0.0.255 host 10.1.20.10 eq 443
! Class-map matching the ACL
class-map match-any C_TO_P_HTTPS
match access-group name TO_PAYROLL_HTTPS
! Policy-map to inspect and allow
policy-map type inspect PM_C_TO_P
class C_TO_P_HTTPS
inspect tcp
! Create zone-pair (ACCOUNTING -> PAYROLL)
zone-pair security ZP_ACCOUNTING_TO_PAYROLL source ACCOUNTING destination PAYROLL
service-policy type inspect PM_C_TO_P
Notes:
- ZBFW is stateful and more powerful than simple ACLs.
- Use logging and monitoring commands to audit matches.
Logging and Auditing:
- Ensure logging is enabled and forwarded to a log collector (syslog server) for retention and auditing.
- Typical commands:
- show logging
- (ASA) show logging
- (IOS) logging host <ip> ; logging trap informational
Best practices:
- Use least privilege: only allow the minimal set of ports and IPs required.
- Permit specific source hosts/subnets and specific destination hosts/ports; avoid any/any permits.
- Log permitted and denied packets for audit.
- Combine NAT (for external reachability) with ACLs/ASA policies to control what is allowed.
- Test rules in a staged environment or use time-limited exceptions to verify before broad rollout.
--- End firewall_instructions.txt ---
4) How to produce the actual offline files (if you need explicit steps)
- Open a plain text editor (Notepad on Windows, TextEdit in plain text mode on macOS, or any editor).
- For the NAT instructions: copy the nat_instructions.txt block above and paste into the editor. Save as nat_instructions.txt.
- For the firewall instructions: copy the firewall_instructions.txt block above and paste into the editor. Save as firewall_instructions.txt.
- For the URLs + rules: copy the “Text file content” section and save as urls_and_rules.txt.
Final notes / recommendations
- Replace example IP addresses (10.1.x.x, 198.51.100.x, 198.51.100.25) with your actual network and bank IP addresses.
- If you use ASA, consult the exact ASA version-specific docs from Cisco (ASA configuration commands changed slightly across versions). Use the ASA CLI guide URL provided above for the ASA version you run.
- For audit/compliance, export firewall logs regularly and keep them in a secure, centralized log server.
If you want, I can:
- Produce the exact one-line ACL rules in IOS or ASA CLI format for the two rules (with exact command lines) given your real subnets/IPs and interfaces; or
- Produce a ready-to-save ZIP containing three text files (urls_and_rules.txt, nat_instructions.txt, firewall_instructions.txt) if you tell me how you prefer to receive the files.
- Two official Cisco URLs (one NAT config doc, one firewall config doc).
- A “text file” listing the two URLs plus two firewall-rule examples for the accounting/payroll intranet (each rule includes purpose, affected service, who, and the rule itself).
- Two offline-ready instruction blocks (you can copy/paste each block into a .txt file). The first block contains step-by-step NAT configuration examples for Cisco IOS routers (PAT/Static NAT). The second block contains practical firewall configuration examples for Cisco devices (ACL on IOS / ASA example and a short zone-based-policy example). These instruction blocks are written so you can save them exactly as offline files.
1) Two official Cisco URLs
- NAT configuration (Cisco IOS NAT overview and configuration examples):
https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipaddr_nat/configuration/15-mt/ipaddr-nat-15-mt-book/intro-nat.html
- Firewall configuration (Cisco firewall documentation — ASA and IOS firewall guides; pick the ASA CLI/config guide or IOS zone-based firewall docs from Cisco):
Cisco ASA Series Firewall CLI Configuration Guide (example):
https://www.cisco.com/c/en/us/td/docs/security/asa/asa912/configuration/guide/asa_912_cli_config/index.html
OR (IOS Zone-Based Policy Firewall):
https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/fw/command/fw-book/fw-book.html
(If you prefer, save the two chosen pages above as offline files: open the page in a browser → File → Save As → choose “Webpage, HTML only” or “Text” or copy/paste the page contents into a text file.)
2) Text file content: URLs + Two firewall rules for the accounting (payroll) intranet
(Copy/paste this into a text file named e.g., urls_and_rules.txt)
- NAT URL:
https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipaddr_nat/configuration/15-mt/ipaddr-nat-15-mt-book/intro-nat.html
- Firewall URL (ASA CLI / IOS firewall):
https://www.cisco.com/c/en/us/td/docs/security/asa/asa912/configuration/guide/asa_912_cli_config/index.html
https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/fw/command/fw-book/fw-book.html
Firewall rule set for Accounting (payroll) intranet
(Assumptions: default policy = deny all; logging/auditing already enabled. Internal network subnets used as examples.)
Rule 1 — Allow accounting staff to access internal payroll web application (HTTPS)
- Purpose:
Allow accounting personnel to access the internal payroll web application securely.
- Affected service/application/information:
Payroll web application (HTTPS) — sensitive payroll data; web portal.
- Who will be affected:
Accounting staff (workstations in accounting subnet 10.1.10.0/24) and the payroll server (10.1.20.10).
- Rule (general terms):
Permit TCP from source subnet 10.1.10.0/24 to destination host 10.1.20.10 on TCP port 443 (HTTPS). Log matches. Apply rule on the internal interface (firewall/ACL direction: permit inbound from accounting zone to payroll server). Example conditions: only allow during business hours if desired (time-based ACL optional).
Summary:
- Action: PERMIT + LOG
- Source: 10.1.10.0/24 (Accounting)
- Destination: 10.1.20.10 (Payroll server)
- Protocol/Port: TCP / 443
- Other: Stateful inspection (allow return traffic related to session)
Rule 2 — Allow payroll server to send payroll batches to bank SFTP endpoint
- Purpose:
Permit the payroll server to securely upload payroll files to the bank’s SFTP gateway (outbound).
- Affected service/application/information:
File transfer of payroll data to the bank via SFTP (SSH over TCP port 22). Highly sensitive financial data.
- Who will be affected:
Payroll server (10.1.20.10), bank’s payment gateway(s) (restrict to specific bank IP(s) e.g., 198.51.100.25).
- Rule (general terms):
Permit TCP from source host 10.1.20.10 to destination host 198.51.100.25 on TCP port 22 (SFTP/SSH). Log matches. Only outbound from payroll server to specified bank IP(s). Deny all other outbound connections to external financial endpoints unless explicitly allowed.
Summary:
- Action: PERMIT + LOG
- Source: 10.1.20.10 (Payroll server)
- Destination: 198.51.100.25 (Bank SFTP gateway — replace with actual bank IP(s))
- Protocol/Port: TCP / 22
- Other: NAT may be applied (see NAT rules) so that bank sees a permitted public IP; use static NAT or PAT as appropriate.
Notes:
- Because default is to deny all traffic, you must explicitly permit the flows above.
- Ensure firewall logging is enabled for these rules (for audit and troubleshooting).
- Limit source/destination to exact subnets or hosts and to specific ports only — avoid wide-open permits.
- If bank provides a range of IPs, enumerate and allow only those IPs and ports.
- Consider using time-based ACL entries (if supported) to restrict access to business hours for interactive access.
3) Offline file #1: NAT configuration (copy everything below into nat_instructions.txt)
--- Begin nat_instructions.txt ---
Title: Cisco IOS NAT configuration — Basic examples (PAT / Static NAT / NAT Pool)
Source (official Cisco docs): https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipaddr_nat/configuration/15-mt/ipaddr-nat-15-mt-book/intro-nat.html
Purpose:
This file contains concise, commonly-used Cisco IOS NAT configuration examples: dynamic PAT (overload), static NAT, and NAT pool example. Adjust interface names, IPs, and ACL numbers to match your environment.
1) Basic steps for NAT Overload (PAT) — translate many private addresses to a single public interface IP
Assumptions:
- Internal (inside) interface: GigabitEthernet0/1 — internal network 10.1.0.0/24
- External (outside) interface: GigabitEthernet0/0 — has public IP assigned by ISP
Commands (entered in global/config mode):
a) Configure interfaces and mark NAT inside/outside:
interface GigabitEthernet0/1
ip address 10.1.0.1 255.255.255.0
ip nat inside
!
interface GigabitEthernet0/0
ip address 198.51.100.10 255.255.255.248
ip nat outside
!
b) Create an access-list to identify inside local addresses to be translated:
access-list 10 permit 10.1.0.0 0.0.0.255
c) Configure PAT using the outside interface IP:
ip nat inside source list 10 interface GigabitEthernet0/0 overload
Explanation:
- The ACL (10) identifies internal addresses.
- The ip nat inside source list ... interface ... overload command causes many inside hosts to share the interface public IP (PAT).
2) Static NAT (map a single internal host to a public IP)
Use when an internal host (e.g., a server) must be reachable from outside.
Example — map internal server 10.1.20.10 to public IP 198.51.100.20:
ip nat inside source static 10.1.20.10 198.51.100.20
(If mapping a port, e.g., public TCP 443 to internal 10.1.20.10:443)
ip nat inside source static tcp 10.1.20.10 443 198.51.100.20 443
3) NAT pool example (less common than PAT, but shown for completeness)
Define a pool of public addresses and use an ACL to select inside hosts.
ip nat pool mypool 198.51.100.21 198.51.100.30 netmask 255.255.255.248
access-list 11 permit 10.1.0.0 0.0.0.255
ip nat inside source list 11 pool mypool
4) Verification and troubleshooting
- show ip nat translations
- show ip nat statistics
- debug ip nat detailed (use with caution)
Notes / Best practices:
- Mark interfaces correctly (ip nat inside / ip nat outside).
- Use ACLs to limit what is translated.
- For servers that must be accessible from outside, use static NAT.
- For client Internet access, use PAT (overload).
- Consider security: NAT does not replace firewall rules; combine with ACLs/firewall policies.
--- End nat_instructions.txt ---
4) Offline file #2: Firewall configuration instructions (copy everything below into firewall_instructions.txt)
--- Begin firewall_instructions.txt ---
Title: Cisco Firewall configuration examples — IOS ACLs, ASA ACL + access-group, brief Zone-Based Policy example
Sources (official Cisco docs):
- ASA CLI Configuration Guide: https://www.cisco.com/c/en/us/td/docs/security/asa/asa912/configuration/guide/asa_912_cli_config/index.html
- IOS Zone-Based Policy Firewall documentation: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/fw/command/fw-book/fw-book.html
Purpose:
This file gives concrete, usable firewall configuration examples for a small business. It shows:
- IOS standard access-list/extended ACL usage for internal firewalling
- Cisco ASA ACL and access-group example
- Short example of IOS Zone-Based Policy Firewall (ZBFW) configuration steps
Assumptions:
- Default policy = deny all
- Logging/auditing is enabled (syslog, local logging, or remote collector)
- Use the specific host/subnet addresses and interfaces below as examples; replace with your real addresses.
A) Cisco IOS simple extended ACL (host/subnet-based firewalling)
Scenario: Permit Accounting subnet to reach payroll server on HTTPS only.
Commands (global config):
! Create extended ACL:
ip access-list extended ACCOUNTING_TO_PAYROLL
permit tcp 10.1.10.0 0.0.0.255 host 10.1.20.10 eq 443
deny ip any host 10.1.20.10
!
! Apply the ACL to the inbound direction of the inside interface (or appropriate interface)
interface GigabitEthernet0/1
ip access-group ACCOUNTING_TO_PAYROLL in
!
Notes:
- This ACL permits only TCP/443 from accounting subnet to payroll server.
- Because stateful inspection is limited in basic IOS ACLs, ensure return traffic is allowed (if ACL applied on outside interface, allow established traffic). In many setups, stateful inspection is provided by ASA or zone-based firewall; plain IOS extended ACLs are stateless.
B) Cisco ASA example (recommended for a small-site firewall appliance)
Scenario 1: Permit Accounting to Payroll server on HTTPS (inside to inside traffic routed via ASA)
Assume inside interface is 'inside', outside is 'outside'. Use ASA access-list and apply to interface with access-group.
! Create ACL
access-list IN_SIDE_ACL extended permit tcp 10.1.10.0 255.255.255.0 host 10.1.20.10 eq 443
access-list IN_SIDE_ACL extended permit tcp host 10.1.20.10 host 198.51.100.25 eq 22 ! if payroll server needs to contact bank
! (Add explicit deny/permit lines as needed — ASA has a global implicit deny)
! Apply ACL to interface (direction depends on traffic flow)
access-group IN_SIDE_ACL in interface inside
! Verify and logging
show access-list IN_SIDE_ACL
logging enable
logging buffered informational
Notes:
- ASA is stateful by default: permit will allow return traffic.
- Add nat rules if needed for server to reach external bank (static NAT or PAT). Example static NAT (ASA 9.x object NAT):
object network PAYROLL-SERVER
host 10.1.20.10
nat (inside,outside) static 198.51.100.30
C) IOS Zone-Based Policy Firewall (ZBFW) — short example (stateful)
Overview:
- Create class-map to define traffic (match access-list)
- Create policy-map to define actions (inspect)
- Assign policy to a zone-pair between zones (e.g., accounting-zone to payroll-zone)
Example (simple):
! Define zones
zone security ACCOUNTING
zone security PAYROLL
! Put interfaces in zones
interface GigabitEthernet0/1
zone-member security ACCOUNTING
!
interface GigabitEthernet0/2
zone-member security PAYROLL
!
! Create an ACL to match HTTPS
ip access-list extended TO_PAYROLL_HTTPS
permit tcp 10.1.10.0 0.0.0.255 host 10.1.20.10 eq 443
! Class-map matching the ACL
class-map match-any C_TO_P_HTTPS
match access-group name TO_PAYROLL_HTTPS
! Policy-map to inspect and allow
policy-map type inspect PM_C_TO_P
class C_TO_P_HTTPS
inspect tcp
! Create zone-pair (ACCOUNTING -> PAYROLL)
zone-pair security ZP_ACCOUNTING_TO_PAYROLL source ACCOUNTING destination PAYROLL
service-policy type inspect PM_C_TO_P
Notes:
- ZBFW is stateful and more powerful than simple ACLs.
- Use logging and monitoring commands to audit matches.
Logging and Auditing:
- Ensure logging is enabled and forwarded to a log collector (syslog server) for retention and auditing.
- Typical commands:
- show logging
- (ASA) show logging
- (IOS) logging host <ip> ; logging trap informational
Best practices:
- Use least privilege: only allow the minimal set of ports and IPs required.
- Permit specific source hosts/subnets and specific destination hosts/ports; avoid any/any permits.
- Log permitted and denied packets for audit.
- Combine NAT (for external reachability) with ACLs/ASA policies to control what is allowed.
- Test rules in a staged environment or use time-limited exceptions to verify before broad rollout.
--- End firewall_instructions.txt ---
4) How to produce the actual offline files (if you need explicit steps)
- Open a plain text editor (Notepad on Windows, TextEdit in plain text mode on macOS, or any editor).
- For the NAT instructions: copy the nat_instructions.txt block above and paste into the editor. Save as nat_instructions.txt.
- For the firewall instructions: copy the firewall_instructions.txt block above and paste into the editor. Save as firewall_instructions.txt.
- For the URLs + rules: copy the “Text file content” section and save as urls_and_rules.txt.
Final notes / recommendations
- Replace example IP addresses (10.1.x.x, 198.51.100.x, 198.51.100.25) with your actual network and bank IP addresses.
- If you use ASA, consult the exact ASA version-specific docs from Cisco (ASA configuration commands changed slightly across versions). Use the ASA CLI guide URL provided above for the ASA version you run.
- For audit/compliance, export firewall logs regularly and keep them in a secure, centralized log server.
If you want, I can:
- Produce the exact one-line ACL rules in IOS or ASA CLI format for the two rules (with exact command lines) given your real subnets/IPs and interfaces; or
- Produce a ready-to-save ZIP containing three text files (urls_and_rules.txt, nat_instructions.txt, firewall_instructions.txt) if you tell me how you prefer to receive the files.
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