Named ACLs – Detailed Explanation

1. What are Named ACLs?

Named Access Control Lists (ACLs) are ACLs identified by a custom name (like BLOCK_WEB) instead of a numeric value.
Purpose: Increase readability, simplify management, and enable more flexible, granular editing of ACL entries.
Named ACLs support both standard (source IP only) and extended (source, destination, protocol, port) types.

2. Difference Between Numbered and Named ACLs

Feature	Numbered ACL	Named ACL
Identification	Numeric (e.g., 10, 101)	Text name (e.g., BLOCK_HTTP)
Editing	Must delete & recreate	Edit individual lines
Sequence Numbers	Not supported	Supported
Readability	Lower	Higher
Flexibility	Lower	Higher

3. Advantages of Named ACLs

Easier to identify and manage using descriptive names.
Support for incremental editing—add, delete, or reorder entries with sequence numbers.
Work with both standard and extended ACLs.
Enable precise control over the order of rules.

4. Creating Named ACLs

Standard Named ACL Example:

ip access-list standard BLOCK_LOCAL
 permit 192.168.10.0 0.0.0.255
 deny any

Extended Named ACL Example:

ip access-list extended BLOCK_WEB
 permit tcp any host 10.0.0.1 eq 80
 deny ip any any

Enter ACL configuration submode and add rules line by line. Sequence numbers are optional but recommended for easier editing.

5. Applying Named ACLs

To interfaces (router or switch):

interface GigabitEthernet0/1
 ip access-group BLOCK_WEB in

Other uses: SVIs on Layer 3 switches, route-maps (for PBR, NAT), VPN filters, VTY lines, etc.

6. Editing Named ACLs

Adding entries with sequence numbers:

ip access-list extended BLOCK_WEB
 10 permit tcp any host 10.0.0.1 eq 80
 20 deny ip any any

Removing an entry:

ip access-list extended BLOCK_WEB
 no 10

Inserting between entries:

ip access-list extended BLOCK_WEB
 15 permit icmp any any

This adds a rule between sequence 10 and 20.

7. Viewing Named ACLs

show access-lists BLOCK_WEB — View the rules in a named ACL.
show running-config | section access-list — List all ACL definitions.

8. Named vs Numbered ACL – Functional Differences

Aspect	Named ACL	Numbered ACL
Editing	Add/remove lines, reorder with sequence numbers	Delete/recreate the whole ACL to change order
Identification	Descriptive, easier documentation	Numeric, less intuitive
Use case	Preferred for large or frequently modified lists	Simple/legacy configs or automation scripts

9. Best Practices for Named ACLs

Use descriptive names (e.g., BLOCK_TELNET, PERMIT_ADMIN).
Follow a naming convention: uppercase, underscores, concise and clear.
Comment and document the purpose of each ACL and rule.
Order rules logically—most specific first, general last.
Use sequence numbers for easy insertion and management.

10. Troubleshooting Named ACLs

Check that the ACL is applied to the correct interface and in the right direction (in/out).
Watch for overlapping/conflicting rules or missing permits (implicit deny).
Debug with:
- show access-lists BLOCK_WEB
- show ip interface [int]
Add log keyword for real-time monitoring of matches.

11. Verifying ACL Effectiveness

Check hit counts using show access-lists [name].
Use show ip interface to confirm ACL application and direction.
Test with ping, telnet, or actual application traffic.

12. Limitations and Considerations

IOS Version: Named ACLs require IOS 12.0(1) or later (most modern equipment supports them).
Entry Limits: Subject to platform/software, but supports thousands of entries on enterprise devices.
Case Sensitivity: Names may be case-sensitive on some platforms—be consistent.
Syntax: Some features (like reflexive or time-based ACLs) may have unique needs with named ACLs.

Example Scenario:
Block all HTTP access to server 10.10.10.10 but allow all other traffic.

ip access-list extended BLOCK_HTTP
 deny tcp any host 10.10.10.10 eq 80
 permit ip any any
!
interface GigabitEthernet0/2
 ip access-group BLOCK_HTTP in

This blocks HTTP to 10.10.10.10 from any source on inbound traffic, but permits all else.

Key Points and Exam Tips

Key Point	Explanation
Descriptive Names	Named ACLs are easier to identify and manage than numbered ACLs.
Sequence Numbers	Support incremental editing and precise order control.
Both Standard & Extended	Can create named ACLs for either type.
Apply to Interface	With `ip access-group [name] in\|out`
Verification	Use `show access-lists [name]` to view rules and hits.
Use Naming Conventions	Keep names clear and consistent for troubleshooting.
Test Thoroughly	Always test after editing to avoid unintentional blocks.
Document Purpose	Comment ACLs for clarity, especially in large environments.

When and Where to Use Named ACLs:
In any environment needing large, complex, or frequently updated access policies.
Ideal for: Enterprise networks, collaborative troubleshooting, and where documentation and clarity are priorities.

Named ACLs Quiz

1. What is the main advantage of Named ACLs over Numbered ACLs?

A. They use less CPU on routers B. They support only standard ACLs C. They allow easier management and incremental editing D. They do not require applying on interfaces

Correct answer is C. Named ACLs support incremental edits and are easier to manage due to descriptive names.

2. How do you start configuring a standard named ACL called “PERMIT_SALES”?

A. ip access-list extended PERMIT_SALES B. ip access-list standard PERMIT_SALES C. access-list 10 permit PERMIT_SALES D. access-list named PERMIT_SALES

Correct answer is B. Standard named ACLs use the command "ip access-list standard <name>".

3. What feature allows you to reorder or insert individual ACL rules in Named ACLs?

A. IP helper addresses B. Access Control Entries (ACEs) C. Loopback interfaces D. Sequence numbers

Correct answer is D. Sequence numbers allow inserting or reordering rules within a Named ACL.

4. Which command applies a Named ACL called BLOCK_WEB inbound on interface GigabitEthernet0/1?

A. ip access-group BLOCK_WEB in B. ip access-list BLOCK_WEB in C. access-list BLOCK_WEB in D. apply access-group BLOCK_WEB in

Correct answer is A. The correct interface-level command is "ip access-group <name> in|out".

5. How do you remove a specific ACL entry with sequence number 15 in a Named ACL?

A. delete 15 from ACL B. no access-list 15 C. no 15 D. remove 15

Correct answer is C. Use "no <sequence number>" within ACL configuration mode to remove that entry.

6. Which show command lists the entries of a Named ACL called BLOCK_WEB?

A. show running-config access-list BLOCK_WEB B. show access-lists BLOCK_WEB C. show ip interface BLOCK_WEB D. show ip access-group BLOCK_WEB

Correct answer is B. "show access-lists <name>" displays Named ACL contents and counters.

7. Which is NOT a benefit of Named ACLs compared to Numbered ACLs?

A. Higher readability B. Ability to edit individual rules C. Support for sequence numbers D. Automatically optimize routing paths

Correct answer is D. Named ACLs manage access control, not routing optimization.

8. When using Named ACLs, what is the correct way to insert a new rule between sequence numbers 10 and 20?

A. Add the rule with a sequence number 15 B. Delete the rule 20 and add a new one C. Use the command 'insert rule between 10 and 20' D. Add without sequence number; it auto-inserts

Correct answer is A. You can insert a rule by assigning it a sequence number between existing ones.

9. Which types of ACLs can be named in Cisco IOS?

A. Only standard ACLs B. Both standard and extended ACLs C. Only extended ACLs D. Named ACLs are not supported

Correct answer is B. Cisco IOS supports naming both standard and extended ACLs.

10. Why is documentation and consistent naming important for Named ACLs?

A. It improves bandwidth B. It encrypts ACL rules automatically C. It makes troubleshooting and collaboration easier D. It automatically updates rules

Correct answer is C. Clear documentation and naming help network teams understand and manage ACLs effectively.

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