Lab 216 - ACL Matching Even Network Numbers

Prerequisites: CCNP level skills.

Topology

Pic 1. Topology Diagram.

Task 1

On R5 configure loopback interfaces with the following addresses:

• Lo1: 150.1.20.5/24
• Lo2: 150.1.21.5/24
• Lo3: 150.1.22.5/24
• Lo4: 150.1.23.5/24

Advertise the subnets into EIGRP AS 1.

Task 2
For security reasons configure EIGRP update filtering on R2 so that it accepts the odd subnets configured on R5 in Task 1. Use standard ACL to match the interesting subnets. Use the fewest lines possible.

Solution

Task 1

On R5 configure loopback interfaces with the following addresses:

• Lo1: 150.1.20.5/24
• Lo2: 150.1.21.5/24
• Lo3: 150.1.22.5/24
• Lo4: 150.1.23.5/24

Advertise the subnets into EIGRP AS 1.

R5 Config:
!
interface Loopback1
 ip address 150.1.20.5 255.255.255.0
!
interface Loopback2
 ip address 150.1.21.5 255.255.255.0
!
interface Loopback3
 ip address 150.1.22.5 255.255.255.0
!
interface Loopback4
 ip address 150.1.23.5 255.255.255.0
!
router eigrp 1
 network 10.0.5.5 0.0.0.0
 network 150.1.0.0
 network 172.16.215.5 0.0.0.0
 no auto-summary
!

Task 2

Task 2
For security reasons configure EIGRP update filtering on R2 so that it accepts the odd subnets configured on R5 in Task 1. Use standard ACL to match the interesting subnets. Use the fewest lines possible.

Pic. 2 - Routing Table on R2 Before Filtering.

R2 Config:
!
access-list 5 deny   150.1.20.0 0.0.2.0
access-list 5 permit any
!
router eigrp 1
 network 10.0.2.2 0.0.0.0
 network 172.16.27.2 0.0.0.0
 network 172.16.123.2 0.0.0.0
 distribute-list 5 in Serial0/0
 no auto-summary
!

Verification:

Pic. 3 - Routing Table on R2 After Filtering.

Explanation:
20 - 000101000   
22 - 000101010

The highlighted bit is the only one that changes. It should be masked using 1 (ignore: value=2). All the remaining bits do not change, so they should be masked with 0 (check).

After verification, remove ACL configured in Task 2.