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You have configured ACLs on your router. A partial configuration for the router is shown below:

hostname RouterA
!
interface FastEthernet0/0
ip address
speed auto
duplex auto
!
interface FastEthernet0/1
ip address
speed auto
duplex auto
!
interface Serial0/1/0
ip address
encapsulation ppp
ip access-group 107 in
!
access-list 107 deny ip any
access-list 107 deny ip any
access-list 107 permit ip any any
!

You want to block any traffic received on S0/1/0 that has a source address that appears to be coming from the two internal networks. However, you find that no traffic is being accepted on the S0/1/0 interface.

What should you do?

User Fedor
by
7.9k points

1 Answer

1 vote

Final Answer:

To resolve the issue of no traffic being accepted on the S0/1/0 interface, you should correct the ACL (Access Control List) configuration. The duplicate "deny ip any" statements in access-list 107 are preventing any traffic from matching the subsequent "permit ip any any" statement. Remove the redundant deny statements to allow traffic through the specified interface.

Step-by-step explanation:

The problem in the provided ACL configuration lies in the duplicate "deny ip any" statements within access-list 107. When a packet is received on interface Serial0/1/0, it undergoes ACL processing. The first "deny ip any" statement blocks all traffic, and the second one does the same, leaving no opportunity for the subsequent "permit ip any any" statement to take effect. To address this, remove the redundant "deny ip any" statements, ensuring that the ACL allows the desired traffic.

By correcting the ACL, you ensure that traffic received on interface Serial0/1/0 is evaluated according to the specified criteria. The ACL should be structured to first deny traffic from undesired sources and then permit the remaining traffic. Removing the redundant deny statements allows the router to consider the subsequent "permit ip any any" statement, which permits all IP traffic not explicitly denied by previous ACL entries.

In network configurations, careful attention to ACL syntax and logic is crucial to achieving the intended security policies without inadvertently blocking desired traffic. Regularly reviewing and testing ACLs help ensure that they function as intended and do not inadvertently disrupt network services

User SolidMercury
by
7.8k points