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troubleshoot ACLs (processing packet with acls (the implicit deny any (A…
troubleshoot ACLs
processing packet with acls
the implicit deny any
A single-entry ACL with only one deny entry has the effect of denying all traffic. At least one permit ACE must be configured in an ACL or all traffic is blocked.
the order of ace in acl
The configuration in Figure 2 of ACL 4 has the same two statements but in reverse order. This is a valid sequence of statements because the first statement refers a specific host, not a range of hosts.
cisco ios reorders standard acl
The order in which standard ACEs are entered may not be the order that they are stored, displayed, or processed by the router.
routing proceses in acl
The figure shows the logic of routing and ACL processes. When a packet arrives at a router interface, the router process is the same, whether ACLs are used or not. As a frame enters an interface, the router checks to see whether the destination Layer 2 address matches its interface Layer 2 address, or whether the frame is a broadcast frame.
common IPV4 standard acls
Troubleshooting Standard IPv4 ACLs
although PC2 cannot access the File Server, neither can PC1. When viewing the output of the show access-list command, only PC2 is explicitly denied. However, there is no permit statement allowing other access.
All access out the G0/0 interface to the 192.168.30.0/24 LAN is currently implicitly denied. Add a statement to ACL 10 to permit all other traffic, as shown in Figure 2. PC1 should now be able to access the file server.
Troubleshooting Standard IPv4 ACLs - Example 2
PC2 cannot access PC1. Nor can it access the Internet through R2. When viewing the output of the show access-list command, you can see that PC2 is matching the deny statement. ACL 20 seems to be configured correctly.
the show run command filtered to view the interface configurations reveals that ACL 20 was applied to the wrong interface and in the wrong direction.
Troubleshooting Standard IPv4 ACLs - Example 3
PC1 is unable to remotely access R1 using an SSH connection. Viewing the running configuration section for the VTY lines reveals that an ACL named PC1-SSH is correctly applied for inbound connections.
the process for correcting the error. Because the statement that needs to be corrected is the first statement, we use the sequence number 10 to delete it by entering no 10.