How to debug IP on an access switch

HOME / How to debug IP on an access switch

Article Overview

Use the `debug ip packet` command with optional access-list filters to monitor IP traffic on a Cisco access switch safely.

Step-by-Step Approach

1. Verify Interface and IP Configuration Before debugging, ensure the interface is up and has the correct IP configuration:

show ip interface brief – checks interface status and IP assignment
show running-config – verifies IP addresses, VLANs, and routing settings 2. Use Debug Commands Carefully Debug commands provide real-time information but can consume CPU resources. Always:
Limit debug to specific interfaces or IPs using access-lists
Enable terminal monitoring if connected via SSH or console
Disable debug after troubleshooting with undebug all or no debug ip packet 3. Debug IP Packets The primary command for IP-level troubleshooting is:
debug ip packet [access-list-number] – shows all IP packets processed by the switch, filtered by an optional ACL to reduce output Example:

access-list 101 permit ip host 192.168.1.10 anydebug ip packet 101

This monitors only traffic from the host 192.168.1.10. 4. Monitor and Analyze Output

Look for dropped packets, routing issues, or ACL denials
Check source and destination IPs, protocol types, and interface information
Compare with show ip route and show arp to confirm expected paths 5. Additional Debugging Tools
ping and traceroute – verify connectivity and path
show logging – review system messages for errors
show mac address-table – confirm endpoint connectivity on the VLAN 6. Best Practices
Use debug during low-traffic periods or on test ports
Redirect output to a buffer or terminal monitor session
Avoid debug all in production as it can overload the switch By following these steps, you can safely debug IP issues on an access switch, identify misconfigurations, and verify packet flow without impacting network performance.

Solved: Debug access-list

I would like to debug and access list to see if it is catching traffic I want to pass. All I can find is a debig access

Troubleshoot DHCP Issues

Description of the Issue You do not get an IP address. Topology for the troubleshooting flow Refer to the following

Cisco Debug Command ⋆ | How to Use Cisco Debug Command?

Here, we have learned how to use Cisco Debug Command on Cisco routers and switches. Debugging is very important for network

Cisco Debug Commands – Overview & Safe Usage | debug ip packet,

By associating a debug command with an access list, the debug output is limited to only the packets or events that match the access

Cisco ME 3400E Ethernet Access Switch Debug Commands

Cisco ME 3400E Ethernet Access Switch Debug Commands Please confirm whether or not the This appendix describes the debug

Understanding Debugging with Access Control Lists

To check whether the packet is being received on the router or switch, first create extended acl with exact source and

Untitled Document []

If a communication session is closing when it should not be, an end-to-end connection problem can be the cause. The debug ip

Debugging on Cisco Access Points

Resolution: Follow the instructions in the Viewing Access Point Join Information section to see join statistics for the OfficeExtend

5. Debugging Access Lists

Chapter 5. Debugging Access ListsOnce you''ve formatted access lists and used them to implement policies, how do

5 techniques to debug network issues in Linux and Windows

5 techniques to debug network issues in Linux and Windows Debugging a network issue should start with basic

Debug IP Packet Detail Command on CISCO Router/Switch

Use This command enables detailed IP packet debugging messages. The debugging shows detailed IP information

debug ip packet – Real-Time Packet Tracing | CCNA Mastery | NetsTuts

Always try show ip route, show ip cef, and show access-lists before using debug. Cisco Embedded Packet Capture (EPC) is a safer

Debugging IP Packets on Cisco 9200 Switch

access-list 101 permit ip 192.168.50.0 0.0.0.255 192.168.60.0 0.0.0.255 ( removed Log here) access-list 101 permit ip

CCNA Troubleshooting Commands: The Complete Reference Guide

The MAC address table (CAM table) maps MAC addresses to the switch port where they were last seen. Use it to find

Cisco CLI Switch Command Cheat Sheet for 2025

A Cisco CLI switch command cheat sheet is therefore a valuable reference. It provides quick access to commonly

Catalyst 2960 Switch Debug Commands

Catalyst 2960 Switch Debug Commands This appendix describes the debug privileged EXEC commands that have been created or

Understand Important Information on Debug Commands

This document describes general guidelines on using debug commands including the debug ip packet command

Catalyst 3750 Command Reference, Release 12.2 (55)SE

Use the debug ip igmp max-groups privileged EXEC command to enable debugging of Internet Group Management Protocol (IGMP)

How to check or debug dhcp request and IP renew logs

There''re different commands to run: - debug ip packet details filtered with an acl - debug ip udp - debug ip dhcp

Solved: Debugging ping on Switch/Router

Hey, I was trying to debug some ping packets but I am having a diffucult time. I''ve been able to do this before but for

Catalyst 2960-S and 2960-C Switches Debug Commands

Catalyst Switch Debug Commands This appendix describes the debug privileged EXEC commands that have been created or

Debug Command on CISCO Router/Switch

Debug Command Debug Use This is a very useful but sometimes dangerous command. It allows you to see how the

Debug Named Access-List ACL

Hi everyone, Is there a way to debug named ACL? We have a named ACL in our environment for example: Extended

How To Access Your Network Switch

Introduction Introduction Accessing your network switch is essential for managing and configuring its settings.

Debug ip packet on Catalyst switch

I am using a cat 3550 or a 3750 and remove the fast switching on the vlan interface and when issuing the debug ip

Troubleshooting TCP/IP

The risks of using packet debugging may be compounded by the necessity of disabling fast switching for packet debugging to be

Solved: Debug an ACL

Hello, I''ve configured an ACL in a BVI interface an now is working as intended. But I would like to know which access

Debugging a Switch Router

Use debug commands to isolate problems, not to monitor normal network operation. Because the high overhead of debug

Understand the Ping and Traceroute Commands

This next code example shows the ping command after the debug ip packet detail command is enabled. Warning:

Cisco Debug Command Explained

This article describes how to use a debug command and its variations on a Cisco device. It also shows how to disable the debug

cheat-sheets/cheat-sheets/Aruba-HP-switches-debug-and-diagnostics

WARNING: I bring this command for completeness sake, but this command will run dozens/hundreds of debug commands, printing

Debugging IP traffic through a router switch module

Hi there, I have a remote Cisco 2811 router running IOS 12.3 (8r)T7 with an HWIC-D-9ESW Fast Ethernet switch

capturing traffic using ACL''s and debug

I am trying to capture traffic between two nodes on the network using an ACL (log) + a debug against that ACL but I

Cisco IOS Debug Command Reference

The debug ip access-list turboacl command is useful for debugging problems associated with turbo ACLs. Turbo

Debug messages

When a match occurs on an ACL "deny" ACE (with log configured), the switch sends an ACL message to configured debug

Identify Network Hardware IP Addresses on Local

Learn how to find fixed IP address of device on LAN for your network hardware, such as

DHCP IP debugging

I want to enable debugging on My Cisco Router, but what debugging do I enable? debug ip dhcp server packet - don''t

Aruba and HP switches debug and diagnostics commands cheat sheet

All commands were tested on HP/Aruba 5400 switches (specifically 5406Rzl2), but will work on any model with recent

How to debug IP on an access switch [PDF]