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How to mirror core switches

Port mirroring on core switches allows you to copy traffic from one or more source ports to a designated destination port for monitoring and analysis.Understanding Port Mirroring

Port mirroring, also called SPAN (Switched Port Analyzer) on Cisco devices, is a technique that replicates network traffic from source ports or VLANs to a destination port where a monitoring device, such as a network analyzer or intrusion detection system, is connected . It supports:

  • Ingress mirroring: Copies incoming traffic to the destination port.
  • Egress mirroring: Copies outgoing traffic to the destination port.
  • Local mirroring: Source and destination ports are on the same switch.
  • Remote mirroring: Source and destination ports are on different switches, often using a remote session .
Steps to Configure Port Mirroring on Core Switches
  1. Verify Capabilities: Ensure your core switch supports port mirroring and check the maximum number of sessions and destination ports .
  2. Identify Source Ports or VLANs: Determine which ports or VLANs you want to monitor. Core switches often handle multiple VLANs, so you may need classifier-based policies to select specific traffic .
  3. Select Destination Port: Choose a port where the monitoring device will be connected. Note that this port cannot be used for normal network traffic while mirroring is active .
  4. Configure the Mirroring Session:
    • On Cisco switches, for example:

      monitor session 1 source interface gigabitEthernet1/1/1monitor session 1 destination interface gigabitEthernet1/1/2 This sets up session 1 to mirror traffic from the source port to the destination port .

    • On Aruba or Extreme Networks switches, you may configure local or remote mirroring sessions and apply classifier-based policies to filter traffic by VLAN, IP, or protocol .
  5. Apply Filters (Optional): For large core switches, you can filter mirrored traffic by protocol, IP address, or VLAN to reduce the volume sent to the monitoring device .
  6. Verify Configuration: Use commands to display active mirroring sessions and ensure traffic is being mirrored correctly. For Cisco, show monitor session displays session details .
Best Practices
  • Avoid Mirroring All Traffic: Mirroring all ports on a core switch can overwhelm the monitoring device and impact switch performance.
  • Use Remote Mirroring for Distributed Networks: If monitoring traffic from multiple switches, configure remote mirroring endpoints to centralize traffic collection .
  • Monitor Both Ingress and Egress if Needed: Some troubleshooting scenarios require observing both incoming and outgoing traffic .
  • Document Sessions: Keep track of session numbers and destination ports to prevent conflicts, especially in multi-switch environments . By following these steps, you can effectively mirror traffic on core switches for network analysis, security monitoring, and troubleshooting without disrupting normal operations.
How to mirror core switches

Mirroring configuration examples

For this mirroring configuration, the administrator configures a mirroring destination (with a remote exit port of B10) on switch C, and

Configuring Port Mirroring

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SPAN Session or Port Mirroring

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Port Mirroring

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Aruba Switch Port Mirroring

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Mirroring configuration examples

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Use RSPAN to mirror traffic from remote switches

Remote Switched Port Analyzer (RSPAN) allows you to mirror traffic from remote switches for analysis on a local destination port.

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SPAN Session or Port Mirroring

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Port Mirroring

Port mirroring causes the switch to make a copy of a traffic flow and send the copy to a device for analysis. Use port mirroring in

How to configure port mirroring in L2 switch..

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Replacing core switch question? We are replacing our existing catalyst 4510R switch with 6 meraki ms250-48p switches. Currently

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Now I would like to setup another new switch so that the traffic on the new switches can be also mirrored and send to

Configuring local mirroring

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Solved: Replace Core Switch

Hi I am wondering how most people go about this. If I was replacing a core switch, how would you guys recommend I

Configuring Traffic Mirroring

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Solved: Port Mirroring on MS Switches

Hi, I have a client that wants to collect internal data on a internal switch stack and mirror that to an security appliance

Mirroring configuration examples

For this mirroring configuration, the administrator configures a mirroring destination (with a remote exit port of B10) on switch C, and

Configuring Port Mirroring

To configure port mirroring on a device, perform this procedure. Enables privileged EXEC mode. Enter your password, if prompted.

Port Mirroring: What It Is, How It Works, and Why It''s

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Configuring Traffic Mirroring

•Layer 2 or Layer 3 traffic mirroring:BothLayer2andLayer3sourceportscanbemirrored. •ACL-based traffic

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If yes then we can configure RSPAN on Cisco switches and extend the vlan till ESXi virtual switch and from there we

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We have created a Mirror (Span) port on our Core switch in order to see all traffic on the network, however, we are

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Extreme Networks Port Mirroring (Spanning) for Packet Capturing

In this example we''ll be mirroring port 1 to port 10, ergo, port 1 will have the device whose traffic we want to capture

Cisco Tech Talk: Switch Port Mirroring Example

In this Cisco Tech Talk, we''ll show you how to configure port mirroring on a CBS 250 or 350 series switch through the

Mirroring configuration examples

For this mirroring configuration, the administrator configures a mirroring destination (with a remote exit port of B10) on switch C, and

Configuring Port Mirroring

To configure port mirroring on a device, perform this procedure. Enables privileged EXEC mode. Enter your password, if prompted.

Port Mirroring: What It Is, How It Works, and Why It''s

Discover what port mirroring is, how it works, and how to

Configuring Traffic Mirroring

•Layer 2 or Layer 3 traffic mirroring:BothLayer2andLayer3sourceportscanbemirrored. •ACL-based traffic

how to configure SPAN port scenario

If yes then we can configure RSPAN on Cisco switches and extend the vlan till ESXi virtual switch and from there we

Mirror Port on Core Switch not seeing other traffic from edge switches

We have created a Mirror (Span) port on our Core switch in order to see all traffic on the network, however, we are

Switch Port Mirroring Explained: What is Mirror Port in Switch?

Learn what mirror port in switch means and how ethernet switch port mirroring works. Explore types of port mirroring,

Extreme Networks Port Mirroring (Spanning) for Packet Capturing

In this example we''ll be mirroring port 1 to port 10, ergo, port 1 will have the device whose traffic we want to capture

Cisco Tech Talk: Switch Port Mirroring Example

In this Cisco Tech Talk, we''ll show you how to configure port mirroring on a CBS 250 or 350 series switch through the

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