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Table of Contents Expand all

play_arrow Understanding Layer 2 Networking
- Layer 2 Networking
play_arrow Configuring MAC Addresses
- MAC Addresses
play_arrow Configuring MAC Learning
- MAC Learning
play_arrow Configuring MAC Accounting
- MAC Accounting
play_arrow Configuring MAC Notification
- MAC Notification
play_arrow Configuring MAC Table Aging
- MAC Table Aging
play_arrow Configuring Learning and Forwarding
- Layer 2 Forwarding Tables
play_arrow Configuring Bridging and VLANs
- Bridging and VLANs
play_arrow Configuring 802.1Q VLANs
- 802.1Q VLANs Overview
- 802.1Q VLAN IDs and Ethernet Interface Types
- Configuring Dynamic 802.1Q VLANs
- Enabling VLAN Tagging
- Configuring Tagged Interface with multiple tagged vlans and native vlan
- Sending Untagged Traffic Without VLAN ID to Remote End
- Configuring Tag Protocol IDs (TPIDs) on QFX Series Switches
- Configuring Flexible VLAN Tagging on PTX Series Packet Transport Routers
- Configuring an MPLS-Based VLAN CCC with Pop, Push, and Swap and Control Passthrough
- Binding VLAN IDs to Logical Interfaces
- Associating VLAN IDs to VLAN Demux Interfaces
- Configuring VLAN and Extended VLAN Encapsulation
- Configuring a Layer 2 VPN Routing Instance on a VLAN-Bundled Logical Interface
- Example: Configuring a Layer 2 VPN Routing Instance on a VLAN-Bundled Logical Interface
- Specifying the Interface Over Which VPN Traffic Travels to the CE Router
- Configuring Access Mode on a Logical Interface
- Configuring a Logical Interface for Trunk Mode
- Configuring the VLAN ID List for a Trunk Interface
- Configuring a Trunk Interface on a Bridge Network
- Configuring a VLAN-Bundled Logical Interface to Support a Layer 2 VPN Routing Instance
- Configuring a VLAN-Bundled Logical Interface to Support a Layer 2 VPN Routing Instance
- Configuring a Layer 2 Circuit on a VLAN-Bundled Logical Interface
- Example: Configuring a Layer 2 Circuit on a VLAN-Bundled Logical Interface
- Guidelines for Configuring VLAN ID List-Bundled Logical Interfaces That Connect CCCs
- Specifying the Interface to Handle Traffic for a CCC
- Specifying the Interface to Handle Traffic for a CCC Connected to the Layer 2 Circuit
play_arrow Configuring Static ARP Table Entries
- Static ARP Table Entries Overview
- Static ARP Entries on Ethernet Interfaces
- Configuring Static ARP Table Entries For Mapping IP Addresses to MAC Addresses
- Example: Configuring Static ARP Entries on Ethernet Interfaces
play_arrow Configuring Restricted and Unrestricted Proxy ARP
- Restricted and Unrestricted Proxy ARP Overview
- Configuring Restricted and Unrestricted Proxy ARP
play_arrow Configuring Gratuitous ARP
- Configuring Gratuitous ARP
play_arrow Adjusting the ARP Aging Timer
- Adjusting the ARP Aging Timer
play_arrow Configuring Tagged VLANs
- Configuring Tagged VLANs
play_arrow Stacking and Rewriting Gigabit Ethernet VLAN Tags
- Stacking and Rewriting Gigabit Ethernet VLAN Tags Overview
- Stacking and Rewriting Gigabit Ethernet VLAN Tags
- Configuring Frames with Particular TPIDs to Be Processed as Tagged Frames
- Configuring Tag Protocol IDs (TPIDs) on PTX Series Packet Transport Routers
- Configuring Stacked VLAN Tagging
- Configuring Dual VLAN Tags
- Configuring Inner and Outer TPIDs and VLAN IDs
- Stacking a VLAN Tag
- Stacking Two VLAN Tags
- Removing a VLAN Tag
- Removing the Outer and Inner VLAN Tags
- Removing the Outer VLAN Tag and Rewriting the Inner VLAN Tag
- Rewriting the VLAN Tag on Tagged Frames
- Rewriting a VLAN Tag on Untagged Frames
- Rewriting a VLAN Tag and Adding a New Tag
- Rewriting the Inner and Outer VLAN Tags
- Examples: Stacking and Rewriting Gigabit Ethernet IQ VLAN Tags
- Understanding Transparent Tag Operations and IEEE 802.1p Inheritance
- Understanding swap-by-poppush
- Configuring IEEE 802.1p Inheritance push and swap from the Transparent Tag
play_arrow Configuring Private VLANs
- Private VLANs
- Understanding Private VLANs
- Bridge Domains Setup in PVLANs on MX Series Routers
- Bridging Functions With PVLANs
- Flow of Frames on PVLAN Ports Overview
- Guidelines for Configuring PVLANs on MX Series Routers
- Configuring PVLANs on MX Series Routers in Enhanced LAN Mode
- Example: Configuring PVLANs with Secondary VLAN Trunk Ports and Promiscuous Access Ports on a QFX Series Switch
- IRB Interfaces in Private VLANs on MX Series Routers
- Guidelines for Configuring IRB Interfaces in PVLANs on MX Series Routers
- Forwarding of Packets Using IRB Interfaces in PVLANs
- Configuring IRB Interfaces in PVLAN Bridge Domains on MX Series Routers in Enhanced LAN Mode
- Example: Configuring an IRB Interface in a Private VLAN on a Single MX Series Router
play_arrow Configuring Layer 2 Bridging Interfaces
- Layer 2 Bridging Interfaces Overview
- Configuring Layer 2 Bridging Interfaces
- Example: Configuring the MAC Address of an IRB Interface
play_arrow Configuring Layer 2 Virtual Switch Instances
- Layer 2 Virtual Switch Instances
play_arrow Configuring Link Layer Discovery Protocol
- LLDP Overview
- Configuring LLDP
- Example: Configuring LLDP
- Configuring the Transmission of Maximum VLAN Name TLVs in LLDP
- LLDP Operational Mode Commands
- Tracing LLDP Operations
play_arrow Configuring Layer 2 Protocol Tunneling
- Layer 2 Protocol Tunneling (L2PT)
play_arrow Configuring Virtual Routing Instances
- Virtual Routing Instances
play_arrow Configuring Layer 3 Logical Interfaces
- Layer 3 Logical Interfaces
play_arrow Configuring Routed VLAN Interfaces
- Routed VLAN Interfaces
play_arrow Configuring Integrated Routing and Bridging
- Integrated Routing and Bridging
play_arrow Configuring VLANS and VPLS Routing Instances
- VLANs and VPLS Routing Instances
play_arrow Configuring Multiple VLAN Registration Protocol (MVRP)
- Multiple VLAN Registration Protocol
play_arrow Configuring Ethernet Ring Protection Switching
- Example: Configuring Ethernet Ring Protection Switching on EX Series Switches
- Example: Configuring Ethernet Ring Protection Switching on QFX Series and EX Series Switches Supporting ELS
play_arrow Configuring Q-in-Q Tunneling and VLAN Translation
- Configuring Q-in-Q Tunneling and VLAN Q-in-Q Tunneling and VLAN Translation
play_arrow Configuring Redundant Trunk Groups
- Redundant Trunk Groups
- Q-in-Q Support on Redundant Trunk Links Using LAGs with Link Protection
play_arrow Configuring Proxy ARP
- Proxy ARP
play_arrow Configuring Layer 2 Interfaces on Security Devices
- Layer 2 Interfaces on Security Devices
play_arrow Configuring Security Zones and Security Policies on Security Devices
- Security Zones and Security Policies on Security Devices
play_arrow Configuring Ethernet Port Switching Modes on Security Devices
- Ethernet Port Switching Modes on Security Devices
play_arrow Configuring Ethernet Port VLANs in Switching Mode on Security Devices
- Ethernet Port VLANs in Switching Mode on Security Devices
play_arrow Configuring Secure Wire on Security Devices
- Secure Wire on Security Devices
play_arrow Configuring Reflective Relay on Switches
- Reflective Relay on Switches
play_arrow Configuring Edge Virtual Bridging
- Edge Virtual Bridging
play_arrow Troubleshooting Ethernet Switching
- Troubleshooting Ethernet Switching
- Troubleshooting Ethernet Switching on EX Series Switches
play_arrow Configuration Statements and Operational Commands
- Junos CLI Reference Overview

list Table of Contents

English

ON THIS PAGE

Problem
Solution

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Troubleshooting Ethernet Switching

date_range 20-Dec-24

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Problem

Description

Sometimes a MAC address entry in the switch’s Ethernet switching table is not updated after the device with that MAC address has been moved from one interface to another on the switch. Typically, the switch does not wait for a MAC address expiration when a MAC move operation occurs. As soon as the switch detects the MAC address on the new interface, it immediately updates the table. Many network devices send a gratuitous ARP packet when switching an IP address from one device to another. The switch updates its ARP cache table after receipt of such gratuitous ARP messages, and then it also updates its Ethernet switching table.

Sometimes silent devices, such as syslog servers or SNMP trap receivers that receive UDP traffic but do not return acknowledgment (ACK) messages to the traffic source, fail to send gratuitous ARP packets when a device moves. If such a move occurs when the system administrator is not available to explicitly clear the affected interfaces by issuing the clear ethernet-switching table command, the entry for the moved device in the Ethernet switching table is not updated.

Solution

Set up the switch to handle unattended MAC address switchovers.

Reduce the system-wide ARP aging timer. (By default, the ARP aging timer is set at 20 minutes. The range of the ARP aging timer is from 1 through 240 minutes.)
```
[edit system arp]
user@switch# set aging-timer 3
```
Set the MAC aging timer to the same value as the ARP timer. (By default, the MAC aging timer is set to 300 seconds. The range is 60 to 1,000,000 seconds.)
```
[edit protocols l2-learning]
user@switch# set global-mac-table-aging-time 180
```

The ARP entry and the MAC address entry for the moved device expire within the times specified by the aging timer values. After the entries expire, the switch sends a new ARP message to the IP address of the device. The device responds to the ARP message, thereby refreshing the entries in the switch’s ARP cache table and Ethernet switching table.

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