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	==Introduction==		==Introduction==

Admin: Created page with "Category:Wiki ==Introduction== MLAG (Multi-Chassis Link Aggregation) is a network feature that allows two physical switches (MLAG peers) to present themselves as a single logical switch to the connected devices. This provides high availability, increased bandwidth, and redundancy without requiring a single switch to be a point of failure. Arista EOS supports MLAG, enabling the creation of a redundant, active-active link aggregation configuration. This guide covers..."

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Created page with "Category:Wiki ==Introduction== MLAG (Multi-Chassis Link Aggregation) is a network feature that allows two physical switches (MLAG peers) to present themselves as a single logical switch to the connected devices. This provides high availability, increased bandwidth, and redundancy without requiring a single switch to be a point of failure. Arista EOS supports MLAG, enabling the creation of a redundant, active-active link aggregation configuration. This guide covers..."

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==Introduction==
MLAG (Multi-Chassis Link Aggregation) is a network feature that allows two physical switches (MLAG peers) to present themselves as a single logical switch to the connected devices. This provides high availability, increased bandwidth, and redundancy without requiring a single switch to be a point of failure. Arista EOS supports MLAG, enabling the creation of a redundant, active-active link aggregation configuration.

This guide covers the essential commands and configuration steps for MLAG on Arista EOS.

==MLAG Overview==
In an MLAG setup, two switches act as MLAG peers and share a single logical control plane for link aggregation. The MLAG peer switches maintain synchronization and communicate through a dedicated MLAG interconnect link, allowing traffic to flow seamlessly between them. MLAG supports Layer 2 and Layer 3 connectivity.

### Key Features of MLAG:
* **Active-Active Links**: Provides load balancing and redundancy by using multiple links between switches and end devices.
* **Redundancy**: If one switch fails, the other switch in the MLAG pair can continue to forward traffic.
* **No Single Point of Failure**: MLAG avoids the single point of failure in traditional link aggregation setups.
* **Simplified Network Design**: MLAG allows for the use of standard LACP (Link Aggregation Control Protocol) to create logical links between devices.

==Basic MLAG Configuration==
To configure MLAG, you need to set up the MLAG peer, the MLAG domain, and the MLAG interconnect link. Here are the steps to configure MLAG on Arista EOS.

### Step 1: Enable MLAG on Both Switches
* '''mlag config-id <number>'''
- Configures the MLAG configuration ID (domain). This ID must be the same on both switches in the MLAG pair.

* '''mlag peer-address <IP-address>'''
- Configures the IP address of the MLAG peer. This IP address is used for communication between the MLAG peers.

* '''mlag peer-link <interface-name>'''
- Configures the interconnect link between the two MLAG peers. This interface must be a high-speed link between the peers, often configured as a trunk or a port-channel.

* '''mlag local-interface <interface-name>'''
- Configures the local interface for the MLAG instance. This interface is used for communication with the peer.

### Step 2: Configure the MLAG Peer Link
The peer link connects the two switches and allows them to communicate. It typically connects the two switches via a high-speed link like a 10/40/100Gb Ethernet link.

* '''interface Ethernet <slot>/<port>'''
- Configures the peer link interface.

* '''switchport mode trunk'''
- Configures the peer link interface as a trunk port to allow multiple VLANs.

* '''channel-group <group-id> mode active'''
- Configures the peer link as part of a port channel and sets the link aggregation mode to "active."

### Step 3: Configure the MLAG Interface
The MLAG interface is the logical interface that both switches share to appear as a single logical switch to the connected devices.

* '''interface Vlan <vlan-id>'''
- Creates the MLAG VLAN interface.

* '''mlag <vlan-id>'''
- Assigns the VLAN to the MLAG instance.

* '''ip address <IP-address> <subnet-mask>'''
- Configures the IP address on the MLAG interface.

* '''no shutdown'''
- Brings the MLAG interface up.

### Step 4: Configure Port-Channels on Each Switch
Port-channels are used to bundle multiple physical links into a single logical link. These port-channels are associated with the MLAG configuration.

* '''interface Ethernet <slot>/<port>'''
- Configures each physical interface that will be added to the port-channel.

* '''channel-group <group-id> mode active'''
- Configures the physical interface as part of the port-channel in active mode.

* '''interface Port-Channel <group-id>'''
- Configures the port-channel interface.

* '''switchport mode trunk'''
- Configures the port-channel as a trunk to carry multiple VLANs.

* '''mlag <vlan-id>'''
- Assigns the port-channel to the MLAG instance.

### Step 5: Enable MLAG on Both Switches
Ensure that both switches in the MLAG pair are configured with identical settings.

* '''show mlag'''
- Displays the status of MLAG on the device, including the peer status and configured VLANs.

* '''show mlag peer-link'''
- Displays the status of the MLAG peer link.

* '''show mlag interface'''
- Displays the status of MLAG interfaces.

==MLAG Troubleshooting==
Here are some useful troubleshooting commands to check MLAG status and resolve any issues.

* '''show mlag'''
- Displays the MLAG configuration and operational status. It shows the local MLAG configuration, peer status, and MLAG interfaces.

* '''show mlag peer-link'''
- Displays the status of the peer link between MLAG switches. This command provides information about the health and status of the peer link.

* '''show mlag interface'''
- Displays detailed information about MLAG interfaces, including whether they are operational or in a failed state.

* '''show mlag summary'''
- Displays a summary of the MLAG configuration, including peer switch information and interface status.

* '''show interfaces ethernet <slot>/<port>'''
- Displays the status of a specific interface, including any errors or issues.

* '''show spanning-tree vlan <vlan-id>'''
- Displays the spanning tree protocol (STP) status for a specific VLAN. STP is crucial in an MLAG configuration to ensure loop-free operation.

* '''show logging'''
- Displays system logs, including any relevant information about MLAG or peer link issues.

* '''debug mlag'''
- Enables debugging of MLAG operations to help troubleshoot problems.

* '''clear mlag statistics'''
- Clears the MLAG statistics counters, which can be useful after resolving issues or performing maintenance.

==MLAG Redundancy and Failover==
MLAG provides high availability by ensuring that both switches in the MLAG pair can forward traffic simultaneously. If one switch fails, the other will continue forwarding traffic with minimal disruption.

### MLAG Failover Behavior:
* If a port-channel member goes down on one switch, the traffic is automatically forwarded via the other switch in the MLAG pair.
* If the MLAG peer link fails, the switch will attempt to maintain communication with its peer through the local MLAG interface.
* If the MLAG peer switch fails completely, the local switch can still forward traffic for MLAG-configured VLANs via the local interfaces.

### Configuring Redundancy:
* Ensure both switches are connected to each other via a high-speed, redundant peer link.
* Utilize spanning-tree protocol (STP) to ensure no loops are present in the network. STP configuration should be consistent across both MLAG peers.

* '''show spanning-tree'''
- Displays the spanning-tree topology, which should have no loops, especially in an MLAG configuration.

==Advanced MLAG Configuration==
Arista EOS provides additional advanced features for MLAG configurations, such as MLAG over multiple interfaces, VLANs with specific MLAG configurations, and integrating MLAG with other protocols like EVPN.

### MLAG with EVPN:
* EVPN (Ethernet VPN) can be used as a control plane to manage MLAG configurations in larger networks. By using EVPN, you can achieve more flexible and scalable MLAG deployment with better fault tolerance.

### MLAG on Virtual Router Redundancy Protocol (VRRP):
* MLAG can also be configured to work with VRRP to provide high availability for Layer 3 gateways.

==MLAG Security Best Practices==
* Ensure that MLAG peer links are physically secured to prevent unauthorized access.
* Use network access control lists (ACLs) to limit the devices that can connect to the MLAG pair.
* Regularly monitor the status of MLAG and peer links using `show mlag` and other relevant commands.
* Use authentication and encryption methods (such as IPsec or MACsec) for MLAG interconnect links to protect against eavesdropping or tampering.

ARISTA - MLAG - Revision history

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