• Tag : mlag


MLAG Unicast Convergence

Feature Update: Please note that this feature has been updated and enhanced in EOS-4.24.1F MLAG Unicast Convergence provides the ability to fast redirect traffic through the other peer, in the event of local peer reloading or local peer’s MLAG interface(s) flapping. As of release 4.20.5F, this feature is now available on 7160 series switches. Here is a link to earlier TOI on Mlag Unicast Convergence: https://eos.arista.com/eos-4-18-0f/mlag-unicast-convergence/

MLAG Dual Primary Detection

When MLAG peer-link goes down, the secondary peer assumes the primary peer is down/dead, and takes over the primary role. It is possible that when peer-link is down, the primary isn’t actually down/dead and both MLAG peers think they are the primary. This is called “dual-primary” condition/state. In this state, each peer will run Layer-2 protocols such as Spanning Tree Protocol independently. Depending on the topology, this can cause loops in the network. This can also impact IGMP snooping feature. The Dual Primary Detection feature uses the management interface as an out-of-band connection between the two peers along with the peer-link. Once configured, the MLAG peers will send...
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MLAG: Traffic flow for single-homed hosts

Objective The objective of this document is to explain the traffic flows, best practice designs, and configuration details when single-homed devices are connected to an MLAG domain.  It is assumed that the reader is familiar with the concept of Leaf-Spine fabrics, MLAG, and VXLAN. More details about these concepts can be found on EOS Central. Recommended articles are: MLAG – Basic configurationMLAG – Advanced configurationVXLAN bridging with MLAGVXLAN routing with MLAG Introduction Arista’s Multi-Chassis LAG (MLAG) technology provides the ability to build a loop-free active-active layer 2 topology. The technology operates by allowing two physical Arista switches to appear as...
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MLAG ECMP load balance method

Hello, I need a help with proper design. I have a pair 7050X with MLAG configuration. To the downstream devices I have 2 mlag port-channels each contain 2 links. 7050X will provide L3 functionality : gateways and routing.  I would like to enabling ecmp and load-balance the traffic. What will be the best method to choose in this scenario ?   Thank you

OSPF on MLAG Peers

I have a simple single area OSPF topology with two routers. The setup exchanges routes just fine. I would like to convert one of the router/switches to a MLAG configuration. My question is what would be the correct way to approach adding the peer system into the OSPF configuration? Do I treat the two MLAG peered systems as discreet as far as OSPF is concerned? Does/can VARP play a role? I would guess not since the routing engines are separate. Thanks

vEOS – Logical VTEP with MLAG – VXLAN interpreted on MLAG Peer

Hello all, Please see attached picture for network topolgy. I try to use VXLAN with HER for DCI, together with BGP&BFD as routing protocol (for underlay) between Site A and Site B.– Site A: VLAN100 mapped to DCI VNI 10100– Site B: VLAN1100 mapped to DCI VNI 10100– spine1&spine2 as mlag peers with logical VTEP– spine3 as single VTEP– ports for DCI configured as L3 routed (no switchport)– EBGP between spine1 and spine3 as well as spine2 and spine3– VLAN4093 between spine1 ( and spine2 ( for re-routing in case one DCI is down– IBGP between spine1 and spine2– target...
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MLAG Unicast Convergence

Feature Update: Please note that this feature has been updated and enhanced in EOS-4.24.1F On an MLAG chassis we sync the MAC addresses learnt on individual peers and make sure we use the appropriate interface to map the MAC addresses. In case of unexpected events like reloading of one of the peers in the MLAG chassis or flapping of one or more MLAG interfaces, we may observe some loss of traffic. If an MLAG flaps on one peer, then we may have to remap the MAC addresses learned, such that the reachability is via the other peer in the MLAG...
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DHCP Snooping and MLAG interfaces

I have a vlan that I want to allocate IP addresses to the hosts based on their switch port-number so that the machines will get a consistent IP address based on their physical location in our cluster. The interface that this vlan is presented to the host is running as an MLAG. The Circuit ID gets correctly inserted as switchname:PortChannelxxx but which switchname will be sent is not clear. Any advice on how to make this configuration work reliably (we can only have one circuit ID in the DHCP configuration)? Should I only run dhcp snooping on one of the...
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VXLan, MLAG and duplicate ARP

We having an issue that we believe is related to receiving duplicate ARP requests. We’ve got nodes (part of openstack) connected to a pair of 7060 switches using MLAG, these 7060 switches then join a VXLan to connect to other pairs of 7060 switches where other nodes exist. The behaviour we’re seeing with ARP requests is that the broadcast is being flooded to the VTEP that is on both switches in the MLAG group, this is then being forwarded down both legs to the node, so the node sees the request twice. This seems to be confusing the OVS running...
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MSTP and MLAG Best Pratices

Hello folks, Following situation:– 2 datacenters– 2 spines per datacenter (short name: S1 & S2 in DC1, S3 & S4 in DC2)– multiple leafs per datacenter connected to both spines via bowtie MLAG– S1 & S2 forms MLAG pair, S3 & S4 forms MLAG pair– CWDM: S1 connected to S3, S2 connected to S4 (ring)– bowtie MLAG between MLAG pairs S1/S2 and S3/S4– MSTP with 1 MST instance What is the best practise for configuring MSTP root bridges?Configuring S1 as primary and S2-4 as secondary? Or S1 AND S2 as primary and S3+S4 as secondary?As far as I know, in...
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Hi; Can you have MLAG without Stateful Switch Over What exactly the advantage of MLAG with SSO VS MLAG without SSO? For SSO to be functional, do you need to have the exact software image on both peers?

A comparison of virtual ip commands

The ‘ip virtual-router’ command Switch1:   Switch1(config)#interface vlan 10   Switch1(config-if-Vl10)#ip address   Switch1(config-if-Vl10)#ip virtual-router address   Switch1(config)#ip virtual-router mac-address 00:1c:73:00:00:99 Switch2:   Switch2(config)#interface vlan 10   Switch2(config-if-Vl10)#ip address   Switch2(config-if-Vl10)#ip virtual-router address   Switch2(config)#ip virtual-router mac-address 00:1c:73:00:00:99 The ‘ip virtual-router address’ command requires an IP address to be configured on the SVI where it is applied. How does the host resolve ARP for the default gateway/vIP? Gratuitous ARPs: Gratuitous ARPs are periodically sent from both switches which have VARP configured. In the gratuitous ARPs the configured vMAC is used as the Ethernet Source MAC. The ARP message  informs the host that Virtual IP...
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VARP – IP router not configured with MLAG peer MAC address

Hi forum, I have configured VARP on four 7050QX with 4.16.6M using the following config: <pre>ip virtual-router mac-address 00:1c:73:00:00:99 interface vlan 999 ip address ip virtual-router address</pre> The virtual IP is pingable, but what does “IP router is not configured with Mlag peer MAC address” means in the output below? <pre>spine1(config)#sh ip virtual-router IP virtual router is configured with MAC address: 001c.7300.0099 IP router is not configured with Mlag peer MAC address MAC address advertisement interval: 30 seconds Protocol: U – Up, D – Down, T – Testing, UN – Unknown NP – Not Present, LLD – Lower...
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MLAG heartbeat timeout enhancement

In an MLAG setup, periodic TCP/UDP heartbeats are sent over peer-link to ensure IP connectivity between peers. Prior to EOS-4.17.0F release, a heartbeat timeout on MLAG primary/secondary causes MLAG state to become inactive and leads to spanning-tree topology changes, LACP port-channel link-flaps etc. From EOS-4.17.0F onwards, a heartbeat timeout on MLAG primary/secondary doesn’t cause MLAG state change, instead MLAG will remain in same state and also remain active. Status CLI command “show mlag detail” captures statistics related to heartbeat timeout events. Configured heartbeat interval : 4000 ms Effective heartbeat interval : 4000 ms Heartbeat timeout : 60000 ms Last heartbeat...
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Overview MLAG ISSU (In-Service Software Upgrade) upgrades EOS software on one MLAG peer with minimal traffic disruptions on active MLAG interfaces and without changing the network topology. Note: Traffic impact could be seen for orphan links, active partial links and packets in flight MLAG considerations before upgrade I. Check for configuration inconsistencies Following features should be configured consistently on each switch: VLANs Switchport configuration on port channel interfaces that are configured with an MLAG ID STP configuration (global) In EOS versions 4.15.2F onwards, we can use MLAG configuration check feature: https://eos.arista.com/eos-4-15-2f/mlag-config-check/ II. Resolve ISSU warnings Resolve the following warnings before...
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MLAG – unique domain ID and IP-pair needed for each leaf pair?

Hello I am currently testing the L2/MLAG-Design in GNS3 using vEOS. My topology consists of 2 spine switches and 3 pairs of leaf switches (=6 leaf switches).The 2 spine-switches will form an MLAG peering, as well as each of the leaf switch pairs. Each leaf is connected to both spines –> bowtie MLAG. Now my questions: 1. If I have multiple leaf pairs, can I use the same MLAG domain-ID for each leaf pair, or should I use a distinct one for each pair? 2. Is there any reason I should not use the same 2 IPs for MLAG peering...
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MLAG ToR pair to switches in U-shape

Hi Guys, Just want check how to configure Arista EOS to support the following ToR1 —-ToR2 |               | SW1 —- SW2 ToR1 & ToR2 are Arista MLAG pair to appear as single logical switch SW1 & SW2 is access sw running STP protocol Rgds Art  


Hi all, I just wanted to know how does Stp works in MLAG. Anyone document would really help me.

VXLAN Routing with MLAG

Introduction This document describes the operation and configuration of  VXLAN routing on an Arista platform in conjunction with MLAG for redundancy. The configuration and guidance within the document unless specifically noted is based on the platforms and EOS releases noted in the table below. Arista’s Multi-Chassis LAG (MLAG) technology provides the ability to build a loop free active-active layer 2 topology. The technology operates by allowing two physical Arista switches to appear as a single logical switch (MLAG domain), third-party switches, servers or neighbouring Arista switches connect to the logical switch via a standard port-channel (static, passive or active) with...
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