• Tag : mlag


MLAG Unicast Convergence

On a MLAG chassis, MAC addresses learned on individual peers are synced and appropriate interfaces are mapped to these 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, some loss of traffic may be observed. If a MLAG flaps on one peer, learned MAC addresses may have to be remapped to different interfaces such that the reachability is via the other peer in the MLAG domain. Until the remapping of MAC addresses and host routes complete, some amount of traffic may drop and...
Continue reading →

MLAG / Trunk Setting

Hoping to get some assistance on the below. Switch models: Arista 7050Qx-32S. We’re attempting to setup an MLAG between the two switches. The current issue we are facing, is that one switch respects the ‘switchport mode trunk’ command, while the other does not. Regardless of what is done, the second switch port group stays in ‘routed’, then when attempting to assign it to an MLAG ID, it states that it is required to be a trunk. We’re following: https://www.arista.com/en/um-eos/eos-section-13-4-configuring-mlag#ww1151451 Any help would be appreciated, it seems that no matter what we do it will not change from routed to trunk....
Continue reading →

MLAG inconsistent

Hello everybody, I’d like to have your opinion about this. I see that my MLAG are “inconsistent” (show mlag) and I get the following output when I run the command: “show mlag config-sanity”. Could you tell me what I have to check to solve this issue? Peer1: Global configuration inconsistencies: Feature Attribute Local value Peer value ————– ————— —————– ———- bridging 1 – True bridging 100 – True bridging 202 – True bridging 21 – True Peer2: Global configuration inconsistencies: Feature Attribute Local value Peer value ————– ————————— —————– ———- bridging mac-learning vlan 1 True – bridging mac-learning vlan 21...
Continue reading →

MLAG Config Heartbeat

Hello, I was wondering, what the recommended way is how to set up heartbeat between MLAG peers. At older EOS versions, such as in 4.19 I was able to separate Keep-alive traffic by running it via VRF Mgmt interface. This version did support the heartbeat entry under MLAG – see example below: leaf1(config-mlag)# peer-address heartbeat vrf mgmt dual-primary detection delay 10 action errdisable all-interfaces ! errdisable recovery cause mlagdualprimary In newer version, such as 4.23F, it seems that I am not allowed to run heartbeat via VRF Mmgmt anymore; this heartbeat entry is not available under MLAG config: leaf1(config-mlag)#peer-address...
Continue reading →

7800R3/7500R3/7280R3 MLAG support

Description EOS-4.23.1F added basic MLAG support for 7800R3, 7500R3 and 7280R3 platforms. The MLAG features that are currently supported are: Bridging Routing STP VARP L2 Multicast Starting in EOS-4.24.0F, the following feature is supported: Fast MLAG Unicast Convergence Platform compatibility DCS-7800R3 DCS-7500R3 DCS-7280R3 Configuration Refer to the MLAG basic configuration TOI document, as referenced below, for details on configuring a basic MLAG. Limitations The following limitations exist: Peer link must be configured as a LAG. Specifically, it cannot be a single front panel port. (BUG409958) Fast MLAG unicast convergence is not supported (BUG386201) starting in EOS-4.23.1F. In EOS-4.24.0F this limitation...
Continue reading →

EVPN – MLAG single homed hosts

Description As described in the Multi-VTEP MLAG TOI, singly connected hosts can lead to suboptimal peer-link utilisation. By adding a local VTEP to each MLAG peer, the control plane is able to advertise singly connected hosts as being directly behind a specific local VTEP / MLAG peer. The multi-VTEP MLAG feature has been extended to add EVPN control plane support. VXLAN bridging (EVPN Type-2 and Type-3 routes) and routing (EVPN Type-5 routes and IRB) are supported by this feature. When multi-VTEP MLAG mode is enabled, outgoing EVPN route advertisements will contain a nexthop and router MAC extended community as summarized...
Continue reading →

attached-host routes and MLAG

I have been experimenting in our test environment with attached-host routes on a vxlan network. We have are using asymmetric IRB across our vxlan infrastructure as it is (for the moment at least) simple enough for this not to cause us an issue. We want to use attached-host to ensure that the correct pair of leaf switches are used for routing “southbound” traffic. In the production environment there will be 5 pairs of leaf switches which will be routing traffic for the edge vlan. Behind this vlan are ~50 nodes that are connected with MLAG to the pairs of (7060CX)...
Continue reading →

“ip address virtual” support for PIM and IGMP

Description 4.22.1F introduces support for ip address virtual for PIM and IGMP in MLAG and Vxlan. On a VLAN, the same IP address can be configured using ip address virtual on both mlag devices as well as on different VTEPs. Control packets are source NATed by the kernel to a chosen IP address. The source NATing fails for PIM and IGMP. To overcome this, users can configure pim ipv4 local-interface and borrow the IP address to be used on the VLAN.  PIM and IGMP bypass the source NATing in the kernel. The interface configuration pim ipv4 local-interface allows PIM and...
Continue reading →

Default Load-balancing method in DCS-7160-48TC6-F

IN DCS-7160-48TC6-F version 4.20.7M EoS, we’re not able to check what default method is implemented in SW as we can do in other models like DCS-7280SR-48C6-F. In documentation, they’re not any reference to configuration like command line permit: #port-channel load-balance xp polynomial hash-a … Could you help me, please? Regards.

MLAG MaintenanceMode

Description The objective of Maintenance Mode on MLAG is to gracefully drain away the traffic (L2 and BGP) flowing through a switch that is part of the MLAG pair while the switch is put into maintenance and to gracefully add it back into the network and attract traffic again, once the switch is out of maintenance. Platform compatibility Compatible with all platforms. Configuration Maintenance Mode on a device in an MLAG Domain can only be configured for System Unit which consists of all the BGP neighbors and the interfaces. Following steps are putting device into maintenance mode: Setting mlag and non-mlag...
Continue reading →

MLAG Additional Port

Hi, I have existing MLAG between 2 switches in Arista 7050sx-64 and now I want to add additional Port to the MLAG for safety and redundancy there is any quick guide / commands for it? Regards,

MAC Address flapping – VXLAN with MLAG

As per the attached diagram, its a VXLAN EVPN setup. Everything was working fine on that side. Both switches in city A and City B have MLAG configured with the TOR Stack switches. After creating MLAG with the TOR Stack switches, all MAC addresses have started flapping. For example MAC address ab-bc-cd is coming from the server connected to TOR Stack switch in City B. On B-SW01 it is learning from Port-channel10 (MLAG) but on B-SW02 it is learning from VX1 interface (vxlan) which is coming from the RR via B-SW01 and then it hands it back to the TOR...
Continue reading →


Description In conventional VXLAN deployments, each MLAG pair of switches are represented as a common virtual VTEP. VXLAN traffic can be decapsulated on either switch. In some networks, there are hosts that are singly connected to one of the MLAG pair. VXLAN packets destined for the singly connected host could land on the other MLAG peer and subsequently be forwarded over the MLAG peer-link to reach the destination host. This path is undesirable since it would use up some bandwidth on the peer-link. Figure 1 : Suboptimal Packet Path to Singly Connected Host The Multi-VTEP MLAG feature prevents unicast VXLAN...
Continue reading →

MLAG+1Uplink router +ebgp

HI all let’s say we have a similar topology like the one above in which we have 2 arista switches forming a mlag peership between them and on the other side we just have 1 uplink router connected to both switches. is it possible to configure the router with a portchannel connected to both arista while running 2 different eBGP sessions one of each towards each arista? can this x2 eBGP sessions be runnig over the same vlan? let’s say svi1 on sw1, svi2 on sw2, svi3 on router port-channel sharing the same lan. If so, should that vlan be...
Continue reading →

MLAG Unicast Convergence

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...
Continue reading →

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...
Continue reading →

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


Get every new post on this blog delivered to your Inbox.

Join other followers: