Posted on May 11, 2021 11:45 am
 |  Asked by michael
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i’m trying to setup mlag between two veos boxes but it won’t connect

when i run ‘show mlag’ the system-id shows as 00:00:00:00:00:00 on both boxes

i’ve seen a post to change this in ceos – does it need changed for veos mlag too?


Answered on May 11, 2021 11:46 am

Hi Michael,

Thanks for reaching out.

MLAG not forming between 2 vEOS boxes could be due to MTU configuration under interface vlan <VLAN associated with MLAG peer-link> in vEOS or it could be due to the system mac address generated by the type of Hypervisor(KVM,ESXI...,) on top of where vEOS boxes are deployed.

However before concluding we would like to review the tech-support log from both the MLAG peers to identify the issue.

Could you please provide us the output of "show tech-support | no-more" from both the MLAG devices and also could you please mention the Hypervisor on top of which vEOS boxes are running/deployed.




Posted by michael
Answered on May 11, 2021 10:10 pm


many thanks for your prompt reply, please see attached output as requested

the system is cisco cml2 and is hosted on an esxi host


Answered on May 20, 2021 8:53 am

Hi Michael,

Thanks for providing the tech-support logs.

Looks like the similar issue and workaround as that of cEOS MLAG.

As per the logs, the MLAG agent crashed with the below message. This is an issue with the system mac address:

------------- show agent logs crash -------------

===> /var/log/agents/Mlag-2394 Tue May 11 21:34:26 2021 <===
===== Output from /usr/bin/Mlag [] (PID=2394) started May 11 21:34:13.171815 ===
EntityManager::doBackoff waiting for remote sysdb version .........ok
2021-05-11 21:34:55.563308 2394 Log 0 %AGENT-6-INITIALIZED: Agent 'Mlag' initialized; pid=2394
Mlag: /src/Mlag/MlagAgentUtil.cpp:204: Arnet::EthAddr Mlag::msiAddr(Arnet::EthAddr): Assertion `( addr.word0() & 0x0200 ) == 0' failed.
Unix Time: 1620768975: Process 2394 lwp 2394 died with signal 6 (SIGABRT) code -6 (tkill)


As a workaround, please follow the below steps:

To override the default system-mac in vEOS:
Add the desired MAC address to the first line of the file /mnt/flash/system_mac_address, then reboot:

[admin@localhost ~]$ echo 1122.3344.5566 > /mnt/flash/system_mac_address

Mac address can be set to any random address something that does not match the OUI.

To override the default serial number or system-mac in vEOS:
>Create a file named 'veos-config' in /mnt/flash then add SYSTEMMACADDR=1122.3344.5566 and reboot.

Let us know if this helps




Posted by Franklin Davis
Answered on August 31, 2021 9:35 pm

Does this not work in newer vEOS images? I've tried both methods, but the system still retains the all-zeros system-id in the mLAG status:


spine-101#sh ver
Arista vEOS
Hardware version:
Serial number: 26344FB2EDC88B978D37B4C5DE172D45
Hardware MAC address: 1111.1111.1111
System MAC address: 1111.1111.1111

Software image version: 4.23.5M-cloud
Architecture: x86_64
Internal build version: 4.23.5M-cloud-18953532.4235M
Internal build ID: b3517920-4252-44c0-a04e-3448abeb6256

Uptime: 0 weeks, 0 days, 1 hours and 5 minutes
Total memory: 4008612 kB
Free memory: 1128608 kB

spine-101#sh mlag
MLAG Configuration:
domain-id : mlagspine
local-interface : Vlan4094
peer-address :
peer-link : Port-Channel10
peer-config :

MLAG Status:
state : Inactive
negotiation status : Connecting
peer-link status : Lowerlayerdown
local-int status : Lowerlayerdown
system-id : 00:00:00:00:00:00
dual-primary detection : Disabled
dual-primary interface errdisabled : False

MLAG Ports:
Disabled : 0
Configured : 0
Inactive : 0
Active-partial : 0
Active-full : 0

Posted by michael
Answered on August 31, 2021 9:56 pm


this works for me in 4.25 on cisco cml2

haven't tried it in eve-ng but will try and test it tomorrow

Posted by Tamas Plugor
Answered on August 31, 2021 10:41 pm

Hi Franklin,

Based on the above output, you are using cloudEOS, which is a cloud-based router only image, so no Layer2 features.

To use MLAG you will have to use vEOS-lab



Posted by Mathieu Millet
Answered on December 18, 2021 7:50 pm

For future folks,

The MAC addresses proposed don't work : please use 00 for the first byte. With the provided addresses, at reboot, the "physical" ethernet data interfaces in vEOS were set à 0000.0000.0000 :

Ethernet1 is down, line protocol is unknown (notconnect)
Hardware is Ethernet, address is 0000.0000.0000 (bia 5254.00d5.8b21)
IP MTU 9214 bytes (default)
Unconfigured, Unconfigured, auto negotiation: off, uni-link: n/a
Loopback Mode : None
0 link status changes since last clear
Last clearing of "show interface" counters never
5 minutes input rate 0 bps (- with framing overhead), 0 packets/sec
5 minutes output rate 0 bps (- with framing overhead), 0 packets/sec
0 packets input, 0 bytes
Received 0 broadcasts, 0 multicast
0 runts, 0 giants
0 input errors, 0 CRC, 0 alignment, 0 symbol, 0 input discards
0 PAUSE input
0 packets output, 0 bytes
Sent 0 broadcasts, 0 multicast
0 output errors, 0 collisions
0 late collision, 0 deferred, 0 output discards
0 PAUSE output

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