Posted on January 29, 2018 9:45 am
 |  Asked by Hitoshi Onozaki
 |  687 views
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Hi,

I am a beginner of Arista switch. I have two questions on that.

<Information of the switch>
model:Arista DCS-7150S-64-CL
version:EOS-4.15.7M

1) The flood-list and the mac address  learning disappears when the switch restarts. Why?

I set the infomation that “HER flood-list and mac address learning” on the Arista switch that using the OVSDB management.

Example of setting  is as follows.(The following command executed on CVX.)
-bash-4.1# vtep-ctl add-mcast-remote <LS-name> unknown-dst vxlan_over_ipv4 <vtep-ip>
-bash-4.1# vtep-ctl add-ucast-remote  <LS-name>  <MAC-address> vxlan_over_ipv4 <vtep-ip>

One day, I stopped the Arista switch and started it.
Then, the information(HER flood-list and mac address  learning) disappeared from Arista switch…
Note:
 I confirmed it by executing the following command on Arista Switch.
 # show mac address-table
 # show vxlan flood vtep

Not only the mac address  learning but also the flood-list disappeared.
Is this the expected behavior?

2) How to recover flood-list and mac address learning.

In the above case,
For recovery, I reconfigure by using the OVSDB management.

Example of setting  is as follows.
-bash-4.1# vtep-ctl add-mcast-remote <LS-name> unknown-dst vxlan_over_ipv4 <vtep-ip>
-bash-4.1# …
-bash-4.1# …(Repeat for the number of vtep.)
-bash-4.1# vtep-ctl add-ucast-remote  <LS-name>  <MAC-address> vxlan_over_ipv4 <vtep-ip>
-bash-4.1# …
-bash-4.1# …(Repeat for the number of VM.)

It is very redundant and takes time…
Is there any good method for this situation?
(For example, resynchronization by eAPI of information on OVSDB (is Possible?) etc…)

Thanks,

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Posted by Alexis Dacquay
Answered on August 17, 2020 12:00 pm

Hi,

1) Understanding the symptoms

Yes it is normal.

Can you provide your configuration to understand what flood-list and MAC address learning method you are using?
By "disappear", do you mean from the EOS configuration, or from the hardware tables, or the control-plane tables?

The only information that is persistent over a reload is the configuration file itself. The dynamic learning would be reinitialised upon reboot, like a restart from start, literally. So whatever was learn dynamically or from a 3rd party controller would have been flushed as well, and would need to be re-learnt.

If the Flood-list is statically configured in CLI, then it would remain.
If it was dynamically learnt from EVPN or NSX, then it would need to be re-learnt, but NSX via CVX should push it again. Is it not the case?

The MAC address table is always dynamic (except statically configured entry via the EOS CLI)

OVSDB is supposed to be pushing the relevant information. Rather than typing commands by hand one by one for each VTEP and VM, the expectation is that a controller would do that automatically as part of the OVSDB-to-EOS communications.
Can you clarify whether you run NSX or what exact form of OVSDB sender you are using, since you seem to get involved in lot of manual CLI commands?

2) Alternative

If you want something persistent (NSX / OBSDB is supposed to be dynamic), then you can configure static configs, either:
- configure the EOS CLI with API (recommended for what I understand so far from your use case, generates static configs on the switch, but dynamically called, added/removed.)
- Configure the EOS CLI manually (static)

Intro to eAPI:
https://eos.arista.com/arista-eapi-101/

Example of programming VLAN and VXLAN with eAPI (maybe you can reusing as-is?)
https://eos.arista.com/script-example-automating-vxlan-deployments-with-eapi/

Regards,
Alexis

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