From time to time, in Cumulus Linux it is necessary to statically set a MAC address for a configuration item.
Why not Pick a Random MAC Address?
When configuring arbitrary static MAC addresses, there are several considerations. Picking a random MAC address can lead to problems that are potentially very difficult to troubleshoot. This article is not intended to be comprehensive in that regard, rather it just highlights the issue and directs you toward a safer way of allocating static MAC addresses.
First, it is important that the static MAC addresses do not conflict with any other device on a given L2 segment, unless otherwise required. For example, while the MAC address used for a chassis ID on an MLAG pair must match, you cannot use that same MAC address on another MLAG pair.
Further, avoiding multicast MAC addresses for manually configured MAC addresses is usually required. Depending on where you are applying the static MAC address, that can could lead to to some unwanted behavior.
Reserved MAC Address Ranges
For this purpose, Cumulus Networks has reserved portions of the OUI MAC address range specifically for MLAG and VRR. So if you are configuring MLAG or VRR on devices running licensed versions of Cumulus Linux, we recommend you use the following ranges for those statically configured MAC addresses.
|VRR and CARP||00:00:5E:00:01:00||00:00:5E:00:01:ff||256|