When most people deploy an Open vSwitch configuration for virtual networking using the NORMAL rule, that is, using L2 learning, they do not think about configuring the size of the Forwarding DataBase (FDB).
When hardware-based switches are used, the FDB size is generally rather large and the large FDB size is a key selling point. However for Open vSwitch, the default FDB value is rather small, for example, in version 2.9 and earlier it is only 2K entries. Starting with version 2.10 the FDB size was increased to 8K entries. Note that for Open vSwitch, each bridge has its own FDB table for which the size is individually configurable.
This blog explains the effects of configuring too small an FDB table, how to identify which bridge is suffering from too small an FDB table, and how to configure the FDB table size appropriately.
Continue reading “Troubleshooting FDB table wrapping in Open vSwitch”