Symptoms
Jumbo frames are disabled by default for Mellanox ConnectX-4 and ConnectX-5 devices using the mlxvf5 driver (i.e., many BIG-IP Virtual Edition (VE) configurations). Packets larger than 1500 bytes are silently dropped. Only packets up to 1500 bytes are supported when jumbo framers are disabled.
Impact
Packets larger than 1500 bytes are dropped without a warning.
Conditions
BIG-IP VE with SR-IOV using Mellanox ConnectX-4 or ConnectX-5 NICs.
Typically this represents VE configurations running on private Cloud environments such as VMware, KVM, OpenStack, and others.
Note: You can determine your environment by running the following commands:
# tmctl -d blade tmm/device_probed
# tmctl -d blade xnet/device_probed
Configurations exhibiting this issue either:
1. reports a value of 'mlxvf5' in the driver_in_use column in tmm/device_probed, and possibly reports 'tmctl: xnet/device_probed: No such table.'
2. reports a value of 'xnet' in the driver_in_use column in tmm/device_probed, and a value of 'mlxvf5' in the driver_in_use column in xnet/device_probed.
Workaround
Enable jumbo frames and then restart tmm.
1. Add the following line to /config/xnet_init.tcl:
drvcfg mlxvf5 jumbo_support 1
2. Restart tmm:
bigstart restart tmm
Important: There are two possible mlxvf5 drivers. It is possible to enable jumbo frames only for the xnet-based driver.
Important: Enabling jumbo frames causes a performance loss for 1500-byte-size packet, but offers higher throughput at lower CPU usage for larger packets. Note that 1500 bytes is the most common size for internet packets.
