Data Domain: Invalid MTU Causes VLAN Interface Failure After Reboot
Summary: A VLAN interface became inaccessible after a reboot because an invalid MTU configuration was rejected during initial configuration but still persisted in the registry, causing the interface to fail when the system later attempted to apply the invalid MTU during interface initialization. ...
Symptoms
Data Domain becomes inaccessible following a reboot or interface down and up operation.
VLAN interface status shows as down or disabled.
Attempting to configure an MTU larger than the parent interface MTU returns a validation error.
The interface may continue running with the previously configured MTU until a reboot or interface restart occurs.
After reboot, the affected VLAN interface fails to come up.
# net config veth1.100 mtu 9000
Configuring interface... **** vlan mtu, 9000, is bigger than the base, veth1, mtu, 1500
!!!! juno-193 YOUR DATA IS IN DANGER !!!! # reg_cmd show config_master.net | grep veth1
config_master.net.veth1.100.bonding.mode = dontcare
config_master.net.veth1.100.enabled = true
config_master.net.veth1.100.mtu_state = 1
config_master.net.veth1.100.mtusize = 9000
veth1.100 yes running no 7.7.7.7 255.255.255.0 n/a connected
xxxx::xxxx:xxxx:fe8e:e47c** /64
!!!! juno-193 YOUR DATA IS IN DANGER !!!! # reboot
Broadcast message from root (pts/0) : The system is going down for reboot NOW!
!!!! juno-193 YOUR DATA IS IN DANGER !!!! #
veth1 yes running no 9.9.9.9 255.255.255.0 n/a roundrobin: eth3a,eth3b connected
xxxx:xxxx:xxxx:xxxx:ac0:ebff:fe8e:e47c** /64
xxxx::xxxx:xxxx:fe8e:e47c** /64
xxxx:xxxx:xxxx:bea5:ac0:ebff:fe8e:e47c** /64
veth1.100 yes down no 7.7.7.7 255.255.255.0 n/a disabledCause
When an invalid MTU value is configured on a VLAN interface associated with a bonded interface, the system correctly rejects the configuration and continues operating with the previously configured MTU.
However, the invalid MTU value is still written to the registry and is not reverted.
During a reboot, or when the interface is brought down and back up, the system reads the persisted configuration from the registry and attempts to apply the invalid MTU.
Since the MTU validation fails during interface initialization, the VLAN interface is unable to come online. Even though the MTU configuration failed, the invalid value remains stored and is reapplied on subsequent interface initialization events.
Resolution
If the issue has already occurred:
- Access the system through iDRAC, serial console, or another out-of-band management method.
- Configure a valid MTU value that does not exceed the MTU of the parent interface.
- Bring the interface back online if required.
Example:
>net config veth1.100 mtu 1500
Preventative Action
Until a permanent fix is available, whenever an MTU configuration attempt fails validation, immediately rerun the command using a valid MTU value.
Example:
net config veth1.100 mtu 9000 Configuring interface...**** vlan mtu, 9000, is bigger than the base, veth1, mtu, 1500
Correct it immediately:
net config veth1.100 mtu 1500
This ensures the registry is updated with a valid value and prevents the interface from failing after a reboot or interface restart.
Engineering is planning a fix for an upcoming DDOS release.