RB4011 L2MTU bug.

RouterOS General
1

Background:
model: RB4011iGS+
current-firmware: 6.47
10 R name=“sfp-sfpplus1” default-name=“sfp-sfpplus1” mtu=4000 l2mtu=4200 (…)

/ping 10.250.9.245 size=3200 do-not-fragment
SEQ HOST SIZE TTL TIME STATUS
0 10.250.9.245 3200 64 5ms

(reboot)

/ping 10.250.9.245 size=3200 do-not-fragment
SEQ HOST SIZE TTL TIME STATUS
0 10.250.9.245 timeout

lets apply the magic fix now:
/interface ethernet> set sfp-sfpplus1 l2mtu=4020
/interface ethernet> set sfp-sfpplus1 l2mtu=4200

/ping 10.250.9.245 size=3200 do-not-fragment
SEQ HOST SIZE TTL TIME STATUS
0 10.250.9.245 3200 64 4ms

…and all is great in the world again. At least until next reboot.
Please fix. KTHXBYE.

2

This is a user forum, it’s not the right avenue to post potential bugs.

Please email support@mikrotik.com with full details - that is the proper way to get this investigated by MikroTik.