Locally administered MAC addresses

Good Afternoon,

I have my ubuntu desktop and a W5500 (wiznet ethernet chip) based device connected via a mikrotik CRS328 switch. The switch is in its default configuration.

My desktop has a static IP of 192.168.88.2 and the W5500 device has a static IP of 192.168.88.3. The W5500 has a UDP socket listening on port 12000.

I have noticed that I can send packets from my desktop to the W5500 device only when I set the first byte of the mac to 0x24 rather than 0x26. Put another way, if I set the mac on the W5500 to be locally administered, it seems to get ignored by the switch (ARP requests fail).

Why is this?

Many Thanks!

Is your CRS running ROS or SwOS?

In principle devices running ROS don’t have problems with LLAs. Unless there’s some config interfering. You may post switch config so we can check for anything suspicious (execute /export file=anynameyouwish in terminal window, fetch file off device, open it with a text editor and redact any sensible information such as serial number … but don’t over do it) and copy-paste it in a post (enclose them in [__code] [/code] environment).

If CRS is running SwOS, then you’ll have to post some screenshots of configuration (but do it in SwitchOS section of this forum).

Thanks for the quick response. Here is my config file. The w5500 is on ether6.

A few changes from the default that I noticed when I reviewed the config:
– ether6 is marked as trusted (problem exists whether this is checked or not)
– stp is disabled (problem exists whether this is enabled or not)

# jan/02/1970 20:22:05 by RouterOS 6.48.6
# software id = EIP4-M7SU
#
# model = CRS328-24P-4S+
/interface bridge
add admin-mac=48:A9:8A:2B:6C:11 arp-timeout=10s auto-mac=no comment=defconf \
    name=bridgeLocal protocol-mode=none
/interface ethernet
set [ find default-name=ether6 ] poe-out=off
/interface ethernet switch port
set 5 limit-broadcasts=no
/interface list
add name=WAN
add name=LAN
/interface wireless security-profiles
set [ find default=yes ] supplicant-identity=MikroTik
/ip hotspot profile
set [ find default=yes ] html-directory=hotspot
/interface bridge port
add bridge=bridgeLocal comment=defconf interface=ether1
add bridge=bridgeLocal comment=defconf interface=ether2
add bridge=bridgeLocal comment=defconf interface=ether3
add bridge=bridgeLocal comment=defconf interface=ether4
add bridge=bridgeLocal comment=defconf interface=ether5
add bridge=bridgeLocal comment=defconf interface=ether6 trusted=yes
add bridge=bridgeLocal comment=defconf interface=ether7
add bridge=bridgeLocal comment=defconf interface=ether8
add bridge=bridgeLocal comment=defconf interface=ether9
add bridge=bridgeLocal comment=defconf interface=ether10
add bridge=bridgeLocal comment=defconf interface=ether11
add bridge=bridgeLocal comment=defconf interface=ether12
add bridge=bridgeLocal comment=defconf interface=ether13
add bridge=bridgeLocal comment=defconf interface=ether14
add bridge=bridgeLocal comment=defconf interface=ether15
add bridge=bridgeLocal comment=defconf interface=ether16
add bridge=bridgeLocal comment=defconf interface=ether17
add bridge=bridgeLocal comment=defconf interface=ether18
add bridge=bridgeLocal comment=defconf interface=ether19
add bridge=bridgeLocal comment=defconf interface=ether20
add bridge=bridgeLocal comment=defconf interface=ether21
add bridge=bridgeLocal comment=defconf interface=ether22
add bridge=bridgeLocal comment=defconf interface=ether23
add bridge=bridgeLocal comment=defconf interface=ether24
add bridge=bridgeLocal comment=defconf interface=sfp-sfpplus1
add bridge=bridgeLocal comment=defconf interface=sfp-sfpplus2
add bridge=bridgeLocal comment=defconf interface=sfp-sfpplus3
add bridge=bridgeLocal comment=defconf interface=sfp-sfpplus4
/interface list member
add interface=ether1 list=WAN
add interface=ether2 list=LAN
add interface=ether3 list=LAN
add interface=ether4 list=LAN
add interface=ether5 list=LAN
add interface=ether6 list=LAN
add interface=ether7 list=LAN
add interface=ether8 list=LAN
add interface=ether9 list=LAN
add interface=ether10 list=LAN
add interface=ether11 list=LAN
add interface=ether12 list=LAN
add interface=ether13 list=LAN
add interface=ether14 list=LAN
add interface=ether15 list=LAN
add interface=ether16 list=LAN
add interface=ether17 list=LAN
add interface=ether18 list=LAN
add interface=ether19 list=LAN
add interface=ether20 list=LAN
add interface=ether21 list=LAN
add interface=ether22 list=LAN
add interface=ether23 list=LAN
add interface=ether24 list=LAN
add interface=sfp-sfpplus1 list=LAN
add interface=sfp-sfpplus2 list=LAN
add interface=sfp-sfpplus3 list=LAN
add interface=sfp-sfpplus4 list=LAN
/ip dhcp-client
add comment=defconf disabled=no interface=bridgeLocal
/system identity
set name=RouterOS
/system routerboard settings
set boot-os=router-os

You’re right, config doesn’t contain anything which would explain behaviour you’re observing.