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chberger avatar image
chberger asked

Cerbo GX announces two IP-Adresses

I connected my Cerbo GX to my LAN. In the LAN is a DSL-Router, which also has a DHCP-server. When the Cerbo GX boots, it shows up in the network list with two IP-addresses: one private class B IP-addres (192.168.xx.yy) which is assigned by the DHCP server in my router, and a second link local address (169.254.xx.yy) with a randomly generated MAC-address (at least it seems so ...).


I wonder what the link-local address is good for / is used for and, if it is not needed as the Cerbo is fully accessible through the Class B IPv4 (asigned by the DHCP-Server), how can I turn that off?


WLAN and Bluetooth are turned off, BTW ...

Firmware is 2.85

cerbo gxTCP IP Networking
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8 Answers
mvader (Victron Energy) avatar image
mvader (Victron Energy) answered ·

Hey all,

Having two IP addresses, and even two different mac addresses on the same physical interface, aka ethernet port, is perhaps a bit unusual but also within official IP specifications and supported by many OSes and done often in for example servers.

The GX has two IP addresses on its ethernet port:

1) the most used one, defaults to DHCP and can also be set to a fixed IP address by the user. The mac address for this one is the one on the label and static - assigned during production.

2) a link local address. 169.254.xxx.xxx. The mac address for this one is a random one, generated at boot.


Though not well known in general, the link local mechanism is super useful; and we have it there - always, so also when DHCP for the other one works - to allow communication between devices to work always. Without depending on a proper functioning auto config normally done by having a dhcp server on a router.

For example on boats, this allows the MFD and the Gx to communicate and perform their functions as soon as the installer plugs both of them in a switch. No knowledge needed about IP addressing and no need for a router to be in there and working.


Having said that: does anyone of you have a problem in their network that is possibly because of this? If yes, what, aside from warnings about possible problems shown in a router or dhcp server, is the problem?

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Jason - UK avatar image
Jason - UK answered ·

I think one is for local access and the other is external access. Somewhat an assumption but looking at my home network, I access the remote console though one IP address but the VRM appears to be using the other.

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Henk van Rooyen avatar image
Henk van Rooyen answered ·

Similar problem, but different as well:

Cerbo GX connected to UniFi network. UniFi controller complains about multiple devices using the same IP address. On investigating further, my Cerbo somehow connects to my network with two different MAC addresses, but both have the same (nonlocal) IP address. Screenshot attached demonstrates the situation - note one MAC address is aliased on the list view, see MAC in detail box on right of screenshot.

To add to the weirdness: After a recent problem with a non-reachable Cerbo (which had me replace a switch as well as the Cerbo, only to have the problem recur) I leave the Cerbo WiFi connection on as a possible backup. So now my UniFi controller complains about an additional "multiple device same IP address" issue - this for the Cerbo's local WLAN IP address. Unfortunately this issue is weirdly intermittent, so I do not have a screenshot to demonstrate it (but it is essentialy the same problem, except for it being Local, WiFi connections from the Cerbo).

2022-12-23 (1).png


2022-12-23-1.png (232.1 KiB)
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marv21 avatar image marv21 commented ·
Got the same Problem now...
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Sten avatar image
Sten answered ·

169.254.xxx.yyy is a default assigned ip to an interface witch is not configurated with a manual or a assigned dhcp address.

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approved-ok avatar image
approved-ok answered ·

Got the same problem - issues although network security problems on managed switch-ports with mac-adressing.
is there a know way to dissable the second ip 169.254.xxx.xxx ?
would be very helpfull, thx

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Henk van Rooyen avatar image
Henk van Rooyen answered ·

@approved_ok I received an answer as to why it is happening on another thread. See https://community.victronenergy.com/questions/176961/cerbo-gx-duplicate-ip-addresses.html?childToView=176984#answer-176984

Unfortunately it only explains why, and does not solve the problem. I can block the addresses, but still receive the messages. Cannot block the MAC address because that would block legitimate traffic from the device as well.

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kenzo avatar image
kenzo answered ·

See here: https://community.victronenergy.com/questions/49662/ccgx-ethernet-mac-address-changing-link-local.html?childToView=268605#comment-268605

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shop6 avatar image
shop6 answered ·

mvader: "Having said that: does anyone of you have a problem in their network that is possibly because of this? If yes, what, aside from warnings about possible problems shown in a router or dhcp server, is the problem?"

May be? I have a problem with giving OpenDTU a fix ip via fritz.box/DHCP. Using DTU to control a pv inverter at MultiplusII-AC-OUT. See issue for details.

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Related Resources

Cerbo GX product page

GX family product range

Cerbo GX & GX Touch datasheet

Cerbo GX Manual

Venus root access document

Additional resources still need to be added for this topic