BUG? Switching network bridges causes "Default gateway already exists" error

Jon Jaroker

Renowned Member
Apr 5, 2012
Upon my first installation of Proxmox, I entered the LAN parameters into the setup wizard. This was assigned to eth0+vmbr0. Everything worked fine upon the initial boot of the host.

I attempted to change the network setup using the web interface. My network uses eth1+br1 for the LAN connection. This is just a cosmetic change so that the new server uses the same conventions as my other servers.

Using the "Network" tab for the host, my steps were:

  1. Edit vmbr0 so that it uses my WAN parameters. The "Gateway" in the "Edit: Bridge" dialog box was replaced with the WAN gateway.
  2. Reboot the server for the changes to take effect.
  3. Logged into the server using the WAN IP address. Everything is still working fine.
  4. Attempt to "Create" a bridge vmbr1 for the LAN connection. In the Edit:Bridge dialog box, I entered the LAN's gateway (which used to be assigned to vmbr0, but was changed in step 1).
  5. Error message pops up: Parameter verification failed (400). Gateway: Default gateway already exists on interface vmbr0. This is not true.

In the /etc/network/interfaces file, I see the correct gateway being used for vmbr0. The web interface shows this correct gateway on in the "Network" page.

I believe there is a conflict between the network configuration file on the host and the verification data used by the web interface.

-- Jon
post your /etc/network/interfaces file.


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