Page 1 of 1
Local bridge with DHCP
Posted: Mon Aug 30, 2021 3:28 pm
by tcdaly
When creating a local bridge, the SoftEther documentation recommends that the network interface bridged to is not allocated an IP address. The local bridge configuration also requires a DHCP server. In my case, I have no option but to run the DHCP server on the same Linux box as SoftEther and the local bridge.
However the DHCP server seems to expect an IP address allocated to the network interface it is bound to. I cannot see a way of running the DHCP server without an IP address.
How important is it not to have an IP address allocated to the network interface?
Re: Local bridge with DHCP
Posted: Mon Aug 30, 2021 3:37 pm
by eddiewu
This recommendation is for those who bridge the virtual hub to an existing server side LAN segment. The server can either be or not be part of it. Therefore, there must be an working DHCP server.
Re: Local bridge with DHCP
Posted: Mon Aug 30, 2021 5:39 pm
by tcdaly
Thank you. I can see no way of implementing a working DHCP server unless the NIC that is bridged to has an IP address assigned to it.
Re: Local bridge with DHCP
Posted: Tue Aug 31, 2021 8:46 am
by tcdaly
If you consider this DHCP server configuration fragment:
Code: Select all
subnet 10.1.1.0 netmask 255.255.255.0 {
range 10.1.1.50 10.1.1.99;
option routers 10.1.1.1;
option broadcast-address 10.1.1.255;
}
If the network interface has no IP address, the DHCP server has no means of associating the subnet with the interface. So the server fails to start with the error:
Code: Select all
Aug 29 22:33:08 lillie dhcpd[835]: Not configured to listen on any interfaces!
Aug 29 17:58:19 lillie dhcpd[2527]: No subnet declaration for eth1 (no IPv4 addresses).
Aug 29 17:58:19 lillie dhcpd[2527]: ** Ignoring requests on eth1. If this is not what
Aug 29 17:58:19 lillie dhcpd[2527]: you want, please write a subnet declaration
Aug 29 17:58:19 lillie dhcpd[2527]: in your dhcpd.conf file for the network segment
Aug 29 17:58:19 lillie dhcpd[2527]: to which interface eth1 is attached. **
Re: Local bridge with DHCP
Posted: Tue Aug 31, 2021 11:57 am
by eddiewu
I said it is only relevant to who has a working LAN on the server side. If you don’t then you are not relevant.
Re: Local bridge with DHCP
Posted: Mon Sep 13, 2021 11:08 pm
by cedar
If the local bridge is connected to a tap device, you should set the IP address.
You can also set an IP address if you are locally bridging to a physical NIC, but be aware that that IP address cannot communicate with the Virtual Hub.
When operating purely as a bridge, it is estimated that the CPU load can be reduced by disconnecting the TCP/IP stack of the OS without setting the IP address. (Although this estimation is doubtful)