Frequent floating of a multi-homed client

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TinyTim
OpenVpn Newbie
Posts: 1
Joined: Sun Sep 12, 2021 1:02 am

Frequent floating of a multi-homed client

Post by TinyTim » Sun Sep 12, 2021 1:57 am

Hi, I have an OpenVPN set up running in server mode at a cloud service and I have a client connecting in from a multi-homed virtual box guest. The client has a default gateway to the virtual box NAT which is connected to the host Windows 10 which is again multi-homed to a 4g lte modem and an ADSL service. Additionally, the client has also a default gateway to the ADSL service by a bridged set up with the windows 10 ADSL.

So, routing table for the client is like this:

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Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         10.0.3.2        0.0.0.0         UG    0      0        0 eth1 <---- NAT to guest which is dual-homed to 4G and ADSL
default         192.168.1.1     0.0.0.0         UG    0      0        0 eth0 <---- Bridged to guest which is connected to ADSL
10.0.3.0        *               255.255.255.0   U     0      0        0 eth1
10.13.13.0      10.13.13.17     255.255.255.0   UG    0      0        0 tun0
10.13.13.17     *               255.255.255.255 UH    0      0        0 tun0
127.0.0.1       *               255.255.255.255 UH    0      0        0 lo
192.168.1.0     *               255.255.255.0   U     0      0        0 eth0
Now, as I understand it, OpenVPN should connect via only the first route which in my case happens majority of the times through the first default gateway. But apparently, OpenVPN likes to float around the two IPs quite frequently. Although this is a nice thing happening but I never expected this. I just want you guys to confirm if this is an expected behavior as I would have to be quite reliably working with OpenVPN for the next few months and I want it to be all consistent.

My server management interface log goes like this:

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LOG:1631411624,,Float requested for peer 0 to 59.90.254.199:43831
>LOG:1631411624,,peer 0 (tclinx) floated from 157.40.199.68:49429 to [AF_INET]59.90.254.199:43831
>LOG:1631411635,,Float requested for peer 0 to 157.40.199.68:49429
>LOG:1631411635,,peer 0 (tclinx) floated from 59.90.254.199:43831 to [AF_INET]157.40.199.68:49429
>LOG:1631411674,,Float requested for peer 0 to 59.90.254.199:43831
>LOG:1631411674,,peer 0 (tclinx) floated from 157.40.199.68:49429 to [AF_INET]59.90.254.199:43831
>LOG:1631411675,,Float requested for peer 0 to 157.40.199.68:49429
>LOG:1631411675,,peer 0 (tclinx) floated from 59.90.254.199:43831 to [AF_INET]157.40.199.68:49429
>LOG:1631411715,,Float requested for peer 0 to 59.90.254.199:43831
>LOG:1631411715,,peer 0 (tclinx) floated from 157.40.199.68:49429 to [AF_INET]59.90.254.199:43831
The IP starting with 59.90.*.* is the ADSL and the other 4G.

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