we have several VLANs/Subnets and the backup server has a network connection to every subnet, so that the client could see the server.
I have some clients in the 192.168.15.x sub net and they see the broadcast from the server 192.168.15.72:
1 0.000000 192.168.15.72 255.255.255.255 UDP 60 35623 → 35622 Len=1
and the server is directly connecting to the client
2 0.000024 192.168.15.72 192.168.15.152 UDP 60 35623 → 35622 Len=1
But I also see, that the server is trying to reach this client from his other network adapters:
3 0.000057 192.168.70.72 192.168.15.152 UDP 60 35623 → 35622 Len=1
4 0.000144 192.168.50.72 192.168.15.152 UDP 60 35623 → 35622 Len=1
5 0.000145 192.168.40.72 192.168.15.152 UDP 60 35623 → 35622 Len=1
6 0.000146 192.168.30.72 192.168.15.152 UDP 60 35623 → 35622 Len=1
so the client tries to respond to the server on the wrong subnet (70):
7 0.236490 192.168.15.152 192.168.70.72 UDP 50 35622 → 35623 Len=8
Why does the server try to reach the client over ALL network cards?
He has a correct routing table:
Ziel Router Genmask Flags MSS Fenster irtt Iface
default router4.intern. 0.0.0.0 UG 0 0 0 ens160
192.168.15.0 0.0.0.0 255.255.255.0 U 0 0 0 ens160
192.168.30.0 0.0.0.0 255.255.255.0 U 0 0 0 ens192
192.168.40.0 0.0.0.0 255.255.255.0 U 0 0 0 ens224
192.168.50.0 0.0.0.0 255.255.255.0 U 0 0 0 ens161
192.168.70.0 0.0.0.0 255.255.255.0 U 0 0 0 ens256
and knows that he could reach clients in the .15 subnet over interface ens160