Super User Asked on November 3, 2021
I have a very annoying problem on my windows server.
This Server has multiple interfaces to interact with many different things. Primarily it is a Hyper-V-Server, thus it requires connectivity to multiple networks for different services used by the virtual machines.
Because it’s Hyper-V, it uses Hyper-V-Extensible Interfaces, configured in the Hyper-V-Manager.
The server is also connected to the company network / aka. the internet.
This company network interface is the only one that uses DHCP, so I automatically get IP 10.20.xx.xx / Gateway 10.20.xx.xx / DNS 10.20.xx.xx
(Let’s call this interface ASIX, because it’s an adapter)
There is another interface (let’s call it ETH1) which is connected to a cisco L2/L3, which handles all the routing to the different services or networks.
All of my static routes lead to that router. I removed the default gateway on that interface.
Then there is a last interface (let’s call it ETH0) which is only for switch-management and so forth. It’s a simple vlan connected to all routers/switches. This interface can be ignored, as it is only a local network, without routing or gateways set.
To access the services, I configured ALL necessary routes beyond the ETH1 interface, like so:
route -p ADD 10.1.2.0 MASK 255.255.255.248 172.19.8.100 IF 13
route -p ADD 10.1.3.0 MASK 255.255.255.248 172.19.8.100 IF 13
route -p ADD 10.1.4.0 MASK 255.255.255.248 172.19.8.100 IF 13
route -p ADD 10.1.6.0 MASK 255.255.255.248 172.19.8.100 IF 13
route -p ADD 192.19.8.0 MASK 255.255.252.0 172.19.8.100 IF 13
route -p ADD 192.19.20.0 MASK 255.255.252.0 172.19.8.100 IF 13
route -p ADD 192.19.28.0 MASK 255.255.252.0 172.19.8.100 IF 13
route -p ADD 172.19.8.0 MASK 255.255.255.0 172.19.8.100 IF 13
route -p ADD 172.20.10.0 MASK 255.255.255.0 172.19.8.100 IF 13
route -p ADD 172.20.20.0 MASK 255.255.255.0 172.19.8.100 IF 13
route -p ADD 172.20.30.0 MASK 255.255.255.0 172.19.8.100 IF 13
These routes were all accessible and working fine while I’ve been connected to the company network directly (=> ASIX).
BUT…
For some weird reason, when I switched the ASIX interface to a WLAN-Interface, due to ongoing changes in the company-network, those routes wouldn’t work anymore at all.
Generally, the routes are ALL working correctly from the router 172.19.8.100, so the issue definitly is with the server.
The difference between using the company network directly and the newly connected WLAN-Interface is the WLAN-Router between the server and the company-network.
So before I directly got a company address (10.20.xx.xx), now I’m getting a DHCP address from the router. (192.168.1.x)
And I have no idea why this would make any difference at all, considering that there’s no overlapping networks and everything is "properly configured" from my perspective.
Even the network that is statically configured attempts to go via 192.168.1.0, which it really shouldn’t:
PS C:Windowssystem32> tracert -d 172.19.8.100
Routenverfolgung zu 172.19.8.100 über maximal 30 Hops
1 2 ms 2 ms 2 ms 192.168.1.1
2 2 ms 2 ms 2 ms 10.20.215.250
...and so forth, going the wrong way...
When disabling the WLAN/Intranet interface everything works normally again, I just don’t have internet / company access then.
Can anyone tell me if there’s some internal handling of these routes, that work against me?
Windows shenanigans maybe?
I have a hunch that 2 default-gateways are not a "good idea", but I feel like with static routes set in place it shouldn’t matter that much.
Also, I’ve manually set the interface metric, so that the internal network is generally lower (2 vs 50).
UPDATE:
I followed the tip in the comments and removed the second default-gateway leading to the cisco router. (172.19.8.100)
I also set all interface metrics back to automatic again.
The network metric was just a quick attempt to get a workaround, but it didn’t affect the situation at all.
This is what my route print looks like:
PS C:Windowssystem32> route print
===========================================================================
Schnittstellenliste
17...00 15 5d d7 f1 05 ......Hyper-V Virtual Ethernet Adapter #5
11...54 b2 03 18 aa 7e ......Hyper-V Virtual Ethernet Adapter #3
13...54 b2 03 18 aa 7f ......Hyper-V Virtual Ethernet Adapter
27...6c f0 49 6c 42 6d ......ASIX AX88772C USB2.0 to Fast Ethernet Adapter
1...........................Software Loopback Interface 1
===========================================================================
IPv4-Routentabelle
===========================================================================
Aktive Routen:
Netzwerkziel Netzwerkmaske Gateway Schnittstelle Metrik
0.0.0.0 0.0.0.0 192.168.1.1 192.168.1.121 36
10.1.1.0 255.255.255.248 172.19.8.100 172.19.8.250 36
10.1.2.0 255.255.255.248 172.19.8.100 172.19.8.250 36
10.1.3.0 255.255.255.248 172.19.8.100 172.19.8.250 36
10.1.4.0 255.255.255.248 172.19.8.100 172.19.8.250 36
10.1.6.0 255.255.255.248 172.19.8.100 172.19.8.250 36
127.0.0.0 255.0.0.0 Auf Verbindung 127.0.0.1 331
127.0.0.1 255.255.255.255 Auf Verbindung 127.0.0.1 331
127.255.255.255 255.255.255.255 Auf Verbindung 127.0.0.1 331
172.19.8.0 255.255.255.0 172.19.8.100 172.19.8.250 36
172.19.8.250 255.255.255.255 Auf Verbindung 172.19.8.250 291
172.20.2.0 255.255.255.0 Auf Verbindung 172.20.2.100 281
172.20.2.100 255.255.255.255 Auf Verbindung 172.20.2.100 281
172.20.2.255 255.255.255.255 Auf Verbindung 172.20.2.100 281
172.20.10.0 255.255.255.0 172.19.8.100 172.19.8.250 36
172.20.20.0 255.255.255.0 172.19.8.100 172.19.8.250 36
172.20.30.0 255.255.255.0 172.19.8.100 172.19.8.250 36
172.127.0.0 255.255.0.0 Auf Verbindung 172.127.0.1 271
172.127.0.1 255.255.255.255 Auf Verbindung 172.127.0.1 271
172.127.255.255 255.255.255.255 Auf Verbindung 172.127.0.1 271
192.19.8.0 255.255.252.0 172.19.8.100 172.19.8.250 36
192.19.20.0 255.255.252.0 172.19.8.100 172.19.8.250 36
192.19.28.0 255.255.252.0 172.19.8.100 172.19.8.250 36
192.168.1.0 255.255.255.0 Auf Verbindung 192.168.1.121 291
192.168.1.121 255.255.255.255 Auf Verbindung 192.168.1.121 291
192.168.1.255 255.255.255.255 Auf Verbindung 192.168.1.121 291
224.0.0.0 240.0.0.0 Auf Verbindung 127.0.0.1 331
224.0.0.0 240.0.0.0 Auf Verbindung 172.20.2.100 281
224.0.0.0 240.0.0.0 Auf Verbindung 172.19.8.250 291
224.0.0.0 240.0.0.0 Auf Verbindung 172.127.0.1 271
224.0.0.0 240.0.0.0 Auf Verbindung 192.168.1.121 291
255.255.255.255 255.255.255.255 Auf Verbindung 127.0.0.1 331
255.255.255.255 255.255.255.255 Auf Verbindung 172.20.2.100 281
255.255.255.255 255.255.255.255 Auf Verbindung 172.19.8.250 291
255.255.255.255 255.255.255.255 Auf Verbindung 172.127.0.1 271
255.255.255.255 255.255.255.255 Auf Verbindung 192.168.1.121 291
===========================================================================
Ständige Routen:
Netzwerkadresse Netzmaske Gatewayadresse Metrik
10.1.1.0 255.255.255.248 172.19.8.100 1
10.1.2.0 255.255.255.248 172.19.8.100 1
10.1.3.0 255.255.255.248 172.19.8.100 1
10.1.4.0 255.255.255.248 172.19.8.100 1
10.1.6.0 255.255.255.248 172.19.8.100 1
192.19.8.0 255.255.252.0 172.19.8.100 1
192.19.20.0 255.255.252.0 172.19.8.100 1
192.19.28.0 255.255.252.0 172.19.8.100 1
172.19.8.0 255.255.255.0 172.19.8.100 1
172.20.10.0 255.255.255.0 172.19.8.100 1
172.20.20.0 255.255.255.0 172.19.8.100 1
172.20.30.0 255.255.255.0 172.19.8.100 1
===========================================================================
Relevant Network-Information:
10.1.x.0 => Networks accessible via Cisco Router
192.19.x.0 => Networks accessible via Cisco Router
172.20.2.0 => Management Network / Seperate Interface ETH0
172.19.8.0 => Cisco Router / Backbone Network
172.19.8.100 => Cisco Router
172.19.8.250 => Static IP Interface / Interface ETH1
192.168.1.0 => WLAN-Router Network
192.168.1.1 => WLAN-Router
192.168.1.121 => Current Dynamic IP on Interface with GW to WLAN-Router
(In this issue, it doesn’t matter if I’m connected by WLAN or LAN to the Router, it both doesn’t work)
This question can best be answered with:
"When complex things don't work, check off the simple things first."
Thomas was completely right about the part with disabling the second default gateway, since I've already had all the static routes configured it wasn't really necessary.
Then on the other hand I was completely wrong about the part that the interface worked. I assumed that it did, because I haven't gotten any errors on it, but also didn't bother to double-check myself.
When looking closely into the interface status, I noticed that I didn't receive any packets at all. I checked again with the cisco router configuration noticed that the port which I want to be connected on, actually is a different one.
This happened during a recent 'cable-management', which incidently happened simultanously with the change to the temporary router. I wrongly assumed that the fault lies within the temporary router.
Everything else in this question actually was correctly configured, except the default-gateway part.
Answered by HackXIt on November 3, 2021
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