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I have 2 servers (Windows Server 2012 R2), with each having (more than) 2 network cards. I want both server to use 1 network card for "The Internet", and 1 network card to communicate directly with the other server. (There is also a 3rd server present, but I will not go into details now.)

Server 1 has public IP 63.148.179.243 (interface 14) and local IP 192.168.211.13 (interface 15)
Server 2 has public IP 63.148.179.244 and local IP 192.168.211.15
(interface 15 connected directly to Server 2)

I want the servers to communicate directly, even if I would address them via their public IP's. I assume I have to add a route like this on Server 1: route -p add 63.148.179.244/32 192.168.211.13 metric 10 if 15

But even after doing this, if I open a browser on Server 1 and I download a huge file from http://63.148.179.244/hugeFile.txt, I see that the network card that is connected to the Internet is getting the full load, and the download speed is much lower than what I would expect.

I also tried it slightly different, with no better result, using: route -p add 63.148.179.244/32 192.168.211.15 metric 10 if 15 and route -p add 63.148.179.244/32 192.168.211.13 metric 10 if 14

When adding the route, it looks like this:

C:\Windows\system32>route -p add 63.148.179.244/32 192.168.211.13 metric 10 if 15
 OK!

C:\Windows\system32>route print
===========================================================================
Interface List
 20...02 c5 d5 76 49 2c ......Microsoft Failover Cluster Virtual Adapter
 13...94 57 a5 57 86 6d ......HP Ethernet 1Gb 4-port 331i Adapter #2
 15...94 57 a5 57 86 6e ......HP Ethernet 1Gb 4-port 331i Adapter #3
 14...94 57 a5 57 86 6c ......HP Ethernet 1Gb 4-port 331i Adapter
  1...........................Software Loopback Interface 1
 16...00 00 00 00 00 00 00 e0 Microsoft ISATAP Adapter #2
 17...00 00 00 00 00 00 00 e0 Microsoft 6to4 Adapter
 18...00 00 00 00 00 00 00 e0 Microsoft ISATAP Adapter #3
 19...00 00 00 00 00 00 00 e0 Microsoft ISATAP Adapter #4
===========================================================================

IPv4 Route Table
===========================================================================
Active Routes:
Network Destination        Netmask          Gateway       Interface  Metric
          0.0.0.0          0.0.0.0   63.148.179.241   63.148.179.243    276
   63.148.179.240  255.255.255.240         On-link    63.148.179.243    276
   63.148.179.242  255.255.255.255         On-link    192.168.211.12     20
   63.148.179.243  255.255.255.255         On-link    63.148.179.243    276
   63.148.179.244  255.255.255.255         On-link    192.168.211.13     20
   63.148.179.251  255.255.255.255         On-link    63.148.179.243    276
   63.148.179.252  255.255.255.255         On-link    63.148.179.243    276
   63.148.179.255  255.255.255.255         On-link    63.148.179.243    276
        127.0.0.0        255.0.0.0         On-link         127.0.0.1    306
        127.0.0.1  255.255.255.255         On-link         127.0.0.1    306
  127.255.255.255  255.255.255.255         On-link         127.0.0.1    306
    192.168.211.0    255.255.255.0         On-link    192.168.211.12    266
    192.168.211.0    255.255.255.0         On-link    192.168.211.13    266
   192.168.211.12  255.255.255.255         On-link    192.168.211.12    266
   192.168.211.13  255.255.255.255         On-link    192.168.211.13    266
  192.168.211.255  255.255.255.255         On-link    192.168.211.12    266
  192.168.211.255  255.255.255.255         On-link    192.168.211.13    266
        224.0.0.0        240.0.0.0         On-link         127.0.0.1    306
        224.0.0.0        240.0.0.0         On-link    63.148.179.243    276
        224.0.0.0        240.0.0.0         On-link    192.168.211.12    266
        224.0.0.0        240.0.0.0         On-link    192.168.211.13    266
  255.255.255.255  255.255.255.255         On-link         127.0.0.1    306
  255.255.255.255  255.255.255.255         On-link    63.148.179.243    276
  255.255.255.255  255.255.255.255         On-link    192.168.211.12    266
  255.255.255.255  255.255.255.255         On-link    192.168.211.13    266
===========================================================================
Persistent Routes:
  Network Address          Netmask  Gateway Address  Metric
          0.0.0.0          0.0.0.0   63.148.179.241  Default
   63.148.179.242  255.255.255.255   192.168.211.12      10
   63.148.179.244  255.255.255.255   192.168.211.13      10
===========================================================================

IPv6 Route Table
===========================================================================
Active Routes:
 If Metric Network Destination      Gateway
 17   1026 ::/0                     2002:c058:6301::1
  1    306 ::1/128                  On-link
 17   1025 2002::/16                On-link
 17    281 2002:3e94:b3f3::3e94:b3f3/128
                                    On-link
 17    281 2002:3e94:b3fb::3e94:b3fb/128
                                    On-link
 17    281 2002:3e94:b3fc::3e94:b3fc/128
                                    On-link
 14    276 fe80::/64                On-link
 13    266 fe80::/64                On-link
 15    266 fe80::/64                On-link
 15    266 fe80::196e:792:9b88:76d9/128
                                    On-link
 13    266 fe80::64f0:273b:28a6:72b9/128
                                    On-link
 14    276 fe80::f94d:9dfa:c394:9f82/128
                                    On-link
  1    306 ff00::/8                 On-link
 14    276 ff00::/8                 On-link
 13    266 ff00::/8                 On-link
 15    266 ff00::/8                 On-link
===========================================================================
Persistent Routes:
  None

C:\Windows\system32>

Please advise.

2 Answers 2

1

As far as I know, the receiving interface will ignore traffic that does not match its IP, even if another interface does have a matching IP. You are expecting the server to act like it is a router, but windows will not route packets from one interface to another without enabling routing and remote access (or network sharing). I'm not sure if enabling RRAS will solve this problem, but if it did then you will likely have to enable a bunch of firewall rules to prevent any potential unwanted routing.

2

You shouldn't need a route for this at all, since you want the traffic to remain within that private subnet for this kind of communication. Just address each server you wish to interact with directly via its private IP, rather than using the public interface at all, or using names.

1
  • I explicitly wanted to use the public IP
    – nl-x
    Sep 1, 2016 at 5:48

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