Azure Site-to-Site VPN works, but RDP/Server Manager/Replication does not.

Question

Hi,
At home, I have a Raspberry Pi with Raspbian as OS. I have installed OpenSwan to make a Site-to-Site VPN between the Raspberry and Azure. The Raspberry has an IP Address of 192.168.1.2 behind NAT. Ping works from both sites, but I'm not able to RDP or for
example manage the servers within the Server Manager. The AD Replication doesn't work either, but I was able to join a VM in Azure over this VPN. I'm using the following configuration:
Network topology:
• 192.168.1.0/24 - Home network
• 192.168.2.0/24 - Azure network
• 192.168.1.1 - Home router's private IP
• 192.168.1.2 - Raspberry Pi
I enabled L2TP Passthrough in the router firewall and I tried to forward the following ports to my RPI:
• UDP 500
• UDP 4500
I also tried to place the Pi in the DMZ.
My ipsec.conf looks like this:
version 2.0
config setup
    nat_traversal=yes
    virtual_private=%4:192.168.1.0/24
    protostack=auto
    interfaces="ipsec0=eth0"
conn azure
    authby=secret
    auto=start
    type=tunnel
    left=192.168.1.2
    leftsubnet=192.168.1.0/24
    leftnexthop=192.168.1.1
    right=[Azure IP]
    rightsubnet=192.168.2.0/24
    ike=3des-sha1-modp1024,aes128-sha1-modp1024
    esp=3des-sha1,aes128-sha1
    pfs=no
ipsec.secrets:
192.168.1.2 [Azure IP] : PSK "AzureSecret"
That got the link up and running, to allow routing between sites:
/etc/sysctl.conf:
net.ipv4.ip_forward = 1
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.rp_filter = 0
net.ipv4.conf.default.accept_source_route = 0
net.ipv4.conf.default.send_redirects = 0
net.ipv4.icmp_ignore_bogus_error_responses = 1
IPtables rules:
iptables -A FORWARD -s 192.168.2.0/24 -m policy --dir in --pol ipsec -j ACCEPT
iptables -A FORWARD -s 192.168.1.0/24 -m policy --dir out --pol ipsec -j ACCEPT
iptables -A INPUT -p udp -m udp --dport 500 -j ACCEPT
iptables -A INPUT -p udp -m udp --dport 4500 -j ACCEPT
iptables -A INPUT -m policy --dir in --pol ipsec -j ACCEPT
iptables -A INPUT -p esp -j ACCEPT
The NAT table allows the Azure VM's to connect to any machine on my home network:
iptables -A PREROUTING –t nat -i eth0 -p udp -m udp --dport 4500 -j DNAT --to-destination [Azure IP]:4500
iptables -A PREROUTING –t nat -i eth0 -p udp -m udp --dport 500 -j DNAT --to-destination [Azure IP]:500
iptables –t nat -A POSTROUTING -o eth0 -j MASQUERADE
With all this I can ping and communicate in both directions, all Azure VM's can see my home network, all home network machines can see my Azure VM's.
Any idea what's going wrong? Thank you!

Answer 1

Hi Arvind,
I can confirm that RDP from the server in Azure works to my home lab. It doesn't work from my home lab (DC01) to Azure (DC02-1). I did a capture on my DC01 with NetMon.
DC01 is 192.168.1.10 (home)
DC02-1 is 192.168.2.4 (Azure)
I found the following 'errors' in the capture:
- Scale factor not supported
- Checksum: 0x9EBF, Disregarded
Do you know what's the problem?
Take a look at the capture below:
215 11:24:20 27-12-2014 1.8730574 mstsc.exe 192.168.1.10 192.168.2.4 TCP TCP:Flags=CE....S., SrcPort=50487, DstPort=MS WBT Server(3389), PayloadLen=0, Seq=4073688143, Ack=0, Win=8192 ( Negotiating scale factor 0x8 ) = 8192 {TCP:5, IPv4:11}
222 11:24:20 27-12-2014 1.9105602 mstsc.exe 192.168.2.4 192.168.1.10 TCP TCP:Flags=.E.A..S., SrcPort=MS WBT Server(3389), DstPort=50487, PayloadLen=0, Seq=3665192609, Ack=4073688144, Win=64000 ( Scale factor not supported ) = 64000 {TCP:5, IPv4:11}
223 11:24:20 27-12-2014 1.9106166 mstsc.exe 192.168.1.10 192.168.2.4 TCP TCP:Flags=...A...., SrcPort=50487, DstPort=MS WBT Server(3389), PayloadLen=0, Seq=4073688144, Ack=3665192610, Win=515 (scale factor 0x8) = 131840 {TCP:5, IPv4:11}
224 11:24:20 27-12-2014 1.9118241 mstsc.exe 192.168.1.10 192.168.2.4 RDP RDP:Windows stub parser: Requires full Common parsers. See the "How Do I Change Parser Set Options(Version 3.3 or before) or Configure Parser Profile (Version 3.4)" help topic for tips on loading these parser sets. {TCP:5, IPv4:11}
236 11:24:20 27-12-2014 2.2214169 mstsc.exe 192.168.1.10 192.168.2.4 TCP TCP:[ReTransmit #224]Flags=...AP..., SrcPort=50487, DstPort=MS WBT Server(3389), PayloadLen=19, Seq=4073688144 - 4073688163, Ack=3665192610, Win=515 (scale factor 0x8) = 131840 {TCP:5, IPv4:11}
262 11:24:21 27-12-2014 2.8307052 mstsc.exe 192.168.1.10 192.168.2.4 TCP TCP:[ReTransmit #224]Flags=...AP..., SrcPort=50487, DstPort=MS WBT Server(3389), PayloadLen=19, Seq=4073688144 - 4073688163, Ack=3665192610, Win=515 (scale factor 0x8) = 131840 {TCP:5, IPv4:11}
338 11:24:22 27-12-2014 4.0339011 mstsc.exe 192.168.1.10 192.168.2.4 TCP TCP:[ReTransmit #224]Flags=...AP..., SrcPort=50487, DstPort=MS WBT Server(3389), PayloadLen=19, Seq=4073688144 - 4073688163, Ack=3665192610, Win=515 (scale factor 0x8) = 131840 {TCP:5, IPv4:11}
370 11:24:23 27-12-2014 4.9156751 mstsc.exe 192.168.2.4 192.168.1.10 TCP TCP:Flags=.E.A..S., SrcPort=MS WBT Server(3389), DstPort=50487, PayloadLen=0, Seq=3665192609, Ack=4073688144, Win=64000 ( Scale factor not supported ) = 64000 {TCP:5, IPv4:11}
371 11:24:23 27-12-2014 4.9157253 mstsc.exe 192.168.1.10 192.168.2.4 TCP TCP:Flags=...A...., SrcPort=50487, DstPort=MS WBT Server(3389), PayloadLen=0, Seq=4073688163, Ack=3665192610, Win=515 (scale factor 0x8) = 131840 {TCP:5, IPv4:11}
383 11:24:23 27-12-2014 5.2369090 mstsc.exe 192.168.1.10 192.168.2.4 TCP TCP:[ReTransmit #224]Flags=...AP..., SrcPort=50487, DstPort=MS WBT Server(3389), PayloadLen=19, Seq=4073688144 - 4073688163, Ack=3665192610, Win=515 (scale factor 0x8) = 131840 {TCP:5, IPv4:11}
429 11:24:25 27-12-2014 6.4450070 mstsc.exe 192.168.1.10 192.168.2.4 TCP TCP:[ReTransmit #224]Flags=...AP..., SrcPort=50487, DstPort=MS WBT Server(3389), PayloadLen=19, Seq=4073688144 - 4073688163, Ack=3665192610, Win=515 (scale factor 0x8) = 131840 {TCP:5, IPv4:11}
520 11:24:27 27-12-2014 8.8541736 mstsc.exe 192.168.1.10 192.168.2.4 TCP TCP:[ReTransmit #224]Flags=...AP..., SrcPort=50487, DstPort=MS WBT Server(3389), PayloadLen=19, Seq=4073688144 - 4073688163, Ack=3665192610, Win=515 (scale factor 0x8) = 131840 {TCP:5, IPv4:11}
587 11:24:29 27-12-2014 10.9267084 mstsc.exe 192.168.2.4 192.168.1.10 TCP TCP:Flags=...A..S., SrcPort=MS WBT Server(3389), DstPort=50487, PayloadLen=0, Seq=3665192609, Ack=4073688144, Win=64000 ( Scale factor not supported ) = 64000 {TCP:5, IPv4:11}
Frame: Number = 587, Captured Frame Length = 62, MediaType = ETHERNET
+ Ethernet: Etype = Internet IP (IPv4),DestinationAddress:[MAC Address],SourceAddress:[B8-27-EB-8C-CA-84]
+ Ipv4: Src = 192.168.2.4, Dest = 192.168.1.10, Next Protocol = TCP, Packet ID = 17414, Total IP Length = 48
- Tcp: Flags=...A..S., SrcPort=MS WBT Server(3389), DstPort=50487, PayloadLen=0, Seq=3665192609, Ack=4073688144, Win=64000 ( Scale factor not supported ) = 64000
SrcPort: MS WBT Server(3389)
DstPort: 50487
SequenceNumber: 3665192609 (0xDA7666A1)
AcknowledgementNumber: 4073688144 (0xF2CF8C50)
+ DataOffset: 112 (0x70)
+ Flags: ...A..S.
Window: 64000 ( Scale factor not supported ) = 64000
Checksum: 0x57F9, Good
UrgentPointer: 0 (0x0)
+ TCPOptions:
588 11:24:29 27-12-2014 10.9267808 mstsc.exe 192.168.1.10 192.168.2.4 TCP TCP:[Dup Ack #371]Flags=...A...., SrcPort=50487, DstPort=MS WBT Server(3389), PayloadLen=0, Seq=4073688163, Ack=3665192610, Win=515 (scale factor 0x8) = 131840 {TCP:5, IPv4:11}
698 11:24:32 27-12-2014 13.6755119 mstsc.exe 192.168.1.10 192.168.2.4 TCP TCP:[ReTransmit #224]Flags=...AP..., SrcPort=50487, DstPort=MS WBT Server(3389), PayloadLen=19, Seq=4073688144 - 4073688163, Ack=3665192610, Win=515 (scale factor 0x8) = 131840 {TCP:5, IPv4:11}
Frame: Number = 698, Captured Frame Length = 73, MediaType = ETHERNET
+ Ethernet: Etype = Internet IP (IPv4),DestinationAddress:[MAC Address],SourceAddress:[MAC Address]
+ Ipv4: Src = 192.168.1.10, Dest = 192.168.2.4, Next Protocol = TCP, Packet ID = 17408, Total IP Length = 59
- Tcp: [ReTransmit #224]Flags=...AP..., SrcPort=50487, DstPort=MS WBT Server(3389), PayloadLen=19, Seq=4073688144 - 4073688163, Ack=3665192610, Win=515 (scale factor 0x8) = 131840
SrcPort: 50487
DstPort: MS WBT Server(3389)
SequenceNumber: 4073688144 (0xF2CF8C50)
AcknowledgementNumber: 3665192610 (0xDA7666A2)
+ DataOffset: 80 (0x50)
+ Flags: ...AP...
Window: 515 (scale factor 0x8) = 131840
Checksum: 0x9EBF, Disregarded
UrgentPointer: 0 (0x0)
RetransmitPayload: Binary Large Object (19 Bytes)
722 11:24:32 27-12-2014 14.3901288 mstsc.exe 192.168.1.10 192.168.2.4 TCP TCP:Flags=C..A.R.., SrcPort=50487, DstPort=MS WBT Server(3389), PayloadLen=0, Seq=4073688163, Ack=3665192610, Win=0 (scale factor 0x8) = 0 {TCP:5, IPv4:11}