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Re: NAT Network and RHEL 7 network setup
Posted: 25. Jul 2019, 12:16
by fth0
socratis wrote:Networking question for you: assume that I have two VMs, or even better Computers with public IP addresses (like 198.168.4.x), but in a LAN-like environment, and let's go with the simplest case; Ethernet cable to the router. Wouldn't the fact that they're in the same masked range (255.255.255.0) mean that the packets wouldn't go through the router to the outside world, but the router (knowing the arp table) simply forward the packets to the corresponding destination?
Yes, the packets wouldn't go to the outside world. But even your simple scenario may be a little bit more complex as you think by now:
1. If a
router device has multiple Ethernet ports, in reality it consists of an
integrated Ethernet switch and a
router, and the router is internally connected to an invisible switch port. In consequence, the router doesn't automatically 'see' all traffic going through the internal switch (like in the case with an external switch device). However, the router has access to the ARP cache of the switch.
2. In the simplest case, the router will only see the ARP requests (Ethernet broadcast frames), but neither the local ARP replies (Ethernet unicast frames) nor the IPv4 packets. The router itself will not even answer the ARP requests, despite knowing the answer. (Unless configured for Proxy ARP, which is normally used for more complex scenarios like road warriors.)
In the NAT networking case however, the router usually has no knowledge of the IPv4 addresses of the NAT network. If an IPv4 packet reaches the router (because of it's gateway functionality), then the IPv4 destination address is searched for in the routing table, which usually contains (amongst others) the configured local networks, the blocking routes for the private IPv4 address ranges, and a default route to the Internet ...
Re: NAT Network and RHEL 7 network setup
Posted: 1. Sep 2019, 11:14
by EddyR
All.
Sorry for the delay as I was taken off onto different projects.
All the comments re OCR, etc., are correct so I went back and formalized the question (screenshots are available).
Issue: I'm using Oracle VirtualBox on Windows 10 with the default installation. When I create a brand new Linux VM (CentOS/Red Hat) using the NAT Network that I have defined which provides DHCP service, I receive a default IP address in a different subnet. I expected to get an IP address in the subnet that I defined in the NatNetwork CIDR.
Specifics:
• NatNetwork defined with CIDR 192.168.4.0/24
• CentOS – as an example – defined to use DHCP
• After new install I expect to get an IP address from DHCP in the subnet 192.168.0 but in fact I get an IP in 198.168.4.0
NOTE that the default GW is defined correctly (192.168.4.1)
• If I setup the IP interface correctly then I can automatically ping the gateway and the outside world as expected, as well as other VMs in that subnet (which is the definition of the NAT Network)
To get rid of the 198.168.4.0 address I need to edit /etc/sysconfig/network-scripts/ifcfg-eth0 and change BOOTPROTO=none followed by
# nmcli connection up eth0
Environment details:
Oracle VirtualBox: Version 6.0.10 r132072 (Qt5.6.2)
Windows 10 Enterprise
Re: NAT Network and RHEL 7 network setup
Posted: 1. Sep 2019, 11:22
by socratis
EddyR wrote:NatNetwork defined with CIDR 192.168.4.0/24 ... I expect to get an IP address from DHCP in the subnet 192.168.0
Why would you expect that? If you have defined a specific IP range for you DHCP server,
expect an IP from that range. Not a random thing...
Re: NAT Network and RHEL 7 network setup
Posted: 1. Sep 2019, 12:32
by fth0
Additional questions: What is the network configuration of the host? Can you provide us with the output of 'ipconfig /all' and 'route print' from the host?
Re: NAT Network and RHEL 7 network setup
Posted: 2. Sep 2019, 09:19
by EddyR
Another typo of mine - of course I'd expect an IP in the range of 192.168.4 but I get one in the range of 198.162.4
Have you tried this on your installation and get the correct IP from DHCP?
Re output from the host:
Code: Select all
T:\>ipconfig
Windows IP Configuration
Ethernet adapter Local Area Connection* 3:
Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Ethernet adapter Ethernet:
Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . : Home
Ethernet adapter vEthernet (Default Switch):
Connection-specific DNS Suffix . :
Link-local IPv6 Address . . . . . : fe80::d9c1:14e1:9784:b03b%3
IPv4 Address. . . . . . . . . . . : 172.21.52.1
Subnet Mask . . . . . . . . . . . : 255.255.255.240
Default Gateway . . . . . . . . . :
Ethernet adapter vEthernet (DockerNAT):
Connection-specific DNS Suffix . :
Link-local IPv6 Address . . . . . : fe80::502:8751:d6bd:d05b%26
IPv4 Address. . . . . . . . . . . : 10.0.75.1
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . :
Ethernet adapter VirtualBox Host-Only Network:
Connection-specific DNS Suffix . :
Link-local IPv6 Address . . . . . : fe80::4875:67df:74bb:b43f%8
IPv4 Address. . . . . . . . . . . : 192.168.56.1
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . :
Ethernet adapter Ethernet 4:
Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Wireless LAN adapter Local Area Connection* 1:
Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Wireless LAN adapter Local Area Connection* 2:
Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Ethernet adapter Ethernet 2:
Connection-specific DNS Suffix . : bynet.co.il
Link-local IPv6 Address . . . . . : fe80::b4b9:2d35:372f:c8b0%20
IPv4 Address. . . . . . . . . . . : 10.101.0.141
Subnet Mask . . . . . . . . . . . : 255.255.0.0
Default Gateway . . . . . . . . . : 10.101.254.254
Ethernet adapter Bluetooth Network Connection:
Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Wireless LAN adapter Wi-Fi:
Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . : Home
PPP adapter Umbrella:
Connection-specific DNS Suffix . :
IPv4 Address. . . . . . . . . . . : 100.122.139.216
Subnet Mask . . . . . . . . . . . : 255.255.255.255
Default Gateway . . . . . . . . . :
T:\>route print
===========================================================================
Interface List
9...00 ff b0 8b 52 6d ......Juniper Network Connect Virtual Adapter
21...e4 b9 7a 40 21 19 ......Intel(R) Ethernet Connection (4) I219-LM
3...c2 15 e6 46 8a 4c ......Hyper-V Virtual Ethernet Adapter
26...00 15 5d 81 1b 04 ......Hyper-V Virtual Ethernet Adapter #2
8...0a 00 27 00 00 08 ......VirtualBox Host-Only Ethernet Adapter
5...54 61 be 0d 97 18 ......Check Point Virtual Network Adapter For Endpoint VPN Client
18...64 5d 86 c6 8f d2 ......Microsoft Wi-Fi Direct Virtual Adapter
23...66 5d 86 c6 8f d1 ......Microsoft Wi-Fi Direct Virtual Adapter #2
20...e4 b9 7a c2 65 ea ......Realtek USB GbE Family Controller
16...64 5d 86 c6 8f d5 ......Bluetooth Device (Personal Area Network)
12...64 5d 86 c6 8f d1 ......Intel(R) Dual Band Wireless-AC 8265
1...........................Software Loopback Interface 1
101...........................Umbrella
===========================================================================
IPv4 Route Table
===========================================================================
Active Routes:
Network Destination Netmask Gateway Interface Metric
0.0.0.0 0.0.0.0 10.101.254.254 10.101.0.141 35
2.17.34.39 255.255.255.255 On-link 100.122.139.216 600
2.17.102.118 255.255.255.255 On-link 100.122.139.216 600
5.62.48.218 255.255.255.255 On-link 100.122.139.216 600
10.0.75.0 255.255.255.0 On-link 10.0.75.1 271
10.0.75.1 255.255.255.255 On-link 10.0.75.1 271
10.0.75.255 255.255.255.255 On-link 10.0.75.1 271
10.101.0.0 255.255.0.0 On-link 10.101.0.141 291
10.101.0.141 255.255.255.255 On-link 10.101.0.141 291
10.101.255.255 255.255.255.255 On-link 10.101.0.141 291
14.215.158.100 255.255.255.255 On-link 100.122.139.216 600
23.4.43.27 255.255.255.255 On-link 100.122.139.216 600
23.41.177.70 255.255.255.255 On-link 100.122.139.216 600
23.108.191.211 255.255.255.255 On-link 100.122.139.216 600
23.212.54.230 255.255.255.255 On-link 100.122.139.216 600
37.220.39.62 255.255.255.255 On-link 100.122.139.216 600
37.252.232.102 255.255.255.255 On-link 100.122.139.216 600
61.151.165.101 255.255.255.255 On-link 100.122.139.216 600
61.151.165.102 255.255.255.255 On-link 100.122.139.216 600
62.8.79.10 255.255.255.255 On-link 100.122.139.216 600
62.138.209.134 255.255.255.255 On-link 100.122.139.216 600
62.138.209.148 255.255.255.255 On-link 100.122.139.216 600
62.138.209.160 255.255.255.255 On-link 100.122.139.216 600
62.138.209.164 255.255.255.255 On-link 100.122.139.216 600
62.138.209.170 255.255.255.255 On-link 100.122.139.216 600
67.215.68.253 255.255.255.255 On-link 100.122.139.216 600
67.215.70.91 255.255.255.255 On-link 100.122.139.216 600
67.227.226.240 255.255.255.255 On-link 100.122.139.216 600
69.22.151.220 255.255.255.255 On-link 100.122.139.216 600
69.22.151.221 255.255.255.255 On-link 100.122.139.216 600
69.192.2.132 255.255.255.255 On-link 100.122.139.216 600
69.192.2.137 255.255.255.255 On-link 100.122.139.216 600
72.52.179.175 255.255.255.255 On-link 100.122.139.216 600
74.125.68.138 255.255.255.255 On-link 100.122.139.216 600
80.231.123.131 255.255.255.255 On-link 100.122.139.216 600
92.123.65.126 255.255.255.255 On-link 100.122.139.216 600
92.242.140.2 255.255.255.255 On-link 100.122.139.216 600
94.136.40.51 255.255.255.255 On-link 100.122.139.216 600
95.101.30.97 255.255.255.255 On-link 100.122.139.216 600
100.122.139.216 255.255.255.255 On-link 100.122.139.216 756
101.89.15.100 255.255.255.255 On-link 100.122.139.216 600
101.226.49.141 255.255.255.255 On-link 100.122.139.216 600
101.226.49.144 255.255.255.255 On-link 100.122.139.216 600
113.96.209.108 255.255.255.255 On-link 100.122.139.216 600
113.219.145.1 255.255.255.255 On-link 100.122.139.216 600
127.0.0.0 255.0.0.0 On-link 127.0.0.1 331
127.0.0.1 255.255.255.255 On-link 127.0.0.1 331
127.255.255.255 255.255.255.255 On-link 127.0.0.1 331
134.170.3.182 255.255.255.255 On-link 100.122.139.216 600
146.112.62.40 255.255.255.255 On-link 100.122.139.216 600
149.36.228.3 255.255.255.255 On-link 100.122.139.216 600
149.36.228.6 255.255.255.255 On-link 100.122.139.216 600
154.73.75.130 255.255.255.255 On-link 100.122.139.216 600
154.73.75.132 255.255.255.255 On-link 100.122.139.216 600
157.185.169.223 255.255.255.255 On-link 100.122.139.216 600
157.185.177.206 255.255.255.255 On-link 100.122.139.216 600
157.240.16.35 255.255.255.255 On-link 100.122.139.216 600
172.21.52.0 255.255.255.240 On-link 172.21.52.1 271
172.21.52.1 255.255.255.255 On-link 172.21.52.1 271
172.21.52.15 255.255.255.255 On-link 172.21.52.1 271
172.217.21.162 255.255.255.255 On-link 100.122.139.216 600
172.217.194.147 255.255.255.255 On-link 100.122.139.216 600
178.132.201.156 255.255.255.255 On-link 100.122.139.216 600
178.255.155.178 255.255.255.255 On-link 100.122.139.216 600
179.185.45.21 255.255.255.255 On-link 100.122.139.216 600
183.3.234.11 255.255.255.255 On-link 100.122.139.216 600
183.192.169.103 255.255.255.255 On-link 100.122.139.216 600
183.236.60.129 255.255.255.255 On-link 100.122.139.216 600
188.172.192.101 255.255.255.255 On-link 100.122.139.216 600
188.172.198.140 255.255.255.255 On-link 100.122.139.216 600
192.30.253.112 255.255.255.255 On-link 100.122.139.216 600
192.168.56.0 255.255.255.0 On-link 192.168.56.1 281
192.168.56.1 255.255.255.255 On-link 192.168.56.1 281
192.168.56.255 255.255.255.255 On-link 192.168.56.1 281
195.244.97.198 255.255.255.255 On-link 100.122.139.216 600
195.244.97.214 255.255.255.255 On-link 100.122.139.216 600
195.244.97.218 255.255.255.255 On-link 100.122.139.216 600
195.244.97.222 255.255.255.255 On-link 100.122.139.216 600
195.244.97.228 255.255.255.255 On-link 100.122.139.216 600
195.244.97.230 255.255.255.255 On-link 100.122.139.216 600
195.244.97.234 255.255.255.255 On-link 100.122.139.216 600
199.59.242.151 255.255.255.255 On-link 100.122.139.216 600
203.205.146.17 255.255.255.255 On-link 100.122.139.216 600
203.205.151.204 255.255.255.255 On-link 100.122.139.216 600
203.205.158.67 255.255.255.255 On-link 100.122.139.216 600
203.205.219.196 255.255.255.255 On-link 100.122.139.216 600
203.205.255.143 255.255.255.255 On-link 100.122.139.216 600
208.69.35.24 255.255.255.255 10.101.254.254 10.101.0.141 36
208.87.239.202 255.255.255.255 On-link 100.122.139.216 600
209.107.220.190 255.255.255.255 On-link 100.122.139.216 600
209.170.97.239 255.255.255.255 On-link 100.122.139.216 600
213.131.255.22 255.255.255.255 On-link 100.122.139.216 600
213.131.255.24 255.255.255.255 On-link 100.122.139.216 600
213.131.255.28 255.255.255.255 On-link 100.122.139.216 600
213.186.33.17 255.255.255.255 On-link 100.122.139.216 600
213.227.185.136 255.255.255.255 On-link 100.122.139.216 600
222.165.175.38 255.255.255.255 On-link 100.122.139.216 600
222.165.175.166 255.255.255.255 On-link 100.122.139.216 600
224.0.0.0 240.0.0.0 On-link 127.0.0.1 331
224.0.0.0 240.0.0.0 On-link 192.168.56.1 281
224.0.0.0 240.0.0.0 On-link 10.0.75.1 271
224.0.0.0 240.0.0.0 On-link 172.21.52.1 271
224.0.0.0 240.0.0.0 On-link 10.101.0.141 291
224.0.0.0 240.0.0.0 On-link 100.122.139.216 756
255.255.255.255 255.255.255.255 On-link 127.0.0.1 331
255.255.255.255 255.255.255.255 On-link 192.168.56.1 281
255.255.255.255 255.255.255.255 On-link 10.0.75.1 271
255.255.255.255 255.255.255.255 On-link 172.21.52.1 271
255.255.255.255 255.255.255.255 On-link 10.101.0.141 291
255.255.255.255 255.255.255.255 On-link 100.122.139.216 756
===========================================================================
Persistent Routes:
None
IPv6 Route Table
===========================================================================
Active Routes:
If Metric Network Destination Gateway
1 331 ::1/128 On-link
8 281 fe80::/64 On-link
26 271 fe80::/64 On-link
3 271 fe80::/64 On-link
20 291 fe80::/64 On-link
26 271 fe80::502:8751:d6bd:d05b/128
On-link
8 281 fe80::4875:67df:74bb:b43f/128
On-link
20 291 fe80::b4b9:2d35:372f:c8b0/128
On-link
3 271 fe80::d9c1:14e1:9784:b03b/128
On-link
1 331 ff00::/8 On-link
8 281 ff00::/8 On-link
26 271 ff00::/8 On-link
3 271 ff00::/8 On-link
20 291 ff00::/8 On-link
===========================================================================
Persistent Routes:
None
Re: NAT Network and RHEL 7 network setup
Posted: 2. Sep 2019, 10:48
by fth0
EddyR wrote:Re output from the host: [...]
A lot of different networks. But I see nothing that should interfere with your NAT network.
EddyR wrote:Another typo of mine - of course I'd expect an IP in the range of 192.168.4 but I get one in the range of 198.162.4
Yet another typo of yours (the part I underlined)? As long as you intermix 192, 198, 168 and 162, which of your given information am I supposed to believe and which not?
If I were you, I would only use private IP address ranges in local networks (like the NAT network). From those 4 numbers, only the 192.168.x.y combination would qualify.
Re: NAT Network and RHEL 7 network setup
Posted: 2. Sep 2019, 14:13
by EddyR
You're right again - my typo.
My CIDR is 192.162.4.0/24
The VM get 198.162.4.x from the VB's DHCP server - this is incorrect and not as documented.
Do you experience something different in your own setup?
If not, why is my VB acting in this fashion?
Re: NAT Network and RHEL 7 network setup
Posted: 2. Sep 2019, 18:06
by socratis
EddyR wrote:Do you experience something different in your own setup?
Yes, everything is working fine on 99.99% of the cases. You're the 0.01%.
EddyR wrote:If not, why is my VB acting in this fashion?
No clue if it's in reality VirtualBox at this point...
Re: NAT Network and RHEL 7 network setup
Posted: 3. Sep 2019, 15:43
by EddyR
Why wouldn't this work for all cases?
What would make this not work?
Re: NAT Network and RHEL 7 network setup
Posted: 4. Sep 2019, 23:42
by socratis
EddyR wrote:Why wouldn't this work for all cases?
Because it depends on the guest configuration, and you might have done something in there. What exactly? I don't have the slightest idea. But most certainly this doesn't look like a VirtualBox issue.
EddyR wrote:What would make this not work?
Start from scratch. Or figure out what's going on with your guest. We can't do that from here...