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Forrestrun
Website System Engineers and Architects
June 2004
This article discusses how to use VMware to simulate multiple computers on a single computer and achieve the networking of multiple simulated machines in a complex network environment, the following uses zebra routing software and IPv6 as an example to test and describe it.
Why is this test required?
VMware makes sense for software developers and network maintenance personnel. It is not only because it can easily and concisely simulate a virtual machine environment for work, but also in operations that have an impact on the OS, such as network attacks and destructive experiments, if VMware is used, it will be very secure, because the impact of the virtual environment is only on a data file, and will not really cause other problems to the host hardware equipment software program. The system adjustment in the production system is not proven by test data, and the direct launch of the system rashly implies great risks, if software developers or system administrators use VMWare, such tests and research will be well suited.
In addition, many network environment tests and experiments require the use of switches (or hubs), a bunch of Network cables, and multiple test devices. When I used to conduct a network experiment with a Cisco router of the 25 series, the workload of Connecting Five Cisco routers and a bunch of Network cables was not small, and this experiment was expensive.
VMware Workstation is a virtual computer software developed by VMWare for desktop users on a single machine. With this software, you can customize multiple virtual computers to run on a real operating platform and a complex network environment based on the local conditions. Under some circumstances, you can discard the many network devices!
Another point is that there are a lot of materials to use VMWare for a single system, but the materials that focus on the virtual network environment are not very common. Here we hope to introduce them.
What is VMware?
VMware is a powerful Virtual Machine Software (http://www.vmware.com) for VMware Inc ). It has multiple versions, including gsx and ESX for servers and workstation for desktop users. We can provide a complete Ethernet environment in VMware, and even have nine vswitches available for us! For more information, see his online manual.
Lab Environment
Vro is the core device in the network. It is realistic to test and study the vro in the actual network environment. Building a complicated vro environment is costly. Using the powerful router software zebra in Linux and VMWare's virtual network, we can build our own router experiment environment and continue to expand as needed. In addition, IPv6 and other tests must use multiple network devices and use network analysis tools for analysis to better understand and learn.
1. Environment preparation:
Lab environment:
1) IBM ThinkPad r40e laptop (CPU P4 2.0g, M memory, 30 gdisk)
2) windowns XP Home Edition + SP1
3) vmware workstation 4.0.5 build-6030 + 30 days license
2. Change the Network Configuration:
After installing VMWare, I first changed the network environment of VMware (find virtual network setting in the edit menu of VMware ). The procedure is as follows:
1) Click Edit under virtual network setting... , The virtual network editor dialog box is displayed;
2) In the virtual network editor dialog box, click the button after vmnet1 in host virtual network mapping "... ", Click subnet in the pop-up menu, and then set the subnet;
3) subnet1 is set to 192.168.1.0/255.255.255.0; mnet2, vmnet3, vmnet4, vmnet8, and vmnet9 subnets are 192.168.2.0/subnet, 192.168.3.0/255.255.255.0, 192.168.4.0/255.255.255.0, 192.168.8.0/255.255.255.0, 192.168.9.0/255.255.255.0.
4) Other vmnet instances are idle. A maximum of nine subnets can be set.
3. Network customization optimization:
1) because the default installation of VMware uses IP addresses obtained through DHCP, I disabled VMware's DHCPD service after installation, and then disabled subnets to use DHCP to obtain IP addresses.
2) to allow the virtual machine to access the external network, you should set a vmnet that can use the NAT service for external access. By default, vmnet8 can access the external network through NAT. The default gateway for this subnet segment is 192.168.8.2, And the NAT service is enabled.
3) Confirm that the automatically choose an available physical network adapter to bridge to vmnet0 option of the Enable Automatic Bridge of the automatic bridging is selected.
4. Virtual Machine customization Optimization
To run multiple virtual machines on one machine, it is best to optimize each virtual machine. Based on experience, memory usage is much higher than CPU usage on virtual machines with few tasks. Therefore, we have installed the five virtual machines, namely R1, R2, R3, R4, and R5, which are based on Debian GNU/Linux. We recommend that you optimize the kernel of each virtual machine, to reduce the system overhead on the actual machine. The individual's practice is as follows:
1) Debian 3 is the simplest virtual system installed. Both the target folder and the virtual machine are named R1;
2) Add required virtual machine hardware, such as NICs;
3) Compile the bin software tool in other Debian Linux Virtual Machine environments, obtain the R1 virtual machine through SCP or FTP, and perform related configuration. I have installed some network tools such as iputils, iproute2, tcpdump, sshd, and zebra;
4) To perform IPv6 testing, compile an IPv6-supported kernel in other environments and obtain the R1 virtual;
5) Prepare for zebra: Change the. sample file to the conf file under/usr/local/ZEBRA/etc;
6) After confirming that the R1 virtual machine is ready, shut down the R1 virtual machine;
7) back up the data folder of the installation system as a permanent backup, and copy four copies named R2, R3, R4, and R5 respectively;
8) then, "Open existing virtual machines" in VMware, open the newly added four virtual machines, and change their respective vitrual machine names in option to R2, R3, respectively, r4, R5;
9) change the corresponding settings and hostname of R2, R3, R4, and R5 respectively, and change the IP address/IPv6 address accordingly.
5. Build the following network topology:
Network Configuration:
6. test:
Start the virtual machines R1 to R5 respectively, and check the connectivity of the virtual network. Check the unique virtual machine with the same network segment on each virtual machine. Take R1 as an example to perform related tests. If you want to observe the network communication process in depth, open tcpdump on the second console interface of R1 to view the information you want to observe at any time.
1) Check the NIC address ifconfig or ip command:
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2) network connectivity Ping, ping6, or arping command:
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Use of zebra routing software
1) Start zebra in the mode of running daemon, and zebra starts to listen to the local port 2602. The daemon processes of other routing protocols listen to different service ports (ripd listens to TCP port 2602 and udp520 respectively, ospfd listens on TCP 2604, bgpd listens on tcp179 and 2605, and ospf6d listens on TCP (IPv4 and IPv6) 2606 ).
2) Telnet from the PC machine to the zebra service of R1. the username and password are all zebra by default. Check whether the interface is as imaginary as the Cisco router. :)
3) Use R2, R3, R4, and R5 for routing experiments. Note: here we can not only use DEBUG of various routing software of zebra to observe the working process of the routing protocol, but also use tcpdump of Linux for more detailed observation.
4) Start zebrad and related Routing Protocol process services for each Virtual Machine (for better experiments, test each routing protocol separately );
5) Enable dynamic route discovery to see if all routers will be discovered in a moment?
In the vro mode, the network environment of the virtual machine is shown as follows:
6) We can make full use of our imagination to experiment with various routing protocols using so many "routers. If you have more ideas, such as serial port and parallel port communication, you can try again. :)
7) for more detailed use of zebra, please read the zebra manual and other materials.
Test environment of IPv6 Software
IPv6 is the next version of the IP protocol. With the development of network technology, IPv6 is becoming increasingly popular. Here is a simple IPv6 test to test the use of the new network established by VMware. We recommend that you open tcpdump-6 on the other console interfaces of the virtual machine to observe the IPv6 protocol.
1) IPv6 test preparation:
When installing the system, iproute and iputils are both tools that can test IPv6. In other Linux versions, IPv6 support modules are not loaded by default. Load each tool.
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If the IPv6 module is successfully loaded, perform the following steps:
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2) find other IPv6 devices on the network:
IPv6 no longer supports arp. Therefore, you can use the following method to find other IPv6 devices on the network in IPv6:
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Here, we use the local connection multicast address (Link-local multicast address) ff02: 1 in IPv6 to find other IPv6 devices on the same network. Fe80: 20c: 29ff: fe07: 1b34 and fe80: 20c: 29ff: fe94: 1776 belong to the IPv6 address of eth0 of R2 and eth0 of R3 respectively. (Because IPv6 is not enabled for R4, the corresponding IPv6 address of R4 cannot be seen)
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The Ping Command in IPv6 is the ping6 command in the iputil toolkit. Note that because there are multiple Nic interfaces, you must use-I to specify which Nic interface to use.
3) IPv6 routing discovered:
The IPv6 route table in the default route is as follows:
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4) Test the local IPv6 Service
Linux system currently supports IPv6 server software has been a lot, commonly used software such as opensshd/sshd, Apache, bind, telnetd, iptables-ipv6, NMAP and so on. Here we use sshd as a test.
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5) ipv6-in-ipv4 Tunnel Test
Because Ipv4 has been in the network for many years, and the development of the Internet has promoted the development of IPv4, the actual situation of IPv6 in the network is that IPv6 is like an island surrounded by the IPv4 ocean, each IPv6 network connection also needs to pass through IPv4 network, the actual common has ipv6-in-ipv4 tunnel and so on. Here we use this virtual environment for a point-to-point IPv6-in-IPv4 Tunnel Experiment (R1-R2 ).
On the R1 machine:
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On the R2 machine:
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You can also add IPv6 tunnel for R3, R4, and R5 for more complex tests.
On the R1 and R2 devices, run the ping6 command to view the IPv6 address of the Peer device;
On R1 and R2 devices, use the ssh-6 IPv6 address to log on to other IPv6 devices connected to point-to-point through IPv6 tunnel;
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OK, we have seen through ipv6-in-ipv4 tunnel that we have logged on to another device with an IPv6 address!
The tcpdump result of this process on R2:
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Summary
VMware is not just a simulated machine, but the network environment it provides is also a commendable real network. In combination with a variety of network tools, we will be able to implement the network you imagine more easily.
References
| About the author Forrestrun has been engaged in network teaching and has participated in many large-scale network projects. Currently, he is a well-known website system engineer and architect in China. He has been paying attention to TCP/IP, Linux, and Cisco network technologies. You can contact him through the forrestrun@163.com. |
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