Cluster LVS-NAT

1. Cluster classification
*
Load balancing cluster: such as nginx (solving high concurrency)
*
High-availability cluster: such as MHA, MMM
*
High-performance cluster, using more computing services

2. Load balancing cluster

* LVS：linux virtual service  （linux虚拟服务）

3. The difference between nginx and LVS
*
nginx:

	* 

Do 7-layer load, four-layer load can also be done through the module
*
Only load balance for web and mail
*
LVS:

	* 

Do 4-layer load, forwarding traffic to achieve load balancing
*
You can do load balancing for any service, such as mysql load balancing can’t use nginx, you can use lvs

4. LVS working mode
*
NAT: address translation
*
DR: direct routing
*
TUN: IP tunnel
*
FULL-NAT
*
ENT

ps:
*
SNAT: source IP
*
DNAT: destination IP

5. LVS scheduling algorithm
*
rr: round-robin
*
wrr: weighted round-robin
*
lc: minimum connection (allocate to whomever has the least number of connections)
*
wlc: weighted minimum link (distribute connections in proportion)
*
blc, blcr, dh, sh, sed, nq

6. LVS-NAT is to use DNAT mode
*
Advantages: Security, all requests go through the LVS server
*
Disadvantages: LVS is under pressure

7. modprobe loads the kernel module
*
modprobe ip_vs
*
lsmod | grep ip_vs view
*
cat /proc/modules | grep ip_vs view

8. ipvsadm option
*
-A: specify virtual server address (vip)
*
-a: add real server
*
-E: edit virtual server
*
-D: delete virtual server
*
-s: specify scheduling algorithm (rr, wrr, lc, wlc, blc, blcr, dh, sh, sed, nq)
*
-w: designated weight
*
-g: designated mode DR
*
-i: designated mode TUN
*
-m: designated mode NAT
*
-r: designated real server address
*
-t: tcp protocol
*
-u: udp protocol
*
-c: connection status display

9. LVS-NAT implementation key points:
*
LVS server has dual network cards, internal network and external network
* The
gateway address of the real server points to the address of the LVS internal network card

10. The concrete realization of LVS-NAT

1. Need three servers, one LVS host, two apache
2. First, configure the network card of the two apache hosts to host-
   only mode, then power on and modify the network card configuration file
   vim /etc/sysconfig/network-scripts/ifcfg-ens33.
   
   Note that the gateway address needs to be set to the LVS internal network card IP. Second An apache host also performs copper sleeve operations.
3. Modify the LVS server network
   card. One network card is the host only (internal network IP), and the other is in bridge mode (external network).
   
4. Install httpd service on two apache machines
   [root@apache1 ~]# yum -y install httpd
   [root@apache1 ~]# systemctl start httpd
   [root@apache1 ~]# echo “apache111111”> /var/www/html/index. html
   [root@apache2 ~]# echo "apache22222222"> /var/www/html/index.htmlAccess
   test
   
   
5. LVS host install ipvsadm

[root@lvs ~]# yum -y install ipvsadm
[root@lvs ~]# ipvsadm -A -t 192.168.10.74:80 -s rr   //设置虚拟服务
[root@lvs ~]# ipvsadm -a -t 192.168.10.74:80 -r 192.168.8.20:80 -m -w 1  //添加地址转换
[root@lvs ~]# ipvsadm -a -t 192.168.10.74:80 -r 192.168.8.21:80 -m -w 1  //添加地址转换

Note: In CentOS7, restarting the ipvsadm service will report an error, and restarting the service after the rule is created will cause loss.
The method to solve the above problems:

ipvsadm -s > /etc/sysconfig/ipvsadm
servicectl restart ipvsadm 成功。

[root@lvs ~]# ipvsadm -l -n   //查看设置的规则

6. Enable routing and forwarding function

[root@lvs ~]# vim /etc/sysctl.conf
net.ipv4.ip_forward = 1

sysctl -p view

7. Access test
   
   

[root@lvs ~]# ipvsadm -L -c -n    //查看连接状态