LB旁路部署案例
一、 需求

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• 为了实现服务器对外网用户提供服务的可靠性，客户在现网中部署了LB设备，LB采用旁路方式部署，要求外网主机访问时的流量经过LB轮询到内部服务器，一台服务器down机不影响其正常业务。
  二、 拓扑环境
  
  三、 配置思路
• 配置各个设备ip地址及路由，保证ip可达
• 配置检测模板
• 配置ip地址池
• 配置实服务组，调用检测模板和ip地址池
• 配置实服务，关联实服务组
• 配置虚服务器，关联实服务组
• 测试
  四、 配置步骤
  配置脚本如下所示：
  出口NAT设备配置：

  
  sysname NAT
  #
  system-working-mode standard
  xbar load-single
  password-recovery enable
  lpu-type f-series
  #
  vlan 1
  #
  interface Serial1/0
  #
  interface Serial2/0
  #
  interface Serial3/0
  #
  interface Serial4/0
  #
  interface NULL0
  #
  interface GigabitEthernet0/0
  port link-mode route
  combo enable copper
  ip address 192.168.34.4 255.255.255.0
  #
  interface GigabitEthernet0/1
  port link-mode route
  combo enable copper
  ip address 100.1.46.4 255.255.255.0
  nat outbound
  nat server protocol tcp global 100.1.46.4 2323 inside 192.168.35.5 2323
  #
  interface GigabitEthernet0/2
  port link-mode route
  combo enable copper
  #
  interface GigabitEthernet5/0
  port link-mode route
  combo enable copper
  #
  interface GigabitEthernet5/1
  port link-mode route
  combo enable copper
  #
  interface GigabitEthernet6/0
  port link-mode route
  combo enable copper
  #
  interface GigabitEthernet6/1
  port link-mode route
  combo enable copper
  #
  scheduler logfile size 16
  #
  line class aux
  user-role network-operator
  #
  line class console
  user-role network-admin
  #
  line class tty
  user-role network-operator
  #
  line class vty
  user-role network-operator
  #
  line aux 0
  user-role network-operator
  #
  line con 0
  user-role network-admin
  #
  line vty 0 63
  user-role network-operator
  #
  ip route-static 0.0.0.0 0 100.1.46.6
  ip route-static 192.168.1.0 24 192.168.34.3
  ip route-static 192.168.2.0 24 192.168.34.3
  ip route-static 192.168.35.0 24 192.168.34.3
  #
  domain system
  #
  domain default enable system
  #
  role name level-0
  description Predefined level-0 role
  #
  role name level-1
  description Predefined level-1 role
  #
  role name level-2
  description Predefined level-2 role
  #
  role name level-3
  description Predefined level-3 role
  #
  role name level-4
  description Predefined level-4 role
  #
  role name level-5
  description Predefined level-5 role
  #
  role name level-6
  description Predefined level-6 role
  #
  role name level-7
  description Predefined level-7 role
  #
  role name level-8
  description Predefined level-8 role
  #
  role name level-9
  description Predefined level-9 role
  #              
  role name level-10
  description Predefined level-10 role
  #
  role name level-11
  description Predefined level-11 role
  #
  role name level-12
  description Predefined level-12 role
  #
  role name level-13
  description Predefined level-13 role
  #
  role name level-14
  description Predefined level-14 role
  #
  user-group system

LB关键配置：

interface GigabitEthernet1/0/1
 port link-mode route
 combo enable copper
 ip address 192.168.0.1 255.255.255.0
#
interface GigabitEthernet1/0/2
 port link-mode route
 combo enable copper
 ip address 192.168.35.5 255.255.255.0

loadbalance snat-pool pool
 ip range start 192.168.35.5 end 192.168.35.5
#
server-farm sf
 snat-pool pool
 probe t1
#
real-server rs1
 ip address 192.168.1.1
 port 23
 weight 150
 server-farm sf
#
real-server rs2
 ip address 192.168.2.2
 port 23
 weight 120    
 server-farm sf
#
virtual-server vs type tcp
 port 2323 
 virtual ip address 192.168.35.5
 default server-farm sf
 service enable
 #
 ip route-static 0.0.0.0 0 192.168.35.3
#
acl basic 2000
 rule 0 permit
security-zone name Trust
 import interface GigabitEthernet1/0/2
#
security-zone name DMZ
#
security-zone name Untrust
#
security-zone name Management
#
zone-pair security source Any destination Any
 packet-filter 2000
#
return

五、 测试
外网主机telnet外网映射到LB的地址和端口，看是否可以访问到内部服务器
telnet 100.1.46.4 2323
Trying 100.1.46.4 ...
Press CTRL+K to abort
Connected to 100.1.46.4 ...

dis ip int brief
*down: administratively down
(s): spoofing (l): loopback
Interface Physical Protocol IP Address Description
GE0/0 down down -- --
GE0/1 up up 192.168.1.1 --
测试后可以正常访问到服务器A

退出登录后再尝试登录下，测试看是否可以轮询到另一个服务器
quit

The connection was closed by the remote host!
telnet 100.1.46.4 2323
Trying 100.1.46.4 ...
Press CTRL+K to abort
Connected to 100.1.46.4 ...

dis ip int brief
*down: administratively down
(s): spoofing (l): loopback
Interface Physical Protocol IP Address Description
GE0/0 up up 192.168.2.2 --

LB>dis real-server statistics
Slot 1:
Real server: rs1
Total connections: 7
Active connections: 0
Max connections: 1
Connections per second: 0
Max connections per second: 1
Server input: 13601 bytes
Server output: 15872 bytes
Throughput: 0 bytes/s
Inbound throughput: 0 bytes/s
Outbound throughput: 0 bytes/s
Max throughput: 3612 bytes/s
Max inbound throughput: 1359 bytes/s
Max outbound throughput: 2253 bytes/s
Received packets: 252
Sent packets: 238
Dropped packets: 0
Received requests: 0
Dropped requests: 0
Sent responses: 0
Dropped responses: 0
Connection failures: 0

Real server: rs2
Total connections: 8
Active connections: 1
Max connections: 1
Connections per second: 0
Max connections per second: 1
Server input: 15552 bytes
Server output: 17213 bytes
Throughput: 0 bytes/s
Inbound throughput: 0 bytes/s
Outbound throughput: 0 bytes/s
Max throughput: 5796 bytes/s
Max inbound throughput: 2451 bytes/s
Max outbound throughput: 3345 bytes/s
Received packets: 288
Sent packets: 264
Dropped packets: 0
Received requests: 0
Dropped requests: 0
Sent responses: 0
Dropped responses: 0
Connection failures: 0

dis virtual-server statistics
Slot 1:
Virtual server: vs
Total connections: 15
Active connections: 1
Max connections: 2
Connections per second: 0
Max connections per second: 1
Client input: 29257 bytes
Client output: 33165 bytes
Throughput: 0 bytes/s
Inbound throughput: 0 bytes/s
Outbound throughput: 0 bytes/s
Max throughput: 5796 bytes/s
Max inbound throughput: 2451 bytes/s
Max outbound throughput: 3345 bytes/s
Received packets: 542
Sent packets: 504
Dropped packets: 0
六、 注意事项

• 该拓扑图中，如果只是单纯配置服务器负载均衡，不针对外网进来的源做snat的话，是无法访问到服务器的，原因是，外网终端向LB发起访问，但是数据包回复时却是内网服务器直接给予的回应，服务器回包时，数据包到核心设备，直接按照缺省路由去做转发了，即使客户端收到数据包，由于发起和回应的地址不一致，则会认为数据包不是自己想要的，会直接丢弃
• 配置LB时，新建实服务，关联实服务组，最后在虚服务器下做关联时，设备会根据检测模板去轮询看是否和服务器可达，如果可达，将处于active状态，如果检测不可达，处于Probe-failed