TCP Load Balancing Using Destination NAT

admin

2 years ago

We will use ip nat inside destination command to split up the load from what looks one global destination , to several inside hosts. This is similar like server load balancing, at least without all the health checks.
Below is our topology:

Using only two links just to show the flexibility of this configuration.

We have static default routes from R1, R2, and R3 pointing to R4.

Below is the R4 configuration:

interface FastEthernet0/0
ip address 192.168.0.4 255.255.255.0
ip nat inside
ip virtual-reassembly
!
interface Serial1/0
ip address 192.168.45.4 255.255.255.0
ip verify unicast reverse-path
ip nat outside
ip virtual-reassembly
serial restart-delay 0
!
interface Serial1/1
ip address 192.168.46.4 255.255.255.0
ip verify unicast reverse-path
ip nat outside
ip virtual-reassembly
!
ip route 0.0.0.0 0.0.0.0 192.168.45.5
ip route 0.0.0.0 0.0.0.0 192.168.46.6
!
ip nat pool POOL 192.168.0.1 192.168.0.3 prefix-length 24 type rotary
ip nat inside destination list 10 pool POOL
!
access-list 10 permit 192.168.45.10
access-list 10 permit 192.168.46.10

Verifying from R7:

R7#telnet 192.168.45.10 
Trying 192.168.45.10 ... Open

R1>
R1>exit

[Connection to 192.168.45.10 closed by foreign host]
R7#telnet 192.168.45.10
Trying 192.168.45.10 ... Open

R2>exit

[Connection to 192.168.45.10 closed by foreign host]
R7#telnet 192.168.45.10
Trying 192.168.45.10 ... Open

R3>exit

[Connection to 192.168.45.10 closed by foreign host]
R7#telnet 192.168.46.10
Trying 192.168.46.10 ... Open

R1>exit

[Connection to 192.168.46.10 closed by foreign host]
R7#telnet 192.168.46.10
Trying 192.168.46.10 ... Open

R2>exit

[Connection to 192.168.46.10 closed by foreign host]
R7#

NAT table on R4:

R4#sho ip nat translations
Pro Inside global      Inside local       Outside local      Outside global
tcp 192.168.45.10:23   192.168.0.1:23     200.0.0.7:51519    200.0.0.7:51519
tcp 192.168.46.10:23   192.168.0.1:23     200.0.0.7:64139    200.0.0.7:64139
tcp 192.168.46.10:23   192.168.0.2:23     200.0.0.7:11691    200.0.0.7:11691
tcp 192.168.45.10:23   192.168.0.2:23     200.0.0.7:62913    200.0.0.7:62913
tcp 192.168.45.10:23   192.168.0.3:23     200.0.0.7:17295    200.0.0.7:17295

Thanks for reading blog ……….

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