NAT with load-balancing

August 22, 2008 at 3:27 pm | Posted in NAT | 1 Comment

If we want telnet /http traffic from outside to a virtual IP address (or WAN IP) be load-balanced on a multiple physical servers, we can do inside destination nat translation. Normally the physical IP range is consecutive, but we can also do load-balance over non-consecutive IP range as well.

Configuration

SW1
|
|
|— R1 ——-(R3)Internet
|
|
SW2

ip nat pool SERVERS prefix-length 24 type rotary
address 10.1.1.11 10.1.1.11
address 10.1.1.22 10.1.1.22
ip nat inside destination list TELNET pool SERVERS
!
ip access-list extended TELNET
permit tcp any host 13.0.0.1 eq telnet
!

interface Serial1/1
ip address negotiated
ip nat outside

interface FastEthernet0/0
ip address 10.1.1.1 255.255.255.0
ip nat inside

Verification

R3#telnet 13.0.0.1
Trying 13.0.0.1 … Open

SW1>exit

[Connection to 13.0.0.1 closed by foreign host]
R3#telnet 13.0.0.1
Trying 13.0.0.1 … Open

SW2>exit

[Connection to 13.0.0.1 closed by foreign host]
R3#

R1#sh ip nat translation
Pro Inside global      Inside local       Outside local      Outside global
tcp 13.0.0.1:23        10.1.1.11:23       13.0.0.3:37754     13.0.0.3:37754
tcp 13.0.0.1:23        10.1.1.22:23       13.0.0.3:35071     13.0.0.3:35071

Doc CD Navigation

  • Cisco IOS IP Addressing Services Configuration Guide, Release 12.4
  • Part 6: NAT
  • Configuring NAT for IP Address Conservation
  • Configuration Examples for Configuring NAT for IP Address Conservation
  • Avoiding Server Overload Using Load Balancing: Example
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1 Comment »

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  1. Take a look here too. Slightly more descriptive than above:
    http://blogbt.net/index.php/2013/06/nat-and-nat-based-load-balancing/


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