Regarding NAT

Answered Question
Jan 27th, 2010

Hi All,

               I m facing a issue ie I have a internet connectivity from one ISP at router 1 then goes to a switch . This switch connected to other router 2 for redundant line by other ISP. Now i have done static NAT with a server IP , which is accessible from both outside and inside at router 1. Now if this first ISP link gets down then it should be accessible by other ISP but I have done NAT with first router's IP which has been provided by first ISP so i m confused that what should I do now because I cant do NAT with other IP on other router within second ISP IP range.Means this global IP should be same, it doesnt matter which ISP I m using.

Thanx and Regards,

Taran

I have this problem too.
0 votes
Correct Answer by Ganesh Hariharan about 6 years 10 months ago

Hi Ganesh,

                            Thanx for reply . So I m thinking to NAT this LAN IP with other ISP's public IP. It means I have to use 2 IPs for this . Am I right ?

thanx and regards,

Taran

Hi Taran,

Yes you need to nat with second ISP public pool ip in second isp router with the local lan private ip of the server.

Hope to help

Ganesh.H

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (1 ratings)
Loading.
Ganesh Hariharan Wed, 01/27/2010 - 00:52

Hi All,

               I m facing a issue ie I have a internet connectivity from one ISP at router 1 then goes to a switch . This switch connected to other router 2 for redundant line by other ISP. Now i have done static NAT with a server IP , which is accessible from both outside and inside at router 1. Now if this first ISP link gets down then it should be accessible by other ISP but I have done NAT with first router's IP which has been provided by first ISP so i m confused that what should I do now because I cant do NAT with other IP on other router within second ISP IP range.Means this global IP should be same, it doesnt matter which ISP I m using.

Thanx and Regards,

Taran

Hi Taran,

Genrally says it is not possible when you have natted with single ISP and if that ISP goes down then the associated natted ip will also goes down.Genrally in your type of scenarios peoples used to do nat with both available ISP to have high availabilty of the private ip most probaly web servers and float those to external authorative DNS so that both the ISP public ip will be used.

and you can also use Link load balancer to load balance the outgoing and incoming traffic on the basis of dns query from external world for incoming traffic and natting can be used in Link load balancers for both the ISP also.

Hope to help

Ganesh.H

tarnhundal Wed, 01/27/2010 - 01:25

Hi Ganesh,

                          Thanx for reply. I m not sure will this work in my scenario because I m using 2 routers connected with one switch and I think load-balancer will work only on one router and second thing is that i m using static nat for a application server , so i think it wll not be accessible by second router .what u say ?

thanx and regards,

Taran

Ganesh Hariharan Wed, 01/27/2010 - 01:34

Hi Ganesh,

                         Thanx for reply. I m not sure will this work in my scenario because I m using 2 routers connected with one switch and I think load-balancer will work only on one router and second thing is that i m using static nat for a application server , so i think it wll not be accessible by second router .what u say ?

thanx and regards,

Taran

Hi Taran,

No Genrally load balancer like Radware link load balancers can be used to load balance the outbound traffic as you have switch in which both the ISP are getting connected so LLB will be reachable with both the ISP via switch to load balance the out going traffic.

Yes as you have configured static nat with only one ISP it wont be accesible via second ISP in case if first ISP goes down just see the basic concept if the public ip which is natted in internet is not reaching or getting advertise to other isp due link failure then nobody can access that public ip from anywhere.

Hope that clear your query !!

If helpful do rate the valauble post

Ganesh.H

tarnhundal Wed, 01/27/2010 - 02:09

Hi Ganesh,

                             Thanx for reply . So I m thinking to NAT this LAN IP with other ISP's public IP. It means I have to use 2 IPs for this . Am I right ?

thanx and regards,

Taran

Correct Answer
Ganesh Hariharan Wed, 01/27/2010 - 02:14

Hi Ganesh,

                            Thanx for reply . So I m thinking to NAT this LAN IP with other ISP's public IP. It means I have to use 2 IPs for this . Am I right ?

thanx and regards,

Taran

Hi Taran,

Yes you need to nat with second ISP public pool ip in second isp router with the local lan private ip of the server.

Hope to help

Ganesh.H

tarnhundal Wed, 01/27/2010 - 02:45

Hi Ganesh,

               Thanx for update.

Thanx and regards,

Taran

Actions

This Discussion