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Public IP Address Routing

fatalXerror
Level 5
Level 5

Hi Guys,

Good Day!

Just want to have confirmation regarding public IP routing over the internet.

I will be having 2 ISP (primary and backup) and I have servers behind my firewall which has static IP address using my PRI-ISP. My question is, once my PRI-ISP goes down, my servers should still be reachable right via the static NAT public IP address even if I use my STBY-ISP?

Please see diagram.

Thanks

7 Replies 7

Hello,

It is depending on many things. Do you have BGP between you and your ISPS?

How are your advertising your IP addresses?

What are those devices between ASAs and your service providers?

And still more...

Masoud

Hi Masoud,

Good Day!

Actually, we don't have BGP advertisement. We just use static routing in between my ASA and the ISP. Then we have servers in the DMZ with static NAT using my PRI-ISP public IP addresses.

Thanks.

How about your second ISP? You are probably getting different IP address from your second ISP.

Masoud

Hi Masoud,

Good Day!

Actually, both ISPs will be via static routing only and the 2 ISPs has different public IP subnets.

I just asked this because in my mind public IP address should be routable right? so if I use my 2nd ISP the public IP in my 1st ISP should be still reachable?

Thanks.

No, it is not. It is not reachable unless you advertise your IP addresses through BGP.

I hope it is clear.

Masoud

Hi

Unfortunately it is not possible as mentioned Masoud. If the Primary ISP is down, you must change the public IP of your static NAT by one IP associated to the backup provider. You could try to do it automatically using EEM script. 




>> Marcar como útil o contestado, si la respuesta resolvió la duda, esto ayuda a futuras consultas de otros miembros de la comunidad. <<

Hi Julio,

Good Day!

Thanks for the feedback.

What if, I also configure another static NAT for each of my server? Do you think it will work?

Do you have samples for the EEM for ASA?

Thanks

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