2 IPs over single FQDN

[Jonn cos]

Hi all,

This question may be bit OT to this forum but i need some suggestions on it. We are planning to deploy SSL based solution that will provide customers access to our portal. We are planning to use 2 different ISPs for redundancy purpose, so i am confused with the following

1) If i give IP to customers, then it wont be favourable to them since they manually need to change the IP if our primary ISP is down

2) If i use FQDN, then how will it change to other IP of a different ISP ?

I am new to this stuff, how this requirement is met in real life ? any suggestions pls ?

[Karsten Iwen]

2) If i use FQDN, then how will it change to other IP of a different ISP ?

in DNS you assign two IP-addresses to your FQDN which are delivered to the client. With that it's up to the client to try the second IP if the first is not reachable.

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[Jonn cos]

Sorry i didnt get it, i thought in DNS we can assign only one IP address at any given time ?

[Karsten Iwen]

no, you can assign multiple IPs. That is commonly used to achieve load-sharing among multiple servers without the need to buy an expensive load-balancer. Here is some additional info:

http://docstore.mik.ua/orelly/networking_2ndEd/dns/ch10_07.htm

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[Jonn cos]

Sir, thanks for the suggestion. it definetly is useful, but in my case we have 2 IPs that will be treated as primary and backup (if primary fails). What shall be feasible in this case

[Karsten Iwen]

A primary/backup scenario won't be so easy to achieve without bothering your users. One way to achieve that is that from the DNS you probe the availability of your primary connection. If the connection fails the DNS-records are rewritten to the second IP. Together with very short TTLs that could work. But it will be much easier to use both providers at the same time with the DNS load-sharing.

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[singhaam007]

Hi John,

Use ip sla configuration for redundancy or backup purposes . Outgoing traffic uses the primary ISP and then the secondary ISP, if the primary fails. Failure of the primary ISP causes a temporary disruption of traffic.

You can use portal Ip and tie it up with sla and crate backup link with second ISP.

Here is detail information.

http://www.cisco.com/en/US/products/hw/vpndevc/ps2030/products_configuration_example09186a00806e880b.shtml

please rate if this helps.

thanks