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New Member

2 isp plan


- planning to have two (isp) for internet connectivity high availability.

- host our own website

- host our own mail server

- all will be located on a DMZ and will be natted to an external public IP


- 2 diff isp will provide diff block of ip address.

I thought of registering 2 public IP for the webserver but when one isp link is down, then there will be 50 percent miss as well as 50 percent hit.



Re: 2 isp plan


If possible you can place the webserver in one of the SP DC so that it will be available all the times.


New Member

Re: 2 isp plan

Option 1:- get your own IP Space and configure BGP in a multi-homed environment, this will give you 100% redundancy.

Option 2:- Use a device like RADWARE Linkproof which can provide you ISP redundancy. This can give you 100% redundancy as well.

Option 3:- Some ISP's advertise the networks of other ISPs as well. This can be tried as well.

New Member

Re: 2 isp plan

just got the below explanation regarding radwares from the below link

"There are products, such as ones from Radware ( and StoneSoft ( that claim to handle this addressing problem for you. What these products do is work with DNS or DDNS (Dynamic DNS) so that only the currently working IP address will appear in public DNS records. This technique only works when caching of DNS records is either totally disabled, or the cache timeout (time to live) value is set to a very short interval. Disabling DNS caching is considered an abuse of the DNS system. Instead of a browser resolving your HTTP server's domain name once, it must do so for every connection it makes, placing additional loads on your network and DNS server, as well as the rest of the Internet"

New Member

Re: 2 isp plan

I have used RADWARE a lot and each time i used to log into the system for some configuration, i used to pray 10000 times... personally i have never liked that box... the best option is to have your own IP space and do BGP multi homing.

New Member

Re: 2 isp plan

ok. not an option then for radware..lets do bgp then..

any other suggestions from this forum?


New Member

Re: 2 isp plan

If you want tb be redundant across two ISPs the only workable option is to get your own IP addresses and ASnr, set up BGP with both ISPs and announce your network to both of them. In that case, when one link fails, the BGP route through that ISP will be withdrawn.

Using a DNS solution won't give you redundancy cause you cannot control which IP address the client chooses...

Of course you can also increase availability by hosting your servers with some reliable Cybercenter or so, enjoying their redundant setup, but I suppose that was not the solution you are looking for (it is less fun for the network engineer but often better availability for your money).....