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New Member

isp redundancy 24*7

we have 2 ISP and 2 public pool from different ISp if one goes down applications are not accesible from outside .i want total redundancy

can any body suggest solution for that


Re: isp redundancy 24*7


I don't think IP provided One ISP will be allowed by another ISP provider.

I suggest you to have some IP taken from internet registry and ask both provider to allow both the pool.

Then you will have flaexibility to move traffic as per your requirement



New Member

Re: isp redundancy 24*7

is ther need to go for bgp with AS

Re: isp redundancy 24*7


Public AS is required, b'se no all ISP will allow customer owned IP address to be advt. on internet with source as his own AS

to avoid blacklisting of AS.



Re: isp redundancy 24*7

Hello Kukreja,

As said, purchase a APNIC IP Pool and route as below. Assume you have a requirement of /23 IP Pool for your Network and purchase the same from APNIC or RIPE based on your region/location.

Divide the /23 IP Pool into 2" /24 IP networks:

Viz ISP-A route as,

1st /24 as Primary

/23 as Secondary

Viz ISP-B route as,

2nd /24 as Primary

/23 as Secondary

In this case, if your ISP-A fails the next longest match for your network will be available viz ISP-B and vice versa. You can apply the same for multiple IP Pools unless and until it is purchased from the APNIC or RIPE.

Please Rate if Helps !

Best Regards,

Guru Prasad R

Re: isp redundancy 24*7

An alternative is to check with the ISPs and see if you can have one of the IP blocks be portable, IE, advertised by the second provider into BGP as well.

Then your BGP session advertises one IP block, and both providers allow them into their BGP advertisements to the net. I know that several providers will allow this, like Internap and Qwest. It never hurts to ask. :)

The best option is always to get your own IP block from your local IP registry and use it in your BGP session.

New Member

Re: isp redundancy 24*7

Guru Prasad can u post configuration and live scenario to help in such a matter

We have two isp each have individual internet router and each have individual firewall each have individual public ip pool for dmz servers

i need configuration detail live scenario. can u tell me what is the cost of AS No. IP pool and other things as u suggest to discuss with ISP

New Member

Re: isp redundancy 24*7

can any body help in this matter ?

Re: isp redundancy 24*7

The cost for an AS Number is somewhere in the $500USD range from ARIN. You need to check your local regional registry for IP addresses and numbers for their fee schedu

le. Common ones are:

ARIN = Canada, many Caribbean and North Atlantic islands, and the United States;

RIPE = Europe, the Middle East and parts of Central Asia.

AfriNIC = Africa

APNIC = Asia Pacific

LACNIC = Latin America and the Caribbean

The cost for IP blocks depends on how many IP addresses you need, so you should check with the registrars.

Ideally, you will have two routers connected via iBGP, and each router has an eBGP session with their respective ISP. You then point your default gateway at the redundant address (via HSRP, GLBP, or VRRP) of your internet routers, and let the rest be handled by BGP.

The alternative to getting your own ASN and IP space is to do a private ASN arrangement with your ISP (think like private addressing) to advertise one of your two delegated IP blocks to both providers. For example:

RouterA connects to ISP-A, and has external IPs of

RouterB connects to ISP-B, and has external IPs of

You talk to both ISPs and they agree to let you advertise to both of them. Obviously, ISP-B has to allow the IP traffic for into their network now, which was normally only destined to ISP-A. This is why the ISPs must talk and agree to this.

From the internet, my computer sends traffic to my router, which has BGP tables showing the best route to If it happens to be through ISP-B, then the traffic comes in that path. This way, it assures that you maintain one IP space and have redundant ISP paths for your network. If ISP-A goes down, traffic can come through ISP-B. If ISP-B goes down, traffic can come through ISP-A. You don't need to change DNS or any of that other stuff because your IPs don't change.

Obviously, if you own the IP block, the ISPs will allow you to advertise it freely. The nice thing there is that if you decide to change from ISP-A to ISP-C, you don't have to go through this whole exercise again because ISP-A won't let you keep if you leave their service.

Hope that helps.