2 ISP 1 Router,2 static NAT entries will be pointing to 1 private address

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Apr 19th, 2007
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Hi,

i have 2 ISP & it is connected to 1 Router, now my requirement is like this, i have 1 Private IP which will hav a 2 Static NAT(1 with ISP-1 & the other with ISP-2) my idea is.... even if 1 ISP fails the host name should get resolved with the other IP so that my server which is residing inside my office(private) will be reachable from the internet. so i was assuming with the DNS it is possible by setting up the priority for 1st IP & if that failz the DNS will look for the 2nd IP, is that correct what i am said?


eg.

if someone tries abc.co.in 1st it will lookin for 1.1.1.1(public IP)------>192.168.1.1(private) & if 1.1.1.1 ISP is down, with the DNS config. it should lookin for the 2nd ISP based on the priority like

2.2.2.2(public IP)------>192.168.1.1.


i think static NAT can also be configured with the priority kind of thing, i belive. am i right?


Static NAT entry on my router would be like this...


1.1.1.1------>192.168.1.1 high priority

2.2.2.2------>192.168.1.1 low priority


is that possible in the router for NAT priority?


or else suggest me where i should still able to reach my webserver or FTP server which is residing in my LAN private IP(residing behind firewall)

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Anand Narayana Thu, 04/19/2007 - 04:37
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thankz amit,

but for my requirement should i use "Equal Access" or "Differing Next Hops", i am not clear with the exact meaning. can u explain for these two? & also in that example. which is the public & private IP address.

Amit Singh Thu, 04/19/2007 - 04:43
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You should typically use Differeing next hops but in your scenario the config will be slightly different. You have to use only one route map statement with 2 next hop IP's. For example


access-list 1 permit ip 1.1.1.1


route-map ABC permit 10

match ip address 1

set ip next-hop 2.2.2.2 3.3.3.3


In this case when the prefeered ISP is down, the traffic from the host will be sent using the another ISP address.


HTH,

-amit singh

Anand Narayana Thu, 04/19/2007 - 04:55
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thankz amith,

but what is 1.1.1.1 ip address, is that much webserver or ftp server private ip address? is 2.2.2.2 is ISP-1's public IP & 3.3.3.3 is ISP-2's IP am i right?


also one more thing,

i should do a static NAT & then the above config. i should enter? or else the above entry alone will be sufficient?

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