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Acquiring multiple dynamic IPs from ISP?

Unanswered Question
Mar 7th, 2003
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Hi! I asked this before but no helpful advice came up.


I'm running C2600 with WIC-1ADSL module. It is connected to normal ISP providing end users (home users) five dynamic public IPs for five different hosts.


Inside network is running on private 192.168.x.x addresses and can reach the Internet via NAT. C2600 does NAT against one of the dynamic IPs that is currently in use of BVI1.


I'd like to have the rest four of them to be able to NAT different things via different IP and I also need to be able to run a VPN gateway behind NAT. As far as I know, this will work over NAT if that address is not used for other traffic.


How can I put the C2600 to get all the available IPs to virtual interfaces etc..?


I'm running 12.2.4T5 software with features of IP/FW/IDS PLUS IPSEC (that release is one of the few that supports WIC-1ADSL on C2600 platform).


Thanks!


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tepatel Fri, 03/07/2003 - 14:44
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  • Cisco Employee,

The dsl interface will get just one ip address assigned to it from isp. But since isp has allocated 5 ip address for that connection, you can use rest 4 public ip address for NAT pool and map those 4 ip address with the internal ip address like web server, email server, vpn server.


When isp gives more then one ip address (a subnet) for a connection, it will install a static route for the subnet allocated to that connection with a default gateway.


So lets say you will be given 1.1.1.1 to 1.1.1.6 with subnet mask /29 and if it allocates 1.1.1.1 to dsl interface. ISP will install a route like this

ip route 1.1.1.0 255.255.255.248 1.1.1.1

Where for rest 1.1.1.2 to .6 the default gateway is 1.1.1.1

So all the packets to .2 to .6 will be forwarded to 1.1.1.1.


So you can have rest .2 to .6 for global outside ip nat pool which you can statically map them to internal ip address for web,email,vpn server etc.

Hope this explains.

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