Cisco Systems IPSEC Multiple Modems on same Subnet

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Subject Author Date
IPSEC Multiple Modems on same Subnet derSchweiz 01-28-07
Posted by derSchweiz on January 28, 2007, 12:14 am
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Hi,

I want to setup multiple modems to aggregate bandwith between two sites
using Cisco CEF Per-Packet and IPSEC crypto maps. I have 5 cable modems,
which are connected to a switch, each of them on its own VLAN, and a 802.1q
trunk that runs from the switch to Cisco router, to get virtual interfaces
to access the modems. Same setup at both sites.

What could I do if the ISP assigns IP addresses that are on the same subnet
to each of these modems? i.e. 5 IP addresses are all in the 24.1.2.0/24
subnet? If I try to assign these addresses to the interfaces of the router,
it will show an error saying that addresses overlap. Is there a easy way
around this problem? Maybe some sort of NAT to hide the external addresses?


Any help appreciated.

Thanks in Advance!



Posted by derSchweiz on January 28, 2007, 5:10 pm
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In other words would this work? Will there be any complications when setting
up IPSEC tunnels using this configuration?

24.1.2.1----<NAT>---10.0.0.0/30---[RouterA-Virtual Interface fa0/0.1]
24.1.2.2----<NAT>---10.0.0.4/30---[RouterA-Virtual Interface fa0/0.2]
24.1.2.3----<NAT>---10.0.0.8/30---[RouterA-Virtual Interface fa0/0.3]
24.1.2.4----<NAT>---10.0.0.12/30---[RouterA-Virtual Interface fa0/0.4]
24.1.2.5----<NAT>---10.0.0.16/30---[RouterA-Virtual Interface fa0/0.5]



> Hi,
>
> I want to setup multiple modems to aggregate bandwith between two sites
> using Cisco CEF Per-Packet and IPSEC crypto maps. I have 5 cable modems,
> which are connected to a switch, each of them on its own VLAN, and a
> 802.1q trunk that runs from the switch to Cisco router, to get virtual
> interfaces to access the modems. Same setup at both sites.
>
> What could I do if the ISP assigns IP addresses that are on the same
> subnet to each of these modems? i.e. 5 IP addresses are all in the
> 24.1.2.0/24 subnet? If I try to assign these addresses to the interfaces
> of the router, it will show an error saying that addresses overlap. Is
> there a easy way around this problem? Maybe some sort of NAT to hide the
> external addresses?
>
>
> Any help appreciated.
>
> Thanks in Advance!
>



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