L2TPv3 tunnel behind NAT

[Disco_20]

Hi CsicoCommunity 

I’ve been tasked to provide Laptop with internet connectivity via x4 cascaded routers.
I can use only static IP address and Static IP routes. For simulation I will use Cisco IOSv routers in GNS3

Graphical picture is added:

ISP Modem
|
R1
|
R2
|
R3
|
R4
|
Connected Laptop 

Broadband modem with
IP: 87.110.156.22 MASK 255.255.252.0
Default GATEWAY: 87.110.156.1
DNS: 8.8.8.8
NAT: Masquerade

Local IP: 192.168.100.1 MASK 255.255.255.0
route add 192.168.100.0 MASK 255.255.252.0 192.168.100.254

I guess I am asking community advice on which routing technology should I use to solve this.

Should I use L2TPv3 tunnel between inside routers and NAT translation?. I will appreciate any comments.

[Georg Pauwen · Accepted solution]

Hello,

if what you want to accomplish is provide Internet connectivity for your laptop, all you need to do is add the network of the laptop to the access list used for NAT, on the top router (the one directly connected to the ISP modem...

[paul driver · Accepted solution]

Hello
You could just use a simple dynamic routing protocol such as  RIPv2 to connect the 4 routers and append a simple Dynamic PAT on router 1

Example:

Rtr1

int gig0/1
description Modem
ip address 87.110.156.22 255.255.252.0
ip nat outside

int gig0/0
description rtr2
ip address 10.1.12.1 255.255.255.252
ip nat inside

router rip
ver2
no auto
network 10.0.0.0
default-information originate

access-list 1 permit 192.168.1.0 0.0.0.255
ip nat inside source list 1 interface gig0/1

ip route 0.0.0.0 0.0.0.0 gig0/1 87.110.156.1

rtr2
int gig0/0
description rtr1
ip address 10.1.12.2 255.255.255.252

int gig0/1
description rtr3
ip address 10.1.23.1 255.255.255.252

router rip
ver2
no auto
network 10.0.0.0

rtr3
int gig0/0
description rtr2
ip address 10.1.23.2 255.255.255.252

int gig0/1
description rtr4
ip address 10.1.34.1 255.255.255.252

router rip
ver2
no auto
network 10.0.0.0

rtr4
int gig0/0
description rtr3
ip address 10.1.34.2 255.255.255.252

int gig0/1
description LAN
ip address 192.168.1.254 255.255.255.0

router rip
ver2
no auto
network 10.0.0.0
network 192.168.1.0

ip dhcp pool LAN
network 192.168.1.0 255.255.255.0
default-router 192.168.1.254
dns-server 8.8.8.8 8.8.8.4
lease 0 8