We help IT Professionals succeed at work.

Cisco LAN-to-LAN IPsec Tunnel Between Two Routers with a NAT device in the middle

Last Modified: 2014-11-22

Topology is

Cisco 881 (Outside on the Internet) wanting to create a number of tunnels to Cisco 881's inside a MPLS network. The MPLS provider has provided a Gateway with a Public IP address and they  have created a different IKE and IPSEC port for each inside host that we want to create a tunnel too.

I.e IKE 4510 / IPSEC 45010 redirect inside to inside Host IKE 500 / IPSEC 4500

Can I on my Cisco 881 on the Internet specify the destination ports that happen in Phase 1 and Phase 2?

Running a very basic L2L Config atm between hosts within the MPLS as per Cisco - http://www.cisco.com/c/en/us/support/docs/routers/1700-series-modular-access-routers/71462-rtr-l2l-ipsec-split.html

 Kind Regards

Watch Question

I'm not sure why you want to use different ports for the tunnels.  You can have multiple tunnels connected over the same ports.


Different EP's behind the traversal device in the middle


Traversal device isn't terminating the tunnels
This one is on us!
(Get your first solution completely free - no credit card required)


I thought as much, the tunnels are created from the public internet through to the internal EP so they will need a dedicated public IP per private EP. One would assume.

That would be my understanding as well.  No way you could combine those end points into one larger one and route the tunnels out from there?


I am afraid not, I wish. I pushed to have a connection into the site that was on the MPLS but some bright spark thought it best to put it behind a NAT traversal box.

I didn't think there was an option to specify the ports on a Cisco config but they insisted you can.

Looks like you can use encapsulation on an ASA, but if you are using IOS devices you are out of luck.


Gain unlimited access to on-demand training courses with an Experts Exchange subscription.

Get Access
Why Experts Exchange?

Experts Exchange always has the answer, or at the least points me in the correct direction! It is like having another employee that is extremely experienced.

Jim Murphy
Programmer at Smart IT Solutions

When asked, what has been your best career decision?

Deciding to stick with EE.

Mohamed Asif
Technical Department Head

Being involved with EE helped me to grow personally and professionally.

Carl Webster
CTP, Sr Infrastructure Consultant
Empower Your Career
Did You Know?

We've partnered with two important charities to provide clean water and computer science education to those who need it most. READ MORE

Ask ANY Question

Connect with Certified Experts to gain insight and support on specific technology challenges including:

  • Troubleshooting
  • Research
  • Professional Opinions
Unlock the solution to this question.
Join our community and discover your potential

Experts Exchange is the only place where you can interact directly with leading experts in the technology field. Become a member today and access the collective knowledge of thousands of technology experts.

*This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.


Please enter a first name

Please enter a last name

8+ characters (letters, numbers, and a symbol)

By clicking, you agree to the Terms of Use and Privacy Policy.