IPsec quick and dirty

Monday, August 15, 2011 at 1:57 a. The policy may dictate that only some or all of the traffic being evaluated is placed into the VPN. In contrast to a iPsec quick and dirty-based VPN, a route-based VPN employs routed tunnel interfaces as the endpoints of the virtual network. All traffic passing through a tunnel interface is placed into the VPN.

IP routes are formed to direct the desired traffic through the VPN tunnel interface. The lab topology employed in this article is easily replicated using Dynamips or the community lab, and I encourage readers to play along in a lab of their own while reading. If you do, be sure to bookmark this VPN troubleshooting guide from Cisco before you begin. It can be a real time-saver should you run into a wall.

Our goal is to form two VPNs across the “public” network represented by the 172. And before anyone brings up my New Year’s pledge, I am planning to replicate both VPNs configurations using IPv6 in the future. I just wanted to keep the IP architecture as simple as possible for now since we’re already dealing with two fairly complex topics. The first part of this article covers setting up a policy-based VPN between R1 and R3.

The second part will cover the configuration of a route-based VPN tunnel between R1 and R5, and discuss some pros and cons to both approaches. Step 1: Define an access list to match interesting traffic This is the policy part of policy-based VPNs. We need to define an access list to match all the traffic we want to send through the VPN between the two routers. For our purposes, we only need to match traffic between the two LANs attached to R1 and R3.

Specifically, we need to match traffic from 10. 24 on R1, and from 10. This results in two ACLs which mirror each other, one on either router. This is easy when we only have one permit statement, but can become burdensome when dealing with numerous policy entries. In the real world, public key authentication provides much better security. This sets the parameters which will be used by the routers during IKE phase one, when the initial asymmetrically-encrypted ISAKMP SA is negotiated. This policy is applied identically to both routers.

We specify the keyring to be used for this peer so that the router knows how to locate the correct pre-shared key. After creating the crypto map, apply it to the appropriate interface on each router. 3 set transform-set ESP-AES256-SHA1 set isakmp-profile R1_to_R3 reverse-route static set reverse-route distance 10 ! 1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 10. 1, timeout is 2 seconds: Packet sent with a source address of 10. The next four pings succeeded, and we can verify that an ISAKMP SA was established.

IPv4 Crypto ISAKMP SA dst src state conn-id status 172. About the Author Jeremy Stretch is a network engineer living in the Raleigh-Durham, North Carolina area. He is known for his blog and cheat sheets here at Packet Life. You can reach him by email or follow him on Twitter. August 15, 2011 at 4:45 a. Why did you consider to use keyrings and Isakmp profiles instead of applying the config global?

August 15, 2011 at 7:16 p. Very well explained, keep up the good work! August 16, 2011 at 11:03 a. I have never known about reverse-route static directive. August 16, 2011 at 9:36 p. I don’t understand how you can ping the 10. Did you create a subinterface for this network?

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By the way, congratulations for the post! August 17, 2011 at 1:23 a. 24 was assigned to a loopback interface on R3 to emulate an internal network. This is common practice when dealing with lab topologies which aren’t quite as big as a real network. I’ve posted the finished configs from all three routers at the end of part two, which might help. August 17, 2011 at 2:12 p.

August 21, 2011 at 5:04 p. August 22, 2011 at 2:56 a. August 22, 2011 at 3:22 p. Just wanted to say i’ve read many of your new posts as well as the old ones. They are all really well written, straight to the point, perfectly formatted and diagrams top notch. I really like the way you represent code examples.

Makes your posts so easy to read. Thank you for all the time and effort you put into these. August 22, 2011 at 3:45 p. August 25, 2011 at 8:27 a. November 15, 2011 at 6:37 a. November 30, 2011 at 12:38 p.

April 2, 2013 at 4:58 a. In the last part of this guide, you state “We can generate some traffic to trigger the creation of the VPN by performing a simple ping whose source and destination addresses are matched by the VPN policy” and “Successive pings will all succeed so long as the VPN tunnel doesn’t time-out”. How can you open a tunnel and keep it open? May 6, 2013 at 12:12 p. Nice post, a quick question will ASA support both policy and route based vpn?

June 18, 2013 at 12:09 p. May 13, 2014 at 11:48 p. January 25, 2016 at 6:58 a. March 15, 2016 at 8:50 p.

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Your post is remarkable helpful everyone like me. If you have any example please let me know. That would be a great help for me. July 21, 2016 at 1:14 p. Comments have closed for this article due to its age.

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Monday, July 11, 2011 at 1:37 a. Vlan1 nameif outside security-level 0 ip address 172. Vlan2 nameif inside security-level 100 ip address 10. While it is possible to enable several options, both sides of our VPN will be configured to support only 256-bit AES and SHA-1. IPsec tunnel between the two LANs. Since we’re using pre-shred key authentication, we need to name our tunnel group as the IP address of the remote peer. IPsec transform set, access list, and tunnel group configured in the previous steps.

L2L 1 match address LAN_Traffic crypto map L2L 1 set peer 172. 9 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 10. 9, timeout is 2 seconds: . Total IKE SA: 1 1 IKE Peer: 172. Crypto map tag: L2L, seq num: 1, local addr: 172. 2       access-list LAN_Traffic permit ip 10.

The VPN traffic generated by the ping above looks like this. The first ICMP request across the VPN triggers the building of the VPN and is discarded. The remaining four ICMP requests and responses are encrypted in the eight ESP packets at the end of the capture. About the Author Jeremy Stretch is a network engineer living in the Raleigh-Durham, North Carolina area.

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He is known for his blog and cheat sheets here at Packet Life. You can reach him by email or follow him on Twitter. July 11, 2011 at 4:05 a. Is there any special considerations for doing this with IPv6?

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July 11, 2011 at 6:53 a. Do you know any possibility to monitor your VPN ? Like SNMP trapping or anything else to check remotly if it’s alive ? Do you know a way to check since when the VPN goes on ? July 11, 2011 at 8:28 a. July 11, 2011 at 10:10 a.

It’s probably worth mentioning that these type of connections are typically done through the ASDM as it reduces the risk of entering a typo. Also, anyone who attempts this in a live environment should check that traffic directed at the peer isn’t caught by a route that points the traffic at the internal interface of the ASA. I’ve seen this a few times and its easily missed. Nice article, an example with NAT would be interesting as well. July 11, 2011 at 1:10 p.

July 11, 2011 at 2:56 p. I hate the way the ASDM creates site-to-site VPNs. I think its messy and confusing and much prefer to create them via a template in notepad or similar and use the cli. Another thing to consider which also catches some people out is to make sure that if there are global NAT rules in place for certain ranges that need access to the internet, make sure you create a NAT exempt rule for the interesting traffic. July 11, 2011 at 7:52 p. July 11, 2011 at 8:39 p. Just a few days ago I posted a video tutorial on how do do this using a GRE tunnel between two routers connected to the internet.

Glad to see that the basic steps are the same using ASA or a router. July 11, 2011 at 10:02 p. Also note that the ASA’s may be performing NAT between inside and outside. Because NAT will be performed before checking the crypto ACL, the traffic won’t actually match the crypto ACL and won’t be sent across the VPN.

July 12, 2011 at 7:00 a. The command “packet-tracer” is good for testing, too. July 12, 2011 at 11:34 a. July 12, 2011 at 6:43 p.

I had read as well alright. A quick google search hasn’t returned any recommendations though and I’m too lazy right now to check my books. July 12, 2011 at 7:34 p. Additionally, running debug, it would be very helpful to point out that Phase 1 of the tunnel refers to ISAKMP policy, while Phase 1. 5 is the preshared key, and Phase 2 is IPSec configuration which is managed by the crypto map statement.

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July 12, 2011 at 9:07 p. July 13, 2011 at 5:24 p. July 14, 2011 at 2:35 p. Kris it is probably better to take l2tpv3 out of the comparison as it is a different service all together – layer 2 delivery over a l3 cloud.

The vlan should be well protected with access-lists for permissions. July 19, 2011 at 6:18 a. That configuration is the same as for the 1841 and 2800? July 31, 2011 at 1:17 a. 21 vlan1 on access ports is only a bad idea if vlan1 is the native vlan on your trunks. October 6, 2011 at 8:59 a.

If there is LAN-to-LAN VPN using the pair of ASA 5505s between 2 sites. Can you have a subnetwork within one of the sites and connect to the subnetwork from a client? I am typacillty thinking, Headoffice to branch VPN as described in the article. So, in the Headoffice you have to VPN from a client PC to the project network and at the branch you do the same, provided that the branch is connected via it’s VPN to the head office. October 6, 2011 at 1:42 p. I have one site with multi site connections through WAN.

I have done similar configurations, but got two problem. From one of the branches I can initiate, but from the main site I cann’t. The same configuration done on the 2nd site but I cann’t initiate from that site. October 6, 2011 at 2:11 p.

I connect LAN-to-LAN VPN using the ASA 5510 at the main site ASA5505 at the other sites through WAN. I have done similar configuration on the main site and two other sites. Ican ping and intiate from the inside of one of the sites, but I canon’t ping and intiate from the main site. I can ping the outside network of the main site, but I cann’t ping and initiate the inside network of the main site. October 27, 2011 at 10:18 a. I’m running into some trouble with the ASA 5520.

I have two identical units for the purpose of failover, the problem is that if I were to displace the cable for an uplink to the switch, it will not failover to the second ASA. However, if I were to power down the ASA completely it will switchover to the secondary ASA. Any help on this would greatly appreciated. January 20, 2012 at 2:30 p.