The most common transition method for IPv6 (that is: how to enable IPv6 on a network that does not have a native IPv6 connection to the Internet) is a “6in4” tunnel. Other tunneling methods such as Teredo or SixXS are found on different literatures as well. However, another method that is not often explained is to tunnel the IPv6 packets through a normal VPN connection. For example, if the main office has a native IPv6 connection to the Internet as well as VPN connections to its remote offices, it is easy to bring IPv6 subnets to these stations. Here comes an example with two Palo Alto firewalls.
How to route traffic inside an IPv6 site-to-site VPN tunnel if one side offers only dynamic IPv6 prefixes? With IPv4, the private network segments were statically routed through the tunnel. But with a dynamic prefix, a static route is not possible. That is, a dynamic routing protocol must be used. Here is an example of how I used OSPFv3 for IPv6 between my VPN endpoints.
In detail, I have a home office with a dual stack ISP connection. However, this connection has a dynamic IPv6 prefix: After every reboot or lost connection of the firewall, I get a new IPv6 prefix. This is really bad for building a site-to-site VPN to the headquarter. Since I don’t want to use any kind of NAT/NPTv6 with unique local addresses, I am talking OSPFv3 over the VPN tunnel in order to route the dynamic prefix range (global unicast) via the tunnel.
The Juniper ScreenOS firewall is one of the seldom firewalls that implements DHCPv6 Prefix Delegation (DHCPv6-PD). It therefore fits for testing my dual stack ISP connection from Deutsche Telekom, Germany. (Refer to this post for details about this dual stack procedure.)
It was *really* hard to get the correct configuration in place. I was not able to do this by myself at all. Also Google did not help that much. Finally, I opened a case by Juniper to help me finding the configuration error. After four weeks of the opened case, I was told which command was wrong. Now it’s working. ;) Here we go.
With global IPv6 routing, every single host has its own global unicast IPv6 address (GUA). No NAT anymore. No dirty tricks between hosts and routers. Great. Security is made merely by firewalls and policies. Site-to-site VPNs between partners can be build without address conflicts. Great again!
However, one problem to consider is the proper IPv6 routing via site-to-site VPNs since both sides now can reach each other even without a VPN. This was (mostly) not true with IPv4 in which both partners heavily relied on private RFC 1918 addresses that were not routable in the Internet. If specific IPv6 traffic should flow through a VPN but does actually traverse the Internet, it would be easy for a hacker to eavesdrop this traffic, leading to a security issue!
The following principles should be realized properly to assure that IPv6 traffic is never routed through the mere Internet when a site-to-site VPN tunnel is in place. Even in a failure of that tunnel. The principles can be applied to any IPv6 tunnels between partners, remote sites, home offices, etc., as long as the other site has its own global unicast IPv6 address space. (For VPNs in which a sub-prefix from the headquarters prefix is routed to a remote site, the situation behaves different. This article focuses on the routing between different IPv6 adress spaces.)
Similar to my test lab for OSPFv2, I am testing OSPFv3 for IPv6 with the following devices: Cisco ASA, Cisco Router, Fortinet FortiGate, Juniper SSG, Palo Alto, and Quagga Router. I am showing my lab network diagram and the configuration commands/screenshots for all devices. Furthermore, I am listing some basic troubleshooting commands. In the last section, I provide a Tcpdump/Wireshark capture of an initial OSPFv3 run.
I am not going into deep details of OSPFv3 at all. But this lab should give basic hints/examples for configuring OSPFv3 for all of the listed devices.
While reading the OSPF chapter in the Cisco CCNP ROUTE learning guide, I was interested in how to visualize an OSPF area. Since every router in the same area has a complete view of all routers and networks, it should be easy to draw a map. So, I searched through the web for this kind of OSPF plotter and found two different approaches. While none of them worked out of the box, I was able to run one of them with an additional software router (Quagga) inside my OSPF area which finally drew a map. Yeah. Here we go:
Cisco ASA 9.4 (and later) is now supporting Policy Based Routing. Yeah. Great news, since many customers are requesting something like “HTTP traffic to the left – VoIP traffic to the right”. Coming with a new Cisco ASA 5506-X I was happy to try the policy based routing feature.
The configuration steps through the ASDM GUI are not easy and full of errors, so I try to give some hints within this blog post.
This guide is a little bit different to my other Policy Based Forwarding blog post because it uses different virtual routers for both ISP connections. This is quite common to have a distinct default route for both providers. So, in order to route certain traffic, e.g., http/https, to another ISP connection, policy based forwarding is used.
I already puslished a blog post concerning policy-based routing on a Juniper firewall within the same virtual router (VR). For some reasons, I was not able to configure PBR correctly when using multiple VRs. Now it works. ;) So, here are the required steps:
This is a small example on how to configure policy routes (also known as policy-based forwarding or policy-based routing) on a Fortinet firewall, which is really simple at all. Only one single configuration page and you’re done. ;)
The most common transition method for IPv6 (that is: how to enable IPv6 on a network that does not have a native IPv6 connection to the Internet) is a “6in4” tunnel. Even other tunneling methods such as Teredo or SixXS are found on different literatures. However, another method that is not often explained is to tunnel the IPv6 packets through a VPN connection. For example, if the main office has a native IPv6 connection to the Internet, as well as VPN connections to its remote offices, it is easy to bring IPv6 subnets to these stations.
Here is how I did it with some Juniper SSG firewalls:
A commonly misunderstanding of traceroute is that it fully relies on ping. “If I block ping at my firewall, no one can use traceroute to reveal my internal routing path”. Unfortunately this is not true. If traceroute is used with TCP SYN packets on permitted TCP/UDP ports, all intermediary firewalls will handle the IP packets with TTL = 0 corresponding to the RFCs and will reply with an ICMP time exceeded packet to the source.
In this post I am listing an example that uses traceroute with TCP port 25 (SMTP) to traverse a firewall. A sample pcap file can be downloaded while some Wireshark screenshots show a few details.