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Best way to pass IPv4 and IPv6 traffic over a GRE Tunnel

Nikolaos Milas
Level 1
Level 1


We have two 3825 routers with Advanced Enterprise IOS 12.4.9(T). Each of them serves many IPv4 (private and public) and IPv6 networks on their respective site.

We have created a wireless link between the two, using 4 wireless devices, with IP Addresses, 3, 4, 5 respectively (1 and 6 are the two end Ethernet interfaces on the routers).

Then we created a GRE tunnel over this link using addresses and 2 (for the two ends) to route traffic over this link.

Now we want to route IPv6 traffic over the same link. However, we found that simply routing the IPv6 traffic over the above GRE / IP tunnel did not work.


  • Is there a way we can use the same (GRE / IP) tunnel to transport both IPv4 and IPv6 traffic?
  • If not, can we setup two GRE tunnels over the same wireless link, that is, one GRE / IP for IPv4 traffic and a second one GRE / IPv6 for IPv6 traffic?

In brief, what is the suggested way to transport IPv4 and IPv6 traffic over the aforementioned (wireless) link?

I have read and other Internet material, however I am still confused.

Please help.

Thanks in advance,


1 Reply 1

Nikolaos Milas
Level 1
Level 1

We have set up two tunnels over the same link, one GRE / IP for the IPv4 traffic and one IPv6 / IP ("manual") for the IPv6 traffic. This setup seems to be working OK.

If there are other suggestions, please advise.