IPv6 loopbacks

Unanswered Question
May 11th, 2009


How can you create a loopback interface in IPv6 on a router that would allow you to simulate other networks?

I tried to run autoconfig on the loopback interface, but they get all of the same addressing. The address of ::1/128 is the loopback address, but to create multiple loopbacks, would ::2/128, ::3/128, etc. work?



I have this problem too.
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Harold Ritter Mon, 05/11/2009 - 18:07


When you say that they all get the same address, you probably mean that the loopback interfaces have IPv6 addresses part of the FE80::/10. These are link local addresses as shown in the following document:


These addresses are assigned automatically to each interface and serve for communication between IPv6 devices on a local link.

As for ::1/128, you can't configure it on any interface and you should get the following message if you try:

Router(config-if)#ipv6 address ::1/128

%Loopback0: Error: ::1/128 is invalid

One more thing, you can't configure autoconfig on the loopback as this command assumes that there is another device on the subnet from which you can get autoconfiguration information.

Your best option would be to configure valid ipv6 addresses statically on the loopback interface(s) as follow:

for instance

int lo0

ipv6 address 2001:db8;12ff::1/128


ipv6 address 2001:db8;12ff::/64 eui-64



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