can ISATAP tunnel use 2002::/16?

[sarahr202]

Hi everybody

My book says ISTAP tunnels do not use special reserved range of ipv6 (2002::/16).

But when i configure istap tunnel using 2002::/16;  I did not get any error message.

Below is the config;

R1

interface Tunnel1

no ip address

no ip redirects

ipv6 address 2002::/64 eui-64

tunnel source Loopback1

tunnel mode ipv6ip isatap

R1# show ipv6 int tunnel 1

Tunnel1 is up, line protocol is up

  IPv6 is enabled, link-local address is FE80::5EFE:101:101

  No Virtual link-local address(es):

  Global unicast address(es):

    2002::5EFE:101:101, subnet is 2002::/64 [EUI]

thanks and have a great day.

[Peter Paluch · Accepted solution]

Hi Sarah,

ISATAP tunnels use addressing of this format:

:0000:5EFE:

Indeed, ISATAP tunnels do not use a special prefix but rather a specific format of the IPv6 addressing. Therefore, the router won't complain when using 2002::/16 prefixes, as they nicely fit into the 64-bit prefix. However, semantically, you are doing an incorrect thing if you are addressing ISATAP tunnels using 6to4 addressing because you are making the ISATAP tunnel appear as 6to4 tunnel to nodes using 6to4 tunneling.

Best regards,

Peter

[sarahr202]

Hi Peter.

I hope you had a good weekend.

One more question occured to me while sleeping.

My book says the address on isatap tunnel can be configured by using eui-64 format and manually.

If we want to configure the address manuall, should this address contain 5efe as well?

Can i configure like this:

2000:0:1:1:0:1:0202:0202/64 ( where 2.2.2.2 is tunnel source address)?

or  we must use 5efe?

thanks .