IPV6 ISATAP Router as Client

Answered Question
May 7th, 2009
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Hi Everybody,

Is there any way i can configure Cisco Router as ISATAP client. Another Cisco Router is configured as ISATAP sever.

I donot have Windows XP. So I want to test ISATAP server.

Is there anyway i can test ISATAP server with Cisco Router as ISATAP Client


Correct Answer by Harold Ritter about 8 years 2 weeks ago


I see you are using 12.4(25) on the server. Try using 12.4T on both the client and server.


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Overall Rating: 5 (2 ratings)
Harold Ritter Fri, 05/08/2009 - 09:56
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Try the following configuration on the router you want to use as a ISATAP client.


no ipv6 unicast-routing


interface Tunnel0

no ip address

no ip route-cache

ipv6 address autoconfig

ipv6 enable

tunnel source

tunnel destination

tunnel mode ipv6ip



hclisschennai Sat, 05/09/2009 - 06:29
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Hi Hritter,

At the outset i thank you very much for your post. It helped me a lot. I tried your configuration & it is working perfectly.

From IPV4 (ISATAP Client)with IP address iam able to ping remote IPV6 machine with ip address 2001:a:b:c::2.

But i am not able to telnet the IPV6 Machine from IPV4 (ISATAP Client). After adding the default route ::/0 200:3def:5efe:c0a8:0102 (ISATAP server Tunnel interface IP), i am able to telnet to the remote IPV6 machine.

I am surprised why is this behaviour of able ping and not telnet the remote IPV6 machine. But why i am able to telnet the same IPV6 Machine from IPV4 (ISATAP Client) after adding the ipv6 default route with gateway as tunnel ISATAP ipv6 address.

Can you please help me in clarifying this?


Harold Ritter Sat, 05/09/2009 - 12:03
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What level of code are you using on the ISATAP client? I just tried with 12.4(24)T and I can ping and telnet to the rest of the network. You shouldn't need to configure a default route on the router used as a client just as you do not need to configured a default route on a regular client as in IPv6 the default router is discovered dynamically via the RA messages.

You should see the following information on the ISATAP client:

ISATAP-client#sh ipv6 router

Router FE80::5EFE:C0A8:C02 on Tunnel0, last update 8 min

Hops 64, Lifetime 1800 sec, AddrFlag=0, OtherFlag=0, MTU=1480

HomeAgentFlag=0, Preference=Medium

Reachable time 0 (unspecified), Retransmit time 0 (unspecified)

Prefix 2001:DB8:12FF:1::/64 onlink autoconfig

Valid lifetime 2592000, preferred lifetime 604800


Harold Ritter Sat, 05/09/2009 - 12:16
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I just checked and in 12.4(24)T, the static default route is added automatically as shown below:

ISATAP-client#sh runn | incl ipv6 route

ISATAP-client#sh ipv6 route ::/0

Routing entry for ::/0

Known via "static", distance 2, metric 0

Route count is 1/1, share count 0

Routing paths:

FE80::5EFE:C0A8:C02, Tunnel0

Last updated 00:21:48 ago



hclisschennai Sun, 05/10/2009 - 02:03
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As you adviced i tried the same. I attached configuration of ISATAP server and Client configuration for your reference.

But the result is same. Until i configure the default route with gateway as ISATAP server Tunnel IP Address in the client, I am able to ping the remote IPV6 Machine and not TELNET the same machine. I am using IOS Version 12.4(25).

Can you please look into the configuration and help me


Correct Answer
Harold Ritter Sun, 05/10/2009 - 14:38
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I see you are using 12.4(25) on the server. Try using 12.4T on both the client and server.



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