IPv6 ISATAP configuration example with a Cisco router as a client

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This example demonstrates ISATAP configuration on the head-end router and a simulated ISATAP client using a Cisco router. Usually the client is a Windows PC with IPv6 enabled, initiating the tunnel. For testing and verification purposes, a Cisco router closest to the clients can act as a client. Check feature navigator to verify head-end router image supports ISATAP tunnels. Check feature navigator to verify simulated client router supports manually configured IPv6 over IPv4 tunnels.


ISATAP client.jpg


Head-end router configuration

ipv6 unicast-routing
interface Loopback0
 ip address
interface Tunnel1
 no ip address
 no ip redirects
 ipv6 address 2001:DB8:CAFE:65::/64 eui-64 <<<Any /64 IPv6 address will work
 no ipv6 nd ra suppress       <<< IPv6 ra is suppressed by default on tunnel. Need to re-enable for client auto-configuration.
 tunnel source Loopback0
 tunnel mode ipv6ip isatap

Simulated ISATAP client on Cisco router

interface ethernet0
 ip address
interface Tunnel1
 no ip address
 ipv6 address autoconfig
 ipv6 enable
 tunnel mode ipv6ip
 tunnel source ethernet0
 tunnel destination

Related show Commands

This section provides information you can use to confirm your configuration is working properly.

Certain show commands are supported by the Output Interpreter Tool (registered customers only), which allows you to view an analysis of show command output.

Show running-config

Client Tunnel1 should acquire IPv6 address prefix from head-end. Then it appends client source IPv4 address to then end. In this exampls, => 0F00:0001

 show ipv6 interface tunnel1 
 Tunnel1 is up, line protocol is up
 IPv6 is enabled, link-local address is FE80::F02:880 
 No Virtual link-local address(es):
 Stateless address autoconfig enabled
 Global unicast address(es):
   2001:DB8:CAFE:65::F00:0001, subnet is 2001:DB8:CAFE:65::/64 [EUI/CAL/PRE]
     valid lifetime 2591979 preferred lifetime 604779
 Joined group address(es):
 MTU is 1480 bytes
 ICMP error messages limited to one every 100 milliseconds
 ICMP redirects are enabled
 ICMP unreachables are sent
 ND DAD is enabled, number of DAD attempts: 1
 ND reachable time is 30000 milliseconds (using 30000)
 Default router is FE80::5EFE:F64:801 on Tunnel1

IPv6 Router advertisement information can be seen from,

 show ipv6 router
 Router FE80::5EFE:F64:801 on Tunnel1, last update 21 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:CAFE:65::/64 onlink autoconfig
   Valid lifetime 2592000, preferred lifetime 604800

If IPv6 unicast-routing is disabled on the client router, it will also install a default static route pointing towards the ISATAP head-end router.

show ipv6 route

IPv6 Routing Table - default - 4 entries
Codes: C - Connected, L - Local, S - Static, U - Per-user Static route
      B - BGP, R - RIP, I1 - ISIS L1, I2 - ISIS L2
      IA - ISIS interarea, IS - ISIS summary, D - EIGRP, EX - EIGRP external
      ND - Neighbor Discovery, l - LISP
      O - OSPF Intra, OI - OSPF Inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
      ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
S   ::/0 [2/0]
     via FE80::5EFE:F64:801, Tunnel1
C   2001:DB8:CAFE:65::/64 [0/0]
      via Tunnel1, directly connected
L   2001:DB8:CAFE:65::F02:880/128 [0/0]
     via Tunnel1, receive
L   FF00::/8 [0/0]
     via Null0, receive

Related Information

Technical Support & Documentation - Cisco Systems

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