Stateless Autoconfiguration IPv6 Cisco IOS

Nodes autokonfigurerer egen IPv6 adresse

• Stateless autoconfiguration består af
  • Prefix Advertisment
    • Routere annoncerer prefixer på link
    • RA – Router Advertisment ICMPv6 type 134
  • Duplicate Address Detection
    • Sikrer unikke IPv6 adresser på Link
    • NS – Neighbor Solicitation ICMPv6 type 135
  • Prefix Renumbering
    • Ændrede eller nye Prefixer annonceres af Routere
    • RA – Router Advertisment ICMPv6 type 134

K06_HOT_3030FW#<input>show ipv6 interface fastEthernet 0/1 prefix</input>
IPv6 Prefix Advertisements FastEthernet0/1
Codes: A - Address, P - Prefix-Advertisement, O - Pool
       U - Per-user prefix, D - Default
       N - Not advertised, C - Calendar

PD default [LA] Valid lifetime 2592000, preferred lifetime 604800
AD 2001:16D8:DD85:4::/64 [LA] Valid lifetime 2592000, preferred lifetime 604800

Router Advertisment Interval

Default interval

Router Advertisements are default sent every 200 seconds.

R1(config-if)#<input>do show ipv6 int fa0/0</input>
FastEthernet0/0 is up, line protocol is up
  IPv6 is enabled, link-local address is FE80::F225:72FF:FE3B:D6D2
  No Virtual link-local address(es):
  Description: Inside: Internal LAN
  Global unicast address(es):
    21:26::1, subnet is 21:26::/64
  Joined group address(es):
    FF02::1
    FF02::2
    FF02::1:FF00:1
    FF02::1:FF3B:D6D2
  MTU is 1500 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)
  ND advertised reachable time is 0 (unspecified)
  ND advertised retransmit interval is 1000 milliseconds
  <notice>ND router advertisements are sent every 200 seconds</notice>
  ND router advertisements live for 1800 seconds
  ND advertised default router preference is Medium
  Hosts use stateless autoconfig for addresses.

Changing Router Advertisement interval

Changing to sending 10 packets pr. second. (Not advisable though - too much traffic generated)

R1(config)#<input>interface fastEthernet 0/0</input>
R1(config-if)#<input>ipv6 nd ra interval msec 100</input>

Turning off Periodically send Router Advertisement

Notice

The Router will still respond to "Router Solicitation" packets and inform the Node of it's prefix on that link.

R1(config)#<input>int fa0/1</input>
R1(config-if)#<input>ipv6 nd ra suppress</input>

Turning off Router Advertisement

To turn of Periodically and answers to "Router Solicitation" packets. As seen in the picture below, RA is turned off on three of the interfaces.

R1(config)#<input>int fa0/1</input>
R1(config-if)#<input>ipv6 nd ra suppress all</input>

Showing Connected Routers Advertising

Heimdal#<input>show ipv6 routers</input>
Router FE80::128C:CFFF:FE96:F76F on Vlan1, last update 0 min
  Hops 64, Lifetime 1800 sec, AddrFlag=0, OtherFlag=0, MTU=1500
  HomeAgentFlag=0, Preference=Medium
  Reachable time 0 (unspecified), Retransmit time 0 (unspecified)
  Prefix <notice>2001:16D8:DD85:4::/64</notice> onlink autoconfig
    Valid lifetime 2592000, preferred lifetime 604800
Router FE80::218:18FF:FE7C:B440 on Vlan1, last update 0 min
  Hops 64, Lifetime 1800 sec, AddrFlag=0, OtherFlag=0, MTU=1500
  HomeAgentFlag=0, Preference=Medium
  Reachable time 0 (unspecified), Retransmit time 0 (unspecified)
  Prefix <notice>2001:16D8:DD85:4::/64</notice> onlink autoconfig
    Valid lifetime 2592000, preferred lifetime 604800

Prefix renumbering

With Autoconfiguration, it's quite easy to change to a new prefix in-flight.

Example

Changing to a new ISP will give you a new prefix

• Existing network: 2001:1::/64
  • Last Router Advertising is December 12. 2011 at 02:59.
• New subnet 21:26::1/64 is advertised all along
• Advertise subnets every 60 seconds during transit to new prefix

interface FastEthernet0/0
 description Inside - Advertise new prefix 21:26::1/64 recommission 2001:1::/64 
 ipv6 address 21:26::1/64
 ipv6 address 2001:1::/64 eui-64
 ipv6 nd prefix 2001:1::/64 at 12 Dec 2011 03:00 12 Dec 2011 02:59
 ipv6 nd ra interval 60