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IPv6 Global Prefix RA question from R1 to R2

linocatucci
Level 1
Level 1

Hello,

I've a questiona about IPv6 Global Prefix RA.

I have 2 routers (r1 and r2) connected via fastethernet0/0 interface.

On the first router i have gone trough the ipv6 set up:

1. I have create a ipv6 address: #ipv6 address 2001:aaa:bbbb:cccc::/64 eui-64

2. told the router that it can route ipv6: #ipv6 unicast-routing

Below is a #show ipv6 interface on R1:

FastEthernet0/0 is up, line protocol is up

  IPv6 is enabled, link-local address is FE80::CA00:10FF:FE84:0

  Global unicast address(es):

    2001:AAA:BBBB:CCCC:CA00:10FF:FE84:0, subnet is 2001:AAA:BBBB:CCCC::/64

  Joined group address(es):

    FF02::1

    FF02::2

    FF02::1:FF84:0

On the second router I have gone trough the ipv6 steps:

1. I have enable ipv6: #ipv6 enable.

I do see that the link-local address has been created: FE80::CA02:10FF:FE84:0

Below is a # show ipv6 interface on R2:

FastEthernet0/0 is up, line protocol is up

  IPv6 is enabled, link-local address is FE80::CA02:10FF:FE84:0

  No global unicast address is configured

  Joined group address(es):

    FF02::1

    FF02::2

    FF02::1:FF84:0

My question is as follows: why doesn't get Router2 the global prefix information in the ipv6 address from Router 1

I do see a RA send from R1 to R2.

R1#

*Mar  1 00:40:37.455: ICMPv6-ND: Sending RA to FF02::1 on FastEthernet0/0

*Mar  1 00:40:37.455: ICMPv6-ND:     MTU = 1500

*Mar  1 00:40:37.455: ICMPv6-ND:     prefix = 2001:AAA:BBBB:CCCC::/64 onlink autoconfig

*Mar  1 00:40:37.455: ICMPv6-ND:             2592000/604800 (valid/preferred)

*Mar  1 00:40:37.455: IPV6: source FE80::CA00:10FF:FE84:0 (local)

*Mar  1 00:40:37.455:       dest FF02::1 (FastEthernet0/0)

*Mar  1 00:40:37.455:       traffic class 224, flow 0x0, len 104+1396, prot 58, hops 255, originating

*Mar  1 00:40:37.455: IPv6: Sending on FastEthernet0/0

R2(config)#

*Mar  1 00:39:42.275: ICMPv6-ND: Received RA from FE80::CA00:10FF:FE84:0 on FastEthernet0/0

What I also see is that R1 is getting RA from R2:

R1#

*Mar  1 00:47:56.199: ICMPv6-ND: Received RA from FE80::CA02:10FF:FE84:0 on FastEthernet0/0

Thank I great advance,

Lino

3 Replies 3

Hi Lino ,

have you tried on Fa0/0 on R2 : ipv6 address autoconfig.

Dan

Nagendra Kumar Nainar
Cisco Employee
Cisco Employee

Hi Lino,

My question is as follows: why doesn't get Router2 the global prefix  information in the ipv6 address from Router 1

You need to configure "ipv6 address autoconfig". When you have it enabled, IPv6 router on receiving RA will get the prefixes with A flag set and will append 64 bit Interface ID.

What I also see is that R1 is getting RA from R2:

Per my understanding, RA is not only for stateless autoconfiguration. SLAAC is one benefit from RA while there are otehr benefits like MAC learning, default router advertisement etc..

Thanks,

Nagendra

Thanks Naikumar.

ipv6 address autoconfig did the trick

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