Hurricane Electric's IPv6 Tunnel Broker Forums

General IPv6 Topics => IPv6 on Windows => Topic started by: NCFTA on March 22, 2010, 01:07:18 PM

Title: prefix overlaps error cisco ios
Post by: NCFTA on March 22, 2010, 01:07:18 PM
I have a cisco 2611 I previously configured to route site local IPv6 traffic.  I used the FEC:: site local prefix with eui-64 and stateless auto-config to configure my interfaces. I was just routing between VLANs on my LAN.   (All my boxes are linux, and I'm using a cisco catalyst switch to do the vlans.)  Everything was routing properly.

I then registered and setup a tunnel using the example for cisco ios from h.e.  That seemed to go fine.  To assign from the /64 block listed in my new tunnel "tunnel details" (since I don't have a dhcp6 server up yet), I did a static assignment on one of my router interfaces using the /64 prefix and eui-64.  On the first interface it went ok, and automatically filled in the last 64 bits. Then the other hosts on the vlan connected to the interface auto-configured new global unicast addresses from the same /64 prefixes.

But on the subsequent interfaces I get error "overlaps with another prefix".  I tried doing static addresses from the /64 block instead of eui-64, for example ::1/64, ::2/64 and got the same message.

What am I doing wrong? Is there something I don't understand about how to use the /64 block from Hurricane Electric?  Thanks.

Title: Re: prefix overlaps error cisco ios
Post by: jimb on March 22, 2010, 01:31:19 PM
You're using a /64 on more than one LAN.  You need to allocate a /48 and break /64s out from that.

Example:

2001:db8:1234::/48

LAN0: 2001:db8:1234::/64
LAN1: 2001:db8:1234:1::/64
LAN2: 2001:db8:1234:2::/64
...
Title: Re: prefix overlaps error cisco ios
Post by: NCFTA on March 22, 2010, 02:17:31 PM
You're using a /64 on more than one LAN.  You need to allocate a /48 and break /64s out from that.

Example:

2001:db8:1234::/48

LAN0: 2001:db8:1234::/64
LAN1: 2001:db8:1234:1::/64
LAN2: 2001:db8:1234:2::/64
...

Thanks.