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IPv6 (NETS notes)

Pete Siemsen
last updated 2012-11-27 by Pete Siemsen


As of 2012-11-27, IPv6 is established in all three FRGP routers, and about half of the FRGP members have established IPv6 peering with the FRGP. In UCAR, test VLAN 63 at ML is dual-stack and serves Pete's and John's office machines. VLAN 206 at FL was established an RAL's request, but seems lightly used. GLOBE has requested an IPv6 VLAN for its web servers.

NETS has discussed wider deployment of IPv6 in UCAR, but hasn't made much progress yet.

IPv6 Addressing Plan for UCAR

This section describes a proposed IPv6 addressing structure for UCAR. IPv6 addresses consist of 128 bits (16 bytes). It is convenient to discuss the 128 bits as a 64-bit "top" half and a 64-bit "bottom" half.

The top 64 bits

RFC 3587 is a good place to start. It defines the format of IPv6 global unicast addresses as follows. I've added rows to show 2001:468:500::/40, the range that Internet2 allocated to the FRGP. See FRGP IPv6 Address Space Delegations

Top 64 bits of IPv6 addresses
2001:468:500::/40 allocated to the FRGP by Internet2  
2001:468:503::/48 allocated to UCAR by the FRGP  
48 bits 16 bits
global routing prefix subnet ID
20 01 04 68 05 03 xx xx
00100000 00000001 00000100 01101000 00000101 00000011 ssssvvvv vvvvvvvv

We can use the top 4 bits of the "subnet ID" as a UCAR site id and the bottom 12 bits as a VLAN id. This provides for up to 16 sites and 4096 VLANs. For now, we could use the IPv4 subnet number already in use on the VLAN as the VLAN id, simply because it provides a unique scheme that is easy to understand. With this scheme, when a human reads an IPv6 address, the site id and VLAN id can be "seen". This might ease the handling of IPv6 addresses.

Site IDs might be:
SiteUCAR Site ID
Mesa Lab1
Foothills Lab2
Center Green3

The bottom 64 bits: the EUI-64 part

UCAR IPv6 example: A Dell PC with MAC address 00:06:5b:87:69:bf at the Foothills Lab (UCAR site 2) in MMM's VLAN 88 (hex 58) would have the IPv6 address 2001:468:503:2058:6:5bff:fe87:69bf, as follows:

UCAR PRT Prefix SLA ID 64-bit EUI-64 Interface ID
 20   01   04   68   05   03   2  58   00   06   5b   ff   fe   87   69   bf 


You might assume that DNS for IPv6 involves special new IPv6 DNS servers. Actually, DNS for IPv6 uses the same DNS servers as those for IPv4. The DNS servers should be "dual-stacked" so that they accept IPv4 packets or IPv6 packets.

UCAR's existing DNS servers can be configured to resolve IPv6 names and addresses. For example, they could resolve into 2001:468:503:009::2a0:a5ff:fe12:5b43 and vice versa. DNS requests could arrive at the DNS servers in IPv4 or IPv6 packets, and the DNS servers would respond using the protocol of the request. Thus, IPv4 and IPv6 hosts could resolve both IPv4 and IPv6 names and addresses.

Host Autoconfiguration

When an IPv6 host boots, it asks the local router for part of it's IPv6 address. This is called Autoconfiguration or Neighbor Discovery. The router supplies the first 64 bits of the IPv6 address, which specifies the globally unique part and the VLAN-specific part. The host supplies the second 64 bits, which is unique to the host. For this to work, the router must be configured to advertise the first 64 bits of the addresses used on each VLAN.

UCAR IPv6 subnets

To implement IPv6 in the UCAR network, I'll have to define an IPv6 subnet "next to" each IPv4 subnet. Demand is nonexistent, so there's no reason to do this on every UCAR network. I'll only do it on UCAR router interfaces connected to networks that have IPv6 hosts. Initially, I'll do the .2. subnet so the network monitor can monitor IPv6, and the .8. subnet for testing (my laptop). Then I'll use OSPFv3 to distribute IPv6 in UCAR, as it does for IPv4 today.

Monitoring IPv6

As of 2009-01-12, we don't monitor IPv6. Back in 2003, Vince Biondolillo of UCB ran a Perl script that pinged various FRGP IPv6 addresses and sent email to me when something doesn't respond. Vince has left UCB and his script no longer runs.

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