CCNP Notes: IPv4 and IPv6 Coexistence

Posted by cmiller on February 15, 2011 Leave a comment (0) Go to comments

In the continuing series of CCNP notes, I am documenting my Cisco Certified Networking Professional (CCNP) studies and sharing my notes along the way. I am using the Official CCNP Route 642-902 exam guide from Cisco, available for purchase here.

This post covers notes from Chapter 18 regarding IPv4 and IPv6 Coexistence.

There are three ways to handle migration from IPv4 to IPv6

Dual IPv4/IPv6 stacks
Tunneling

Static Tunneling

Manually configured point-to-point
GRE

Dynamic Tunneling

IPv4 address of the receiving router is embedded in the IPv6 address, and as such the sending router is automatically able to determine the destination router’s address for the tunnel.
ISATAP: Uses 7th and 8th quartet to store IPv4 address
6to4: Uses 2nd and 3rd quartets to store IPv4 address

NAT Protocol Translator (NAT-PT)

Static Point-to-Point IPv6 Tunnels

Manually Configured Tunnels (MCT)

To plan

Find the IPv4 address for the tunnel and ensure that both routers can route to it. If loopback, ensure it’s in the IGP, for example.
Create the tunnel interface using the interface tunnel number command
Define the IPv4 tunnel source address: tunnel source {interface-type interface-number|ipv4-address}
Define the IPv4 tunnel destination: tunnel destination ipv4-address
Define the tunnel as a manually configured tunnel: tunnel model ipv6ip
Configure IPv6 address on the tunnel interface: ipv6 address address

The tunnel does not need an IPv4 address; it will use the source interface

Globally, enable IPv6 routing: ipv6 unicast-routing

To verify

show ipv6 interface brief
show ipv6 interface tunnel0

Link local is based on FF80::/96 plus 32-bits from IPv4 source address

General Routing Encapsulation (GRE)

To configure, follow same procedure as MCT, but use tunnel mode gre ip instead for tunnel mode.
The differences between GRE and MCT is:

GRE uses GRE packets to encapsulate
GRE MTU = 1476
MCT MTU = 1480

Link local is based on IPv6 EUI-64, using lowest numbered interface’s MAC address

Dynamic Multipoint IPv6 Tunnels

Use when irregular or infrequent traffic occurs between sites
The configuration steps can be less, but dynamic tunnels require more planning to follow set rules
These tunnels do not support IPv6 IGPs, requiring instead the use of static routes of multiprotocol BGP
6to4 Tunnels

First big decision point in design is to use globally unicast addresses or use private range (2002::/16)
If using private address range, the 2nd and 3rd quartet are the destination router’s (for the tunnel) IPv4 address (in hex)
To make this work, the sending router must have a multipoint tunnel setup and then configure a static route to send 2002::/16 out to the tunnel. This will trigger the logic on the tunnel to route to the correct place.
To configure

Configure loopback address and ensure its routable
Configure tunnel: interface tunnel number
Define the IPv4 tunnel source address: tunnel source {interface-type interface-number|ipv4-address}
DO NOT define a tunnel destination
Set tunnel mode to tunnel mode ipv6ip 6to4
Configure IPv6 address on the tunnel interface: ipv6 address address

The tunnel does not need an IPv4 address; it will use the source interface

Globally, enable IPv6 routing: ipv6 unicast-routing
Define a static route for 2002::/16 to trigger tunnel routing

To use globally unicast addresses, simply setup the tunnels using the 2002::/16 logic and define the IPv4 of the destination router for the tunnel in the 2002::/16 address, making sure to add a static route to the 2002::/16 subnet. This will trigger a recursive lookup for tunnel0 and cause the to4 logic to apply, deriving the IPv4 destination address again from the 2nd and 3rd quartet.

ISATAP Tunnels

Much the same of 6to4 tunnels, but use globally unicast addresses.
Uses modified EUI-64 to determine the address:

Configure a 64-bit prefix on the tunnel interface, and use the eui-64 parameter, telling the router to derive its own interface ID.
The router adds 0000:5EFE to the 5th and 6th quartet
The router finds the tunnel’s source IPv4 address and uses the hex conversion for the 7th and 8th quartet

To configure

Configure loopback address and ensure its routable
Configure tunnel: interface tunnel number
Define the IPv4 tunnel source address: tunnel source {interface-type interface-number|ipv4-address}
DO NOT define a tunnel destination
Set tunnel mode to tunnel mode ipv6ip isatap
Configure an IPv6 prefix using ipv6 address prefix/length eui-64
Globally, enable IPv6 routing: ipv6 unicast-routing
Define a static route for the destination networks with an outgoing interface and next-hop address.