IPv6 Routing Table

flutteringevergreenNetworking and Communications

Oct 29, 2013 (4 years and 10 days ago)

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IPv6 Routing

IPv6 Routing

2

Describing IPv6 Routing

IPv6 Routing

3

IPv6 Routing Table


IPv6 routing protocols still use the longest
-
match
prefix as the oruting algorithm for route selection as
their equivalent did in IPv4.


Ipv6 routing table is handled and managed
separately from the IPv4 routing table when both
protocols are enabled simultaneously.


IPv6 unicast
-
routing


Enabled on Cisco routers

router start forwarding
IPv6 packets between its interfaces using IPv6
routing table.


IPv6 Routing

4

Administrative Distance


Administrative distance remains same as in IPv4 as displayed
by the following table:

IPv6 Routing

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Displaying IPv6 Routing Table

Following addresses
are automatically
inserted in the routing
table:

Multicast
-
prefix

Link
-
local prefix

Default ipv6 route

Static Routing

IPv6 Routing

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Static Routing Overview


Static routes are manually configured and define an
explicit path between two networking devices.


Restrictions for Implementing Static Routes for IPv6:


IPv6 static routes do not currently support the

tag

and
permanent

keywords of the IPv4 ip route command.


IPv6 does not currently support inserting static routes into
virtual routing and forwarding (VRF) tables.

IPv6 Routing

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Static IPv6 Routes


Prerequisite for static IPv6 routes:


Before configuring the router with a static IPv6 route:


Enable forwarding of IPv6 packets using the
ipv6 unicast
-
routing

global configuration command


enable IPv6 on at least one interface


configure an IPv6 address on that interface.


Static routes are useful for smaller networks with only one
path to an outside network and to provide security for a
larger network for certain types of traffic or links to other
networks that need more control.


Types of static routes

1.
Directly attached static routes

2.
Fully specified static routes

3.
Floating static routes


IPv6 Routing

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Directly Attached Static Routes


In directly attached static routes, only the output interface
is specified.


The destination is assumed to be directly attached to this
interface, so the packet destination is used as the next hop
address.


ipv6 route 2001:0DB8::/32 ethernet1/0


all destinations with address prefix 2001:0DB8::/32 are
directly reachable via interface Ethernet1/0.


Directly attached static routes are candidates for insertion
in the IPv6 routing table only if they refer to a valid IPv6
interface; that is, an interface that is both up and has IPv6
enabled on it.

IPv6 Routing

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Fully Specified Static Routes


Both the
output interface

and the
next hop

are
specified.


This form of static route is used when the output
interface is a multi
-
access one and it is necessary to
explicitly identify the next hop.


The next hop must be directly attached to the
specified output interface.


ipv6 route 2001:DB8:/32 ethernet1/0 2001:0DB8:3000:1



A fully specified route is valid (that is, a candidate for
insertion into the IPv6 routing table) when the specified
IPv6 interface is IPv6
-
enabled and up.

IPv6 Routing

11

Floating Static Routes


Floating static routes are static routes that are used to back up
dynamic routes learned through configured routing protocols.


A floating static route is configured with a higher administrative
distance than the dynamic routing protocol it is backing up.


As a result, the dynamic route learned through the routing
protocol is always used in preference to the floating static route.


If the dynamic route learned through the routing protocol is lost,
the floating static route will be used in its place.


ipv6 route 2001:DB8:/32 ethernet1/0 2001:0DB8:3000:1 210


Any of the three types of IPv6 static routes can be used as a
floating static route.



Note: By default, static routes have smaller administrative distances
than dynamic routes, so static routes will be used in preference to
dynamic routes.


IPv6 Routing

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Implementing Static Routes for IPv6

1.

Configuring a Static IPv6 Route

IPv6 Routing

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Examples


Directly Attached Static Route through Point
-
to
-
Point
Interface


Router(config)# ipv6 route 2001:0DB8::/32 serial 0



Directly Attached Static Route on Broadcast
Interface


Router(config)#

ipv6 route 2001:0DB8::1/32 ethernet1/0


Fully Specified Static Route on Broadcast Interface


Router(config)# ipv6 route 2001:0DB8::1/32 ethernet1/0
fe80::1

IPv6 Routing

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Configuring a Floating Static IPv6
Route


STEPS

1.
enable


2.
configure

terminal


3.
ipv6 route

ipv6
-
prefix
/
prefix
-
length

{
ipv6
-
address

|
interface
-
type interface
-
number
[
ipv6
-
address
]}
[
administrative
-
distance
] [
administrative
-
multicast
-
distance

|
unicast

|
multicast
] [
tag

tag
]

IPv6 Routing

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Verifying Static IPv6 Route
Configuration and Operation


show ipv6 static


To display a set of static routes and the installed status of each,
that is, whether an entry for each route appears in the IPv6
routing table.


show ipv6 route


To confirm that installed routes are in the IPv6 routing table and
that each route definition reflects the expected cost and metric.


If a static route that you have configured does not appear in the IPv6
routing table, it is possible that there is a lower administrative
distance from another source in the table, such as from a routing
protocol.


If a lower administrative distance exists, the static route is "floating"
and will be inserted into the routing table only when the route learned
through the routing protocol disappears. I

IPv6 Routing

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show ipv6 static


Router# show ipv6 static

IPv6 Static routes

Code: *
-

installed in RIB

* 2001:0DB8:3000:0/16, interface Ethernet1/0, distance 1

* 2001:0DB8:4000:0/16, via nexthop 2001:0DB8:1:1, distance 1


2001:0DB8:5000:0/16, interface Ethernet3/0, distance 1

* 2001:0DB8:5555:0/16, via nexthop 2001:0DB8:4000:1, distance 1


2001:0DB8:5555:0/16, via nexthop 2001:0DB8:9999:1, distance 1

* 2001:0DB8:5555:0/16, interface Ethernet2/0, distance 1

* 2001:0DB8:6000:0/16, via nexthop 2001:0DB8:2007:1, interface
Ethernet1/0, distance 1



Implementing OSPF
for IPv6

OSPFv3

IPv6 Routing

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Similarities Between OSPFv2 and
OSPFv3

IPv6 Routing

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Prerequisites for Implementing
OSPF for IPv6


Before you enable OSPF for IPv6 on an interface,
you must do the following:


Complete the OSPF network strategy and planning for your
IPv6 network. For example, you must decide whether
multiple areas are required.


Enable IPv6 unicast routing.


Enable IPv6 on the interface.


Configure the IP Security (IPSec) secure socket application
program interface (API) on OSPF for IPv6 in order to
enable authentication and encryption.

IPv6 Routing

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Differences Between OSPFv2 and
OSPFv3


In OSPF for IPv6, a routing process does not need to be
explicitly created.


Enabling OSPF for IPv6 on an interface will cause a routing
process, and its associated configuration, to be created.


In OSPF for IPv6, each interface must be enabled using
commands in interface configuration mode.


This feature is different from OSPF version 2, in which
interfaces are indirectly enabled using the router
configuration mode
.


Some of the notable changes include:


platform
-
independent implementation


protocol processing per
-
link rather than per
-
node


explicit support for multiple instances per link


changes in authentication and packet format

IPv6 Routing

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Differences Between OSPFv2 and
OSPFv3


OSPFv3 runs over a link



IPv6 uses the term
link
to indicate a
communication facility or
medium over

which nodes can communicate at the link layer


OSPF interfaces connect to
links

instead of to
IP subnets
.


OSPF for IPv6 therefore runs
per
-
link
instead of the IPv4 behavior
of
per
-
IP
-
subnet
, and the terms
network

and
subnet

are generally
replaced by the term
link
.


This change affects the receiving of OSPF protocol packets, and
the contents of hello packets and network LSAs.

IPv6 Routing

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Differences Between OSPFv2 and
OSPFv3


Link
-
local addresses are used


OSPFv3 uses IPv6 link
-
local addresses to identify
the OSPFv3 adjacency neighbors.


When configuring the
ipv6 ospf neighbor

command, the IPv6 address used must be the
link
-
local address of the neighbor.


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Differences Between OSPFv2 and
OSPFv3


Multiple OSPFv3 instance support



Separate autonomous systems, each running OSPF, use a common
link.


A single link could belong to multiple areas.


OSPFv3 uses a new field, called the
Instance ID, to allow multiple
instances per link.



To have two instances talk to each other, they must share the same
instance ID.


By default, the instance ID is set to 0.


Multicast addresses



FF02::5


Represents all shortest path first (SPF) routers on the link
-
local scope, equivalent to
224.0.0.5

in OSPFv2.


FF02::6


Represents all designated routers (DRs) on the link
-
local
scope, equivalent to
224.0.0.6

in OSPFv2.

IPv6 Routing

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New LSA Types for IPv6


Link LSAs (Type 8)


Have local
-
link flooding scope and are never flooded beyond the
link with which they are associated.


Link LSAs provide the link
-
local address of the router to all other
routers attached to the link, inform other routers attached to the
link of a list of IPv6 prefixes to associate with the link, and allow
the router to assert a collection of Options bits to associate with
the network LSA that will be originated for the link.

IPv6 Routing

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New LSA Types for IPv6


Intra
-
Area
-
Prefix LSAs (Type 9)


A router can originate multiple intra
-
area
-
prefix LSAs for
each router or transit network, each with a unique link
-
state
ID.


The link
-
state ID for each intra
-
area
-
prefix LSA describes
its association to either the router LSA or the network LSA
and contains prefixes for stub and transit networks.


Implementing and
Verifying OSPFv3

IPv6 Routing

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IPv6 Configuration


Before configuring OSPFv3, IPv6 must be enabled
with the
ipv6 unicast
-
routing

global configuration
command.


Use the
ipv6 address

address
/
prefix
-
length

[
eui
-
64
]
interface configuration

command to configure an
IPv6 address for an interface and enable IPv6
processing on the interface.


The
eui
-
64

parameter forces the router to complete
the addresses' low
-
order 64
-
bits using an EUI
-
64
format interface ID.


IPv6 Routing

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Steps to Configure OSPF for IPv6

1.
Complete the OSPF network strategy and planning for your
IPv6 network. For example, you must decide whether multiple
areas are required.

2.
Enable IPv6 unicast routing using the
ipv6 unicast
-
routing

command.

3.
Enable IPv6 on the interface using the
ipv6 ospf area

command.

4.
(Optional) Configure OPSFv3 interface specific settings,
including area, router priority, and OSPFv3 path cost.

5.
(Optional) Configure routing specifics from router configuration
mode, including router priority, route summarization, and so on.

IPv6 Routing

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Enabling OSPFv3 on an Interface


Most of the OSPFv3 configuration is done on
the interface.

IPv6 Routing

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Configuring OSPFv3 Routing Specifics



OSPFv3 routing specifics are configured from router
configuration mode.


For an IPv6
-
only router, a router ID parameter must be defined in the
OSPFv3 configuration as an IPv4 address using the
router
-
id

router
-
id

router configuration command.


OSPFv3 uses a 32
-
bit number for a router ID.


The OSPFv3 router ID can be expressed in dotted decimal, allowing
easy overlay of an OSPFv3 network on an existing OSPFv2 network.


If IPv4 is configured on the router, by default, the router ID is chosen in
the same way as it is with OSPFv2.


The highest IPv4 address configured on a loopback interface becomes
the router ID.



If no loopback interfaces are configured, the highest address on any
other interface becomes the router ID.

IPv6 Routing

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OSPFv3 Route Summarization

Before Summarization:

After Summarization:

IPv6 Routing

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OSPFv3 Configuration Example

IPv6 Routing

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OSPFv3 Configuration Example

The following example configures an OSPF routing process 109 to run on the
interface and puts it in area

1:

ipv6 ospf 109 area 1

IPv6 Routing

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Verifying OSPFv3

IPv6 Routing

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Verifying OSPFv3 Neighbors

IPv6 Routing

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Verifying OSPFv3 Database

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Lab Exercises


Configuring OSPF for IPv6


Case
-
study Configuring Static Routes and
Routing Protocols with Cisco