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CCIE IPv6
review questions for IPv6
64
Computer Networking
04/15/2010

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Term
How does IPv6 host learn its addresses when using Stateless Autoconfig?
Definition

1) Host generates link-local address (FE:80:: + EUI-64)

2) Host sends Neighbor Solicitation to solicited node multicast address (FF02::1::ff + last 24 bits of mcast address)

3) Host sends router solicitation (RS) to FF02::2 (all routers) to get global prefix, etc.

Term
How does IPv6 host learn its addresses when using Stateful Autoconfig?
Definition

1) Router Advertisement (RA) has M-bit set

2) Host sends DHCP request to FF02::1:2 or FF02::1:3, UDP port 547

3) DHCP server assigns full 128-bit address.

Term
What are multicast scopes and how are the indicated in IPv6 addresses?
Definition

Mcast address format : FF.[4 bits lifetime][4 bits scope]

 

Scope bits are as follows:

 

Node -- 0001

Link -- 0010

Site -- 0101

Org -- 1000

Global -- 1110

 

Example: FF02 -- permanent lifetime, link scope

Term
What is the EUI-64 address for a device with the MAC address 0000.0c0a.2c51?
Definition
0000.0c0a.2c51
->
0200:0cff:fe0a:2c51

(flip universal local bit, insert fffe after MAC OUI)
Term
For global unicast addresses, how many bits are available for an organization's subnets (site-level aggregator bits)?
Definition

16 bits

 

 

45 bits

16 bits

64 bits

001

Global Routing Prefix

Site Level Aggregator

EUI-64

Term
How often are Router Advertisements sent?
Definition
200 seconds
Term
What is the link-local address?
Definition
FE80::/10 + EUI-64 address
Term
How is an embedded RP indicated in a multicast packet?
Definition
Multicast address begins with FF7::/12
Term
What IPv6 addresses does a host need to know?
Definition
Link-local
Assigned unicast
Loopback address
All-nodes multicast (FF02::1)
Solicited node multicast for all unicast and anycast addresses.
Multicast address of all groups to which host belongs.
Term
What is the solicited-node multicast-address? What is it used for?
Definition

FF02::1:F + last 24 bits of IPv6 address/104

 

Used for Neighbor discovery using the Neighbor Solicitation message.

Term
What is the MLD equivalent of an IGMP Leave?
Definition
MLD Done
Term
What is the MAC address of an IPv6 multicast packet?
Definition
33-33 + last 32 bits of multicast address
Term
What is Neighbor Solicitation used for?
Definition
Duplicate Address Detection
Learning Link-Layer Addresses
Determine if Neighbor is reachable
Term
True or False:
ICMPv6 packets must be rate-limited
Definition
True.
Default is 100 msec error-interval with token bucket size of 10 (1 token = 1 ICMPv6 message)
Term
What is FF02::1?
Definition
FF02::1 = well known multicast address for all nodes
Term
What is the v6 multicast address for an OSPF speaker?
Definition
FF02::5
Term
What is the v6 multicast address for OSPF DR/BDR?
Definition
OSPF DR/BDR = FF02::6
Term
What is FF02::A used for?
Definition
v6 EIGRP
Term
What is FF02::D for?
Definition
all v6 PIM routers
Term
What is the MAC address of an IPv6 multicast packet to ff02::1:ff98:0?
Definition
33:33:ff:98:00:00
Term
What is the function of the Traffic Class field in the v6 header?
Definition
Traffic class is the equivalent to IPv4 DSCP
Term
What 3 commands are needed to enable IPv6?
Definition

ipv6 cef

ipv6 unicast-routing

 

interface e0

 ipv6 enable

Term
What does a host do when it wants to join a IPv6 multicast group?
Definition
Host sends an MLD Report to group address.
Term
What is IGMP equivalent of MLD v1?
Definition
MLD v1 => IGMPv2


MLD v2 => IGMPv3
Term
What does an IPv6 multicast router do when it receives an MLD Done?
Definition
Router sends a multicast-address-specific Query to see if anyone else is interested.
Term
What multicast protocols does IPv6 support?
Definition
SM, BIDIR, SSM
Term
Why might you configure this:
ipv6 route ::/0 tunnel0 multicast
Definition
This is an IPv6 mroute that can help with RPF problems in tunnels.
Term
Name 3 functions ICMPv6 provides
Definition
1) Error Reporting
2) MTU Path Discovery
3) Neighbor Discovery
Term
Name errors that ICMPv6 can report
Definition
1) Packet too big
2) Hop Limit Exceeded
3) Bad Header
4) Unrecognized Option
5) No Route to Destination
6) Access Prohibited
7) Port Unreachable
Term
Is ICMPv6 rate-limited by default?
Definition
Yes, default is 100 ms error-interval with token bucket size of 10 tokens (ICMP messages)
Term
How often does a router send Router Advertisements by default and to what address?
Definition
Every 200 seconds to FF02::1

In response RS, can be sent to unicast address.
Term
What provides the v6 equivalent of ARP?
Definition
Neighbor Solicitation
Term

Where is the following configured and what will happen to addresses that match the ACL?

 

ipv6 verify unicast reverse-path <ACL>

Definition

This is configured per-interface:

(config-if)#ipv6 verify unicast reverse-path <ACL>

 

Packets permitted by ACL will be exempt from uRPF checks.

Term
What are the 5 IPV6 neighbor reachability states?
Definition

Incomplete (NS sent, no NA)

Reachable

Stale

Delay

Probe - send 3 @ 1 second, remove entry if no response

Term
What are AAAA records used for?
Definition
IPv6 DNS
Term
What is the command to apply a v6 ACL to an interface?
Definition
interface f0/0
ipv6 traffic-filter in
Term
How do you apply a v6 ACL to VTYs?
Definition

line vty 0 4

 access-class <v6 ACL> in

Term
What is the AD of a static route in IPv6?
Definition
1
Term
Where are Type 8 LSAs flooded?
Definition
Local link only
Term
What LSA contains prefix information for the area in OSPFv6?
Definition
Type 9 (Intra-Area Prefix) LSA maps prefixes to Router LSAs and Network LSAs
Term
Is there a default v6 OSPF RID?
Definition
No, must have an IPv4 address on some interface OR explicitly configure RID.
Term
What authentication types are supported in OSPFv3?
Definition

OSPFv3 relies on IPv6 mechanisms.

(config-if)#ipv6 ospf authentication  -- AH

(config-if)#ipv6 ospf encryption -- ESP

Term
How are areas assigned in OSPFv3?
Definition

On the interface:

 

interface E0

 ipv6 enable

 ipv6 ospf 100 area 0

Term
If an OSPFv3 adjacency is not forming on a Frame Relay Link, what might be wrong?
Definition
OSPFv3 needs a FR map statement for the link local AND the unicast address
Term
What address is used for the "ADV Router" in OSPFv3?
Definition
ADV Router is the RID of the advertising router -- the v4-formatted RID!
Term
Can EIGRPv6 do classful routing?
Definition
No. no-auto-summary cannot be disabled in v6 EIGRP.
Term
Name 5 features that IPv6 QoS does not support.
Definition
Not supported in IPv6:
NBAR
cRTP
CAR
PQ
CQ
Term
How do you do route filtering in EIGRP v 6?
Definition

Distribute lists with prefix-lists:

ipv6 router eigrp 100

 distribute-list prefix-list MYLIST in Serial1

Term
What tunneling method would you use to connect isolated IPv6 islands over an IPv4 network?
Definition
Automatic 6 to 4
Term
What is the reserved address space for 6to4 tunnels?
Definition
2002::/16
Term
How does a 6to4 tunnel know the IPv4 destination for a packet to 2002:c0a8:6501::1?
Definition
The IPv4 destination is extracted from the v6 address: 2002:c0a8:6501::1 -> c0a8:6501 -> 192.168.101.1
Term
What tunnel type connects isolated v6 hosts in a single site?
Definition
ISATAP
Term
What kind of address is the following? What do the last 4 octet represent?
2001:DB8:1234:5678:0000:5EFE:0AAD:8108
Definition
IPv6 ISATAP tunnel address.

0AAD:8108 = 10.173.129.8 = IPv4 address of this interface
Term
How are RAs handled in ISATAP tunnels?
Definition
RAs are suppressed by default in ISATAP tunnels. Enable them with "no ipv6 nd suppress-ra"
Term
What v6 tunnel types are point to multi-point?
Definition
6to4 (inter-site)
ISATAP (intra-site)
Term
Why are 6to4 and ISATAP tunnels configured without a "tunnel destination"?
Definition
Because the v4 tunnel destination is derived dynamically for each packet (from the v6 address).
Term
How is the embedded IPv4 address different in 6to4 vs ISATAP?
Definition
In 6to4, the IPv4 address comes right after 2002::/16 reserved prefix.

In ISATAP, the v4 address comes at the end of the v6 address, right after 0000:5EFE.
Term
Which address pool do v6 anycast addresses come from?
Definition
Unicast.
Term
What command limits the level of syslog messages sent to syslog servers?
Definition
Router(config)# logging trap level

Limits the number of messages logged to the syslog servers.
(Logging trap is a trap because it makes you think SNMP when it's not).
Term
Which mechanism in IPv6 is responsible for Layer 3 to Layer 2 address resolution?
Definition
NDP (Neighbor Discovery Protocol)
Term
How many bits make up the Group ID in IPv6 multicast?
Definition
Group ID = 112 bits
Term
What IPv6 header field can perform the same functions as the IPv4 protocol field?
Definition
Next Header
Term
Name 4 QoS features that are supported with IPv6
Definition
MQC policing
MQC shaping
MQC marking
WRED
Term
How can you configure an IPv6 router with a higher preference when hosts get multiple RA responses?
Definition
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