Neighbor Discovery Cisco IOS

Neighbors

Neighbor discovery. Mapping between IPv6 address and Link-layer Address. (MAC-address). Notice in the ouput below REACH means that the Node can be reached. STALE means the Node have not been reached the last 30 minuttes.

Showing Neighbors

Campus1#<input>show ipv6 neighbors</input>
IPv6 Address                              Age Link-layer Addr State Interface
FE80::216:76FF:FE9F:FEF6                    3 0016.769f.fef6  <notice>REACH</notice> Vl139
FE80::8555:196A:5ACC:1976                   4 0026.c7d3.5140  <notice>STALE</notice> Vl139
FE80::7AD6:F0FF:FE03:39A2                   5 78d6.f003.39a2  STALE Vl139
FE80::128C:CFFF:FE96:F76F                   4 108c.cf96.f76f  STALE Vl1
2001:16D8:DD85:139:9DAC:27C8:B159:1755      5 0024.d717.2b40  STALE Vl139
2001:16D8:DD85:139:20C:29FF:FE36:45B1       4 000c.2936.45b1  STALE Vl139
FE80::385E:C561:FCF9:7D57                   3 0050.568b.0004  STALE Vl139
FE80::6D18:8558:E775:3AA3                   0 b870.f473.0d6d  REACH Vl139
FE80::20C:29FF:FEBC:D8D7                    3 000c.29bc.d8d7  STALE Vl139
2001:16D8:DD85:139:B575:391E:D0EB:65F9      3 0050.568b.0008  STALE Vl139
FE80::14D0:4280:97DA:1817                   5 0024.2bce.819a  STALE Vl139
FE80::E570:A9A7:9163:7829                   0 1c4b.d676.6dc1  REACH Vl139
FE80::7DF9:81D5:2C78:70F3                   3 000c.2940.d4de  STALE Vl139
2001:16D8:DD85:139:754F:E641:1227:9D65      5 6c62.6d28.3cd2  STALE Vl139
<notice>...Output omitted...</notice>

Adding a static Neighbor entry

Some IPv6 traffic generators don't respond to ND - Neighbor Discovery.

R3(config)#<input>ipv6 neighbor  2001:16D8:DD85:140::77 fastethernet0/1 0010.dead.beef</input>
R3(config>#<input><CTRL-Z></input>
R3#<input>show ipv6 neighbors fastEthernet 0/1</input>
IPv6 Address                              Age Link-layer Addr State Interface
2001:16D8:DD85:140::77                      - 0010.dead.beef  REACH Fa0/1
</input>

Removing Neighbor entries

Removing all neighbors

Heimdal#<input>clear ipv6 neighbors</input>

Removing Neighbors on a specific Interface

Heimdal#<input>clear ipv6 neighbors gigabitEthernet 0/7</input>

Removing a specific Neighbor

Heimdal#<input>clear ipv6 neighbors gigabitEthernet 0/7 2001:fd56:5878:4::56fe</input>

NDP timer tuning

Heimdal#<input>show ipv6 interface vlan 28</input>
Vlan28 is up, line protocol is up
  IPv6 is enabled, link-local address is FE80::219:E7FF:FE51:8C9
  No Virtual link-local address(es):
  Description: TKUVLAN_308
  Global unicast address(es):
    2001:16D8:DD85:146::1, subnet is 2001:16D8:DD85:146::/64
  Joined group address(es):
    FF02::1
    FF02::2
    FF02::5
    FF02::6
    FF02::1:FF00:1
    FF02::1:FF51:8C9
  MTU is 1500 bytes
  ICMP error messages limited to one every 100 milliseconds
  ICMP redirects are enabled
  ICMP unreachables are sent
  Output features: Check hwidb
  ND DAD is enabled, number of DAD attempts: 1
  ND reachable time is 30000 milliseconds (using 35938)
  ND advertised reachable time is 0 (unspecified)
  ND advertised retransmit interval is 1000 milliseconds
  ND router advertisements are sent every 200 seconds
  ND router advertisements live for 1800 seconds
  ND advertised default router preference is Medium
  Hosts use stateless autoconfig for addresses.

NS-Interval

Neighbor Solicitation Interval

Time in milliseconds between solicitation messages between neighbors.

ICMPv6 type 135.

When searching for a neighbor this is the interval between packets. (Same as ARP requests in IPv4)

Default = 1000 mS (Select between 1000-172800000)

The NS-Interval is tranmitted as a ICMPv6 Router Advertisment to all nodes on the link. (To FF02::1)

R1(config)#<input>int fa0/0</input>
R1(config-if)#<input>ipv6 nd ns-interval 3000</input>

Reachable Time

Reachable-time

The amount of time in millisecondsthat a neighbor is considered reachable after an event that confirms its reachability.

Default = 30.000 Ms (Select between 0-3600000)

R1(config)#<input>int fa0/0</input>
R1(config-if)#<input>ipv6 nd reachable-time 10000</input>