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

<source lang=cli> 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.

</input>

NS-interval

Neighbor Solicitation Interval

Time in milliseconds between solicitation messages between neighbors.