01-08-2012 06:51 PM - edited 03-07-2019 04:13 AM
hi everybody.
how is everyone doing?
Please consider the following scenario:
R1 f0/0---------------f0/0 R2
Both routers are ipv6-enabled
R2#show ipv6 int brief
FastEthernet0/0 [up/up]
FE80::C201:CFF:FE98:0
2000::2
R1#show ipv6 int brief
FastEthernet0/0 [up/up]
FE80::C200:CFF:FE98:0
2000::1
Below is wireshark captured packet was transmitted by r1 to or r2 .
No. Time Source Destination Protocol Length Info
2 0.297000 :: ff02::1:ff98:0 ICMPv6 78 Neighbor Solicitation for fe80::c200:cff:fe98:0
Below is the expanded fields of the above packet:
Frame 2: 78 bytes on wire (624 bits), 78 bytes captured (624 bits)
Ethernet II, Src: c0:00:0c:98:00:00 (c0:00:0c:98:00:00), Dst: IPv6mcast_ff:98:00:00 (33:33:ff:98:00:00)
Internet Protocol Version 6, Src: :: (::), Dst: ff02::1:ff98:0 (ff02::1:ff98:0)
Internet Control Message Protocol v6
Type: Neighbor Solicitation (135)
Code: 0
Checksum: 0xadf6 [correct]
Reserved: 00000000
Target Address: fe80::c200:cff:fe98:0 (fe80::c200:cff:fe98:0)
What is router trying to do? is it trying to verify the link local adress fe80::c200:cff:fe98:0 not being used by some other ipv6 node?
==============================
After a while, R1 sends a packet which is shown below:
No. Time Source Destination Protocol Length Info
6 1.078000 :: ff02::1:ff00:1 ICMPv6 78 Neighbor Solicitation for 2000::1
Frame 6: 78 bytes on wire (624 bits), 78 bytes captured (624 bits)
Ethernet II, Src: c0:00:0c:98:00:00 (c0:00:0c:98:00:00), Dst: IPv6mcast_ff:00:00:01 (33:33:ff:00:00:01)
Internet Protocol Version 6, Src: :: (::), Dst: ff02::1:ff00:1 (ff02::1:ff00:1)
Internet Control Message Protocol v6
Type: Neighbor Solicitation (135)
Code: 0
Checksum: 0x5aa6 [correct]
Reserved: 00000000
Target Address: 2000::1 (2000::1)
Is R1 trying to verify 2000::1 i not being used by any other ipv6 node?
=========================================================
R1 transmits the following packet to R2
No. Time Source Destination Protocol Length Info
7 1.391000 fe80::c200:cff:fe98:0 ff02::16 ICMPv6 90 Multicast Listener Report Message v2
Below is the expanded field of the above packet:
Frame 7: 90 bytes on wire (720 bits), 90 bytes captured (720 bits)
Ethernet II, Src: c0:00:0c:98:00:00 (c0:00:0c:98:00:00), Dst: IPv6mcast_00:00:00:16 (33:33:00:00:00:16)
Internet Protocol Version 6, Src: fe80::c200:cff:fe98:0 (fe80::c200:cff:fe98:0), Dst: ff02::16 (ff02::16)
Internet Control Message Protocol v6
Type: Multicast Listener Report Message v2 (143)
Code: 0
Checksum: 0xa2d8 [correct]
Reserved: 0000
Number of Multicast Address Records: 1
Multicast Address Record Changed to exclude: ff02::1:ff98:0
Record Type: Changed to exclude (4)
Aux Data Len: 0
Number of Sources: 0
Multicast Address: ff02::1:ff98:0 (ff02::1:ff98:0)
What is the purpose of this packet?
Thanks and have a great day.
Solved! Go to Solution.
01-12-2012 07:28 AM
Hi Sarah,
Frame 2: 78 bytes on wire (624 bits), 78 bytes captured (624 bits)
Ethernet II, Src: c0:00:0c:98:00:00 (c0:00:0c:98:00:00), Dst: IPv6mcast_ff:98:00:00 (33:33:ff:98:00:00)
Internet Protocol Version 6, Src: :: (::), Dst: ff02::1:ff98:0 (ff02::1:ff98:0)
Internet Control Message Protocol v6
Type: Neighbor Solicitation (135)
Code: 0
Checksum: 0xadf6 [correct]
Reserved: 00000000
Target Address: fe80::c200:cff:fe98:0 (fe80::c200:cff:fe98:0)
What is router trying to do? is it trying to verify the link local adress fe80::c200:cff:fe98:0 not being used by some other ipv6 node?
Yes. The router is performing Duplicate Address Detection (DAD) on its link-local address. While the link-local addresses are usually automatically assigned and derived from MAC addresses, they are nevertheless configurable and are subject to DAD just like any other IPv6 address.
Frame 6: 78 bytes on wire (624 bits), 78 bytes captured (624 bits)
Ethernet II, Src: c0:00:0c:98:00:00 (c0:00:0c:98:00:00), Dst: IPv6mcast_ff:00:00:01 (33:33:ff:00:00:01)
Internet Protocol Version 6, Src: :: (::), Dst: ff02::1:ff00:1 (ff02::1:ff00:1)
Internet Control Message Protocol v6
Type: Neighbor Solicitation (135)
Code: 0
Checksum: 0x5aa6 [correct]
Reserved: 00000000
Target Address: 2000::1 (2000::1)
Is R1 trying to verify 2000::1 i not being used by any other ipv6 node?
Yes. The router is performing DAD on its global unicast IPv6 address.
Frame 7: 90 bytes on wire (720 bits), 90 bytes captured (720 bits)
Ethernet II, Src: c0:00:0c:98:00:00 (c0:00:0c:98:00:00), Dst: IPv6mcast_00:00:00:16 (33:33:00:00:00:16)
Internet Protocol Version 6, Src: fe80::c200:cff:fe98:0 (fe80::c200:cff:fe98:0), Dst: ff02::16 (ff02::16)
Internet Control Message Protocol v6
Type: Multicast Listener Report Message v2 (143)
Code: 0
Checksum: 0xa2d8 [correct]
Reserved: 0000
Number of Multicast Address Records: 1
Multicast Address Record Changed to exclude: ff02::1:ff98:0
Record Type: Changed to exclude (4)
Aux Data Len: 0
Number of Sources: 0
Multicast Address: ff02::1:ff98:0 (ff02::1:ff98:0)
What is the purpose of this packet?
This is a multicast join into solicited-node multicast group for the router's link-local IPv6 address. As this is MLDv2, it is source-and-group specific. The "Change to exclude" with an empty source list means "exclude no one". In other words, the router simply wants to receive a multicast traffic for this particular solicited-node multicast group (related to the router's link-local IPv6 address) from all sources.
Best regards,
Peter
01-12-2012 07:28 AM
Hi Sarah,
Frame 2: 78 bytes on wire (624 bits), 78 bytes captured (624 bits)
Ethernet II, Src: c0:00:0c:98:00:00 (c0:00:0c:98:00:00), Dst: IPv6mcast_ff:98:00:00 (33:33:ff:98:00:00)
Internet Protocol Version 6, Src: :: (::), Dst: ff02::1:ff98:0 (ff02::1:ff98:0)
Internet Control Message Protocol v6
Type: Neighbor Solicitation (135)
Code: 0
Checksum: 0xadf6 [correct]
Reserved: 00000000
Target Address: fe80::c200:cff:fe98:0 (fe80::c200:cff:fe98:0)
What is router trying to do? is it trying to verify the link local adress fe80::c200:cff:fe98:0 not being used by some other ipv6 node?
Yes. The router is performing Duplicate Address Detection (DAD) on its link-local address. While the link-local addresses are usually automatically assigned and derived from MAC addresses, they are nevertheless configurable and are subject to DAD just like any other IPv6 address.
Frame 6: 78 bytes on wire (624 bits), 78 bytes captured (624 bits)
Ethernet II, Src: c0:00:0c:98:00:00 (c0:00:0c:98:00:00), Dst: IPv6mcast_ff:00:00:01 (33:33:ff:00:00:01)
Internet Protocol Version 6, Src: :: (::), Dst: ff02::1:ff00:1 (ff02::1:ff00:1)
Internet Control Message Protocol v6
Type: Neighbor Solicitation (135)
Code: 0
Checksum: 0x5aa6 [correct]
Reserved: 00000000
Target Address: 2000::1 (2000::1)
Is R1 trying to verify 2000::1 i not being used by any other ipv6 node?
Yes. The router is performing DAD on its global unicast IPv6 address.
Frame 7: 90 bytes on wire (720 bits), 90 bytes captured (720 bits)
Ethernet II, Src: c0:00:0c:98:00:00 (c0:00:0c:98:00:00), Dst: IPv6mcast_00:00:00:16 (33:33:00:00:00:16)
Internet Protocol Version 6, Src: fe80::c200:cff:fe98:0 (fe80::c200:cff:fe98:0), Dst: ff02::16 (ff02::16)
Internet Control Message Protocol v6
Type: Multicast Listener Report Message v2 (143)
Code: 0
Checksum: 0xa2d8 [correct]
Reserved: 0000
Number of Multicast Address Records: 1
Multicast Address Record Changed to exclude: ff02::1:ff98:0
Record Type: Changed to exclude (4)
Aux Data Len: 0
Number of Sources: 0
Multicast Address: ff02::1:ff98:0 (ff02::1:ff98:0)
What is the purpose of this packet?
This is a multicast join into solicited-node multicast group for the router's link-local IPv6 address. As this is MLDv2, it is source-and-group specific. The "Change to exclude" with an empty source list means "exclude no one". In other words, the router simply wants to receive a multicast traffic for this particular solicited-node multicast group (related to the router's link-local IPv6 address) from all sources.
Best regards,
Peter
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide