Lab: ICMPv6 and ICMPv6 Neighbor Discovery CIS 116 IPv6 Fundamentals Enter your answers to the questions in this lab using Canvas Quiz DHCPv6 Lab. Part 1: Setup Step 1. Basics a. Log into NetLab: ccnp.bayict.cabrillo.edu b. Schedule IPv6 Pod 1: no configs loaded (clean) c. Configure each router with the following commands: Router> enable Router# conf t Router(config)# hostname <R1, R2 or R2> R1(config)# no ip domain-lookup R1(config)# line con 0 R1(config-line)# logging synchronous R1(config-line)# exec-timeout 0 0 Note: If using the interface configurations from a previous lab, make sure the router has not been configured as an IPv6 router: Router(config)# no ipv6 unicast-routing Step 2. Manual configuration of global unicast and link-local addresses Note: R2 and R3 are not used in this lab, but the configurations are provided for your enjoyment. J R1 conf t R1(config)# interface g 0/0 R1(config-if)# ipv6 address 2001:db8:cab:828::1/64 R1(config-if)# ipv6 address fe80::828:1 link-local R1(config-if)# no shutdown R1(config-if)# exit
R1(config)# interface g 0/1 R1(config-if)# ipv6 address 2001:db8:cab:1000::1/64 R1(config-if)# ipv6 address fe80::1 link-local R1(config-if)# no shutdown R1(config-if)# end R2 conf t R2(config)# interface g 0/1 R2(config-if)# ipv6 address 2001:db8:cab:1000::2/64 R2(config-if)# ipv6 address fe80::2 link-local R2(config-if)# no shutdown R2(config-if)# exit R2(config)# interface g 0/0 R2(config-if)# ipv6 address 2001:db8:cab:2000::2/64 R2(config-if)# ipv6 address fe80::2 link-local R2(config-if)# no shutdown R2(config-if)# end R3 R3# conf t R3(config)# interface g 0/1 R3(config-if)# ipv6 address 2001:db8:cab:2000::1/64 R3(config-if)# ipv6 address fe80::3 link-local R3(config-if)# no shutdown R3(config-if)# exit R3(config)# interface g 0/0 R3(config-if)# ipv6 address 2001:db8:cab:828::1/64 R3(config-if)# ipv6 address fe80::829:1 link-local R3(config-if)# no shutdown R3(config-if)# end Verify show ipv6 interface brief GigabitEthernet0/0 [up/up] FE80::828:1 2001:DB8:CAB:828::1 GigabitEthernet0/1 [up/up] FE80::1 2001:DB8:CAB:1000::1 show ipv6 interface brief GigabitEthernet0/0 [up/up] FE80::2 2001:DB8:CAB:2000::2 GigabitEthernet0/1 [up/up] FE80::2 2001:DB8:CAB:1000::2 R3# show ipv6 interface brief GigabitEthernet0/0 [up/up] FE80::829:1
2001:DB8:CAB:828::1 GigabitEthernet0/1 [up/up] FE80::3 2001:DB8:CAB:2000::1 R3# Step 3. Enabling the router as an IPv6 router Configure all three routers as IPv6 routers: R1(config)# ipv6 unicast-routing R2(config)# ipv6 unicast-routing R3(config)# ipv6 unicast-routing Step 4. Enabling EIGRP for IPv6 Enable all three routers for EIGRP for IPv6 R1(config)# ipv6 router eigrp 1 R1(config-router)# eigrp router-id 1.1.1.1 R1(config-router)# exit R1(config)# interface g 0/0 R1(config-if)# ipv6 eigrp 1 R1(config-if)# exit R1(config)# interface g 0/1 R1(config-if)# ipv6 eigrp 1 R1(config-if)# end R2(config)# ipv6 router eigrp 1 R2(config-router)# eigrp router-id 2.2.2.2 R2(config-router)# exit R2(config)# interface g 0/0 R2(config-if)# ipv6 eigrp 1 R2(config-if)# exit R2(config)# interface g 0/1 R2(config-if)# ipv6 eigrp 1 R2(config-if)# end R3(config)# ipv6 router eigrp 1 R3(config-router)# eigrp router-id 3.3.3.3 R3(config-router)# exit R3(config)# interface g 0/0 R3(config-if)# ipv6 eigrp 1 R3(config-if)# exit R3(config)# interface g 0/1 R3(config-if)# ipv6 eigrp 1 R3(config-if)# end R3#
Part 2: ICMPv6 Error Message Packet Too Big In this part you will examine what happens when a packet is received larger than the forwarding egress interface. Step 1. Modify the MTU Modify the MTU between R2 and R3 so it is less than the MTU of R1 s LAN. R2(config)# interface g 0/0 R2(config-if)# mtu 1350 R2(config-if)# R3(config)# interface g 0/1 R3(config-if)# mtu 1350 R3(config-if)# Step 2. Enable debug on R2 and send the extended pings from R1 Enable debug for ICMPv6 on R2 to monitor any ICMPv6 messages. debug ipv6 icmp ICMPv6 Packet debugging is on Using the extended ping command, from R1 s G0/0 interface ping the R3 s G0/0 interface. Use a datagram size of 1500 to ensure the packet size is greater than the MTU between R2 and R3. ping Protocol [ip]: ipv6 Target IPv6 address: 2001:db8:cab:829::1 Repeat count [5]: Datagram size [100]: 1500 Timeout in seconds [2]: Extended commands? [no]: yes Source address or interface: gigabitethernet0/0 UDP protocol? [no]: Verbose? [no]: Precedence [0]: DSCP [0]: Include hop by hop option? [no]: Include destination option? [no]: Sweep range of sizes? [no]: Type escape sequence to abort. Sending 5, 1500-byte ICMP Echos to 2001:DB8:CAB:829::1, timeout is 2 seconds: Packet sent with a source address of 2001:DB8:CAB:828::1 B!!!! Success rate is 80 percent (4/5), round-trip min/avg/max = 1/1/4 ms Notice the first ping failed. The B which refers to a Packet to Big message that was received. The rest of the pings were adjusted to the MTU sent in the ICMPv6 Packet to Big message and succeeded in being forwarded to their destination.
Examine the output from debug ip icmpv6 and notice the ICMPv6 Packet Too Big message sent to R1. Also, notice the MTU of the egress interface (1350) towards R3 is included in the Packet Too Big message back to R1. Disable debug with undebug all. *Nov 19 20:33:17.363: ICMPv6: Sent Too Big about 2001:DB8:CAB:829::1, MTU=1350, Src=2001:DB8:CAB:1000::2, Dst=2001:DB8:CAB:828::1 undebug all All possible debugging has been turned off Step 3. Reset the MTUs back to their default Reset the MTU between R2 and R3 to their defaults. R2(config)# interface g 0/0 R2(config-if)# no mtu R2(config-if)# R3(config)# interface g 0/1 R3(config-if)# no mtu R3(config-if)# Part 3: ICMPv6 Error Message Time Exceeded In this part you will examine what happens when a packet is received with a Hop Limit of 1. Step 1. Enable debug on R2 Enable debug for ICMPv6 on R2 to monitor any ICMPv6 messages. debug ipv6 icmp ICMPv6 Packet debugging is on Step 1. Send a traceroute from R1 to R3 s LAN Send a traceroute from R1 to R3 s G0/0 interface. traceroute 2001:db8:cab:829::1 Type escape sequence to abort. Tracing the route to 2001:DB8:CAB:829::1 1 2001:DB8:CAB:1000::2 0 msec 0 msec 0 msec 2 2001:DB8:CAB:2000::1 4 msec 0 msec 0 msec Examine the output from the debug ipv6 icmp command on R2. Notice the three ICMPv6 Time Exceeded messages sent to R1. This was the result of the first trace route with an initial Hop Limit of 1. *Nov 19 21:36:56.279: ICMPv6: Sent Time Exceeded, Src=2001:DB8:CAB:1000::2, Dst=2001:DB8:CAB:1000::1 *Nov 19 21:36:56.279: ICMPv6: Sent Time Exceeded, Src=2001:DB8:CAB:1000::2, Dst=2001:DB8:CAB:1000::1
*Nov 19 21:36:56.279: ICMPv6: Sent Time Exceeded, Src=2001:DB8:CAB:1000::2, Dst=2001:DB8:CAB:1000::1 Part 4: ICMPv6 Neighbor Discovery Router Solicitation and Router Advertisement In this part you will use Wireshark to do packet analysis on both Router Solicitation Message and Router Advertisement Message. Step 1. Using Wireshark In order for Wireshark to capture packets, the Ethernet interface must be enabled. Devices send a Router Solicitation message immediately after the Ethernet interface is enabled, which makes it difficult to capture with Wireshark. To solve this problem, we will do the Wireshark capture using another device. Using Windows PC 2, start Wireshark. Be sure the Local Area Connection is enabled: Capture > Interfaces or Once you have begun the capture, use the icmpv6 filter to restrict the number of packets displayed. Type icmpv6 in the autocomplete filter and clock Apply Next, start the Windows PC 1 VM. If you have it already started, restart the VM using Start > Shutdown > Restart. Step 2. Examining the ICMPv6 Router Solicitation Message Locate and examine the Router Solicitation Message. Ethernet II Destination: 33:33:00:00:00:02 (IPv6mcast)
Source: 00:50:56:af:97:68 Internet Protocol Version 6 0110... = Version: 6... 0000 0000............... = Traffic class: 0x00000000......... 0000 0000 0000 0000 0000 = Flowlabel: 0x00000000 Payload length: 16 Next header: ICMPv6 (58) Hop limit: 255 Source: fe80::d0f8:9ff6:4201:7086 Destination: ff02::2 Internet Control Message Protocol v6 Type: 133 (Router solicitation Code: 0 Checksum: 0x3277 [correct] ICMPv6 Option (Source link-layer address) Type: Source link-layer address (1) Length: 1 (8 bytes) Link-layer address: 00:50:56:af:97:68 Question 1: The destination IPv6 address is: Question 2: The destination MAC address of the RS message is an Ethernet: Question 3: The low-order 32 bits of the destination MAC address is copied from the: Step 3. Examining the ICMPv6 Router Advertisement Message Locate and examine the Router Advertisement Message. Ethernet II Destination: 33:33:00:00:00:01 (IPv6mcast) Source: 04:62:73:5e:f9:00 Internet Protocol Version 6 0110... = Version: 6... 1110 0000............... = Traffic class: 0x000000e0......... 0000 0000 0000 0000 0000 = Flowlabel: 0x00000000 Payload length: 64 Next header: ICMPv6 (58) Hop limit: 255 Source: fe80::828:1 Destination: ff02::1 Internet Control Message Protocol v6 Type: 134 (Router advertisement) Code: 0 Checksum: 0x79aa [correct] Cur hop limit: 64 Flags: 0x00 0...... = Managed address configuration: Not set
.0..... = Other configuration: Not set..0.... = Home Agent: Not set...0 0... = Prf (Default Router Preference): Medium (0)....0.. = Proxy: Not set.....0. = Reserved: 0 Router lifetime (s): 1800 Reachable time (ms): 0 Retrans timer (ms): 0 ICMPv6 Option (Source link-layer address : 04:62:73:5e:f9:00) Type: Source link-layer address (1) Length: 1 (8 bytes) Link-layer address: 04:62:73:5e:f9:00 (04:62:73:5e:f9:00) ICMPv6 Option (MTU : 1500) Type MTU (5) Length: 1 (8 bytes) Reserved MTU: 1500 ICMPv6 Option (Prefix information : 2001:db8:cab:828::/64) Type: Prefix information (3) Length: 4 (32 bytes) Prefix Length: 64 Flag: 0xc0 1...... = On-link flag(l): Set.1..... = Autonomous address-configuration flag(a): Set..0.... = Router address flag(r): Not set...0 0000 = Reserved: 0 Valid Lifetime: 2592000 Preferred Lifetime: 604800 Reserved Prefix: 2001:db8:cafe:1:: (2001:db8:cab:828::) Question 4: The destination IPv6 address is: Question 5: The destination MAC address of the RA message is an Ethernet: Question 6: The low-order 32 bits of the destination MAC address is copied from the: Question 7: The M Flag is set to: Question 8: The O Flag is set to: Question 9: The A Flag is set to: Question 10: The L Flag is set to: Part 5: ICMPv6 Neighbor Discovery Neighbor Solicitation and Neighbor Advertisement Step 1. Examining the ICMPv6 Neighbor Solicitation Message From router R1, ping WinPC 1 s global unicast address.
ping 2001:db8:cab:828:d0f8:9ff6:4201:7086 ICMPv6 Neighbor Solicitation and Neighbor Advertisement messages are used for Layer 3 to Layer 2 address resolution the same way as ARP Requests and ARP Replies in IPv4. The following NS and NA messages are a result of R1 pinging WinPC 1. Locate and examine the Neighbor Solicitation Message. Ethernet II Destination: 33:33:ff:01:70:86 (IPv6mcast) Source: 04:62:73:5e:f9:00 Internet Protocol Version 6 0110... = Version: 6... 0000 0000............... = Traffic class: 0x00000000......... 0000 0000 0000 0000 0000 = Flowlabel: 0x00000000 Payload length: 32 Next header: ICMPv6 (58) Hop limit: 255 Source: 2001:db8:cab:828::1 Destination: ff02::1:ff01:7086 Internet Control Message Protocol v6 Type: 135 (Neighbor solicitation) Code: 0 Checksum: 0x48ed [correct] Reserved: 0 (Should always be zero) Target: 2001:db8:cab:828:d0f8:9ff6:4201:7086 ICMPv6 Option (Source link-layer address) Type: Source link-layer address (1) Length: 8 (64 bytes) Link-layer address: 04:62:73:5e:f9:00 Question 11: The destination IPv6 address is: Question 12: The destination MAC address of the RA message is an Ethernet: Question 13: The low-order 32 bits of the destination MAC address is copied from the: Question 14: The target (IPv6 address) is: Step 2. Examining the ICMPv6 Neighbor Advertisement Message The following Neighbor Advertisement message is in response to the previous Neighbor Solicitation message. Locate and examine the Neighbor Solicitation Message. Ethernet II Destination: 04:62:73:5e:f9:00 Source: 00:50:56:af:97:68 Internet Protocol Version 6
0110... = Version: 6... 0000 0000............... = Traffic class: 0x00000000......... 0000 0000 0000 0000 0000 = Flowlabel: 0x00000000 Payload length: 32 Next header: ICMPv6 (58) Hop limit: 255 Source: 2001:db8:cab:828:d0f8:9ff6:4201:7086 Destination: 2001:db8:cab:828::1 Internet Control Message Protocol v6 Type: 136 (Neighbor advertisement) Code: 0 Checksum: 0xf621 [correct] Flags: 0x60000000 0........................= Router: Not set.1.......................= Solicited: Set..1......................= Override: Set...0 0000 0000 0000 0000 0000 0000 0000= Reserved: 0 Target: 2001:db8:cab:828:d0f8:9ff6:4201:7086 ICMPv6 Option (Target link-layer address) Type: Target link-layer address (2) Length: 1 (8 bytes) Link-layer address: 00:50:56:af:97:68 Question 15: The destination IPv6 address is: Question 16: The destination MAC address of the RA message is: Part 6: ICMPv6 Neighbor Discovery Neighbor Cache The Neighbor cache is used to maintain the mapping of IPv6-to-MAC addresses. Devices with an IPv6 address and an Ethernet interface will maintain an Neighbor cache. Step 1. Clear Neighbor Cache on R1 clear ipv6 neighbors show ipv6 neighbors Step 2. Debug IPv6 ND debug ipv6 nd ICMP Neighbor Discovery events debugging is on Step 3. From R1, Ping WinPC 1 ping 2001:db8:cab:828:d0f8:9ff6:4201:7086 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 2001:DB8:CAB:828:D0F8:9FF6:4201:7086, timeout is 2 seconds:
!!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/4 ms *Nov 20 02:30:35.482: ICMPv6-ND: (GigabitEthernet0/0,2001:DB8:CAB:828:D0F8:9FF6:4201:7086) Resolution request *Nov 20 02:30:35.482: ICMPv6-ND: (GigabitEthernet0/0,2001:DB8:CAB:828:D0F8:9FF6:4201:7086) DELETE -> INCMP *Nov 20 02:30:35.482: ICMPv6-ND: (GigabitEthernet0/0,2001:DB8:CAB:828:D0F8:9FF6:4201:7086) Sending NS *Nov 20 02:30:35.482: ICMPv6-ND: (GigabitEthernet0/0,2001:DB8:CAB:828:D0F8:9FF6:4201:7086) Queued data for resolution *Nov 20 02:30:35.486: ICMPv6-ND: (GigabitEthernet0/0,2001:DB8:CAB:828:D0F8:9FF6:4201:7086) Received NA from 2001:DB8:CAB:828:D0F8:9FF6:4201:7086 *Nov 20 02:30:35.486: ICMPv6-ND: (GigabitEthernet0/0,2001:DB8:CAB:828:D0F8:9FF6:4201:7086) LLA 0050.56af.9768 *Nov 20 02:30:35.486: ICMPv6-ND: (GigabitEthernet0/0,2001:DB8:CAB:828:D0F8:9FF6:4201:7086) INCMP -> REACH undebug all All possible debugging has been turned off Step 4. Display R1 s Neighbor Cache show ipv6 neighbors IPv6 Address 2001:DB8:CAB:828:D0F8:9FF6:4201:7086 Age Link-layer Addr State Interface 0 0050.56af.9768 REACH Gi0/0 <Wait 30 seconds> show ipv6 neighbors IPv6 Address 2001:DB8:CAB:828:D0F8:9FF6:4201:7086 Age Link-layer Addr State Interface 0 0050.56af.9768 STALE Gi0/0 Question 17: The ARP cache in IPv4 is equivalent to the in IPv6. Question 18: During address resolution, the neighbor cache is in Incomplete state right before sending a message. Question 19: During address resolution, the neighbor cache is in Incomplete state while waiting for a message. Question 20: If after 30 seconds or if no additional packets are received, the neighbor cache state will transition from the reachable state to the state.