Term
| Briefly describe the function of ICMP (high level). |
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Definition
a. Provides diagnostics and control info for the IP layer.
b. Delivers error and control messages for for layer 3 or higher to act upon.
b. Considered a L3 protocol.
d. Doesn't provide reliability for IP. |
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Term
| How does the ICMPv6 differ from ICMPv4? |
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Definition
ICMPv6 is used for several purposes beyond simple error reporting and signalling.
a. Neighbor Discovery
b. Router Discovery
c. Multicast address management
d. Handoff management in Mobile IPv6 |
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Term
| How is an ICMPv4 and ICMPv6 packet identified by IPv4 and IPv6 respectively? |
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Definition
a. The ICMPv4 header follows the IPv4 header and is identified by a value of 1 in the IPv4 Protocol field.
b. The ICMPv6 header follows the last IPv6 Extension Header and is identified by a value of 58 in the Next Header field. |
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Term
| Describe the ICMPv4 and ICMPv6 headers. |
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Definition
The header for each version has the same format:
a. 8-bit Type field.
b. 8-bit Code field.
c. 16-bit Checksum field.
d. Variable Data field - depends on Type and Code. |
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Term
| How is the Checksum calculated for ICMPv4 and ICMPv6? |
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Definition
a. ICMPv4 Checksum covers the entire ICMP message. It is changed at every hop.
b. ICMPv6 Checksum is a pseudo header which also covers the following IPv6 fields - SRC & DEST address, Length and Next Header. The ICMPv6 Checksum is end-to-end, i.e. it is not changed by any intermediate routers. |
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Term
| What are the 2 ICMP messaging categories? |
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Definition
a. Error messages - problems with delivering IP datagrams.
b. Query/Informational messages - info gathering and config. |
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Term
| List the common ICMPv4 message types. |
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Definition
a. Echo Reply (0) - reply to Ping
b. Destination Unreachable (3) - unreachable host/protocol
c. Redirect (5) - indicates alternate router should be used
d. Echo (8) - Ping request (data optional)
e. Time Exceeded (11) - resource exhausted e.g. IPv4 TTL
f. Parameter Problem (12) - malformed packet or header |
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Term
| Which of the common ICMPv4 message types may contain extension objects? |
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Definition
a. Destination Unreachable (3)
b. Redirect (5)
c. Echo (8)
d. Time Exceeded (11)
e. Parameter Problem (12) |
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Term
| List the common ICMPv4 Destination Unreachable (3) Codes. |
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Definition
0 - Network unreachable error - no route to destination
1 - Host unreachable error - known but unreachable host
3 - Port unreachable - unknown/unused transport port
4 - The datagram is too big - Fragmentation required but DF-bit set
13 - Communication Administratively Prohibited - comms filtered by policy |
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Term
| List the common ICMPv4 Redirect (5) Codes. |
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Definition
0 - Redirect datagram for the network - indicates alternate router
1 - Redirect datagram for the host - indicates alternate router (host)
2 - Redirect datagram for the type of Service and Network - indicates alternate router (TOS/net)
3 - Redirect datagram for the type of Service and Host - indicates alternate router (TOS/host) |
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Term
| Describe how ICMPv6 message Types are arranged. |
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Definition
a. 0-127 - Error messages
b. 128-255 - Informational messages |
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Term
| List some common ICMPv6 Error messages. |
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Definition
1 - Destination Unreachable
2 - Packet too Big
3 - Time exceeded
4 - Parameter Problem |
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Term
| List some common ICMPv6 Informational messages. |
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Definition
128-129 - Echo Request/Reply
133 - Router Solicitation
134 - Router Advertisement
135 - Neighbor Solicitation (ND)
136 - Neighbor Advertisement (ND)
137 - Redirect message |
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Term
| List the common ICMPv6 Destination Unreachable (1) codes. |
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Definition
0 - no route to destination
1 - administratively prohibited
2 - beyond scope of source address
3 - address unreachable
4 - port unreachable
5 - source address failed policy
6 - reject route to destination |
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Term
| If an ICMP message type only uses a single code, what code value will it use? |
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Definition
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Term
| Describe an ICMPv4 Unreachable packet. |
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Definition
a. 8-bit Type field
b. 8-bit Code field
c. 16-bit Checksum field
d. 8-bit unused
e. 8-bit Length (32-bit words)
f. 16-bit various - depends on Code
g. IPv4 header and some data
h. Extension (if applicable) |
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Term
| Describe an ICMPv6 Unreachable packet. |
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Definition
a. 8-bit Type field (5)
b. 8-bit Code field
c. 16-bit Checksum field
d. 8-bit Length (64-bit words)
e. 24-bit Unused
f. IPv4 header and some data
g. Extension (if applicable) |
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Term
| Describe an ICMPv4 Redirect packet. |
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Definition
a. 8-bit Type field (5)
b. 8-bit Code field
c. 16-bit Checksum field
d. 32-bit IP address of correct next hop
e. Offending packet up to max IP/ICMP packet size of 576 bytes |
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Term
| Describe an ICMPv6 Redirect packet. |
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Definition
a. 8-bit Type field (137)
b. 8-bit Code field
c. 16-bit Checksum field
d. 32-bit Reserved
e. 128-bit Target Address - the suggested next hop
f. 128-bit Destination Address - the destination in the offending packet
g. options (if any) |
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Term
| What type of packets are used for Traceroute? |
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Definition
a. UDP/IP datagrams are transmitted with ascending TTL values.
b. ICMP Time Exceeded datagrams are received by the device that decremented the TTL field to 0. |
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Term
| Which ICMP message type is used to highlight issues with an IP header? |
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Definition
| Parameter Problem - this is something of a catch all message |
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