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13.1 and 2 - Coggle Diagram
13.1 and 2
13.1 - ICMPv4 and ICMPv6 Messages
Internet Control Message Protocol (ICMP) provides feedback about issues related to the
processing of IP packets under certain conditions
ICMPv4 is the messaging protocol for IPv4. ICMPv6 is the messaging protocol for IPv6 and
includes additional functionality
The ICMP messages common to both ICMPv4 and ICMPv6 include:
host reachability
ICMP Echo Message can be used to test the reachability of a host on an IP network
destination or service unreachable
An ICMP destination unreachable message can be used to notify the source that a destination or service is unreachable
The ICMP message will include a code indicating why the packet could be delivered
A few destination unreachable codes for ICMPv4 are:
0 - Net unreachable
1 - Host unreachable
2 - Protocol unreachable
A few destination codes for ICMPv6 are:
0 - No route to destination
1 - Communication with the destination is administratively prohibited
2 - Beyond scope of the source address
3 - Address unreachable
4 - Port unreachable
time exceeded
When the Time to Live (TTL) field in a packet is decremented to 0 an ICMPv4 Time Exceeded message will be sent to the source host
ICMPv6 also sends a Time Exceeded message. Instead of the IPv4 TTL field, ICMPv6 uses the IPv6 Hop Limit to determine if the packet has expired
ICMPv6 Messages
ICMPv6 has new features and improved functionality not found in ICMPv4 including four new protocols as part of the Neighbor Protocol
Messaging between an IPv6 router and an IPv6 device including dynamic address allocation are:
Router Solicitation (RS) message
Router Advertisement (RA) message
Messaging between IPv6 devices including duplicate address detection and address resolution are:
Neighbor Solicitation (NS) message
Neighbor Advertisement (NA) message
RA messages are sent by IPv6-enabled routers every 200 seconds to provide addressing information to IPv6-enabled hosts
RA message can include addressing information for the host such as the prefix length, DNS address and domain name
A host using Stateless Address Autoconfiguration (SLAAC) will set its default gateway to the link-local address of the router of the router that sent the RA
An IPv6-enabled router will also send out an RA message in response to an RS message
A device assigned a global IPv6 unicast or link-local unicast address, may perform duplicate address detection (DAD) to ensure that the IPv6 address is unique
To check the uniqueness of an address the device will send an NS message with its own IPv6 address as the targeted IPv6 address
If another device on the network has this address it will respond with an NA message notifying to the sending device that the address is in use
To determine the MAC address for the destination the device will send an NS message to the solicited node address
The message will include the known IPv6 address. The device that has the targeted IPv6 address will respond with an NA message containing its Ethernet MAC address
13.2 - Ping and and Traceroute Tests
Ping - Test Connectivity
The 'ping' command is an IPv4 and IPv6 testing utility that uses ICMP echo request and echo reply messages to test connectivity between hosts and provides a summary that includes the success rate and average round-trip time to the destination
If a reply is not received within the timeout, ping provides a message indicating that a response was not received
It is common for the first ping to timeout if the address resolution needs to be performed before sending the ICMP Echo Resquest
Ping the Loopback
Ping can be used to test the internal configuration of the IPv4 or IPv6 on the local host. To do this, 'ping' the local loopback address of 127.0.0.1 for IPv4 and ::1 for IPv6
A response from 127.0.0.1 for IPv4 or ::1 IPv6 indicates that IP is properly installed on the host
An error message indicates that TCP/IP is not operational on the host
Ping the Default Gateway
The 'ping' command can be used to test the agility of a host to communicate on the local network
The default gateway address is most often used because the router is normally always operational
A successful 'ping' to the default gateway indicates that the host and the router interface serving as the default gateway are both operational on the local network
If the default gateway address does not respond, a 'ping' can be sent to the IP address of another host on the local network that is known to be operational
Ping a Remote Host
Ping can be used to test the ability of a local host to communicate across an internetwork