What is an example of ICMP?
ICMP (Internet Control Message Protocol) is a network protocol used for diagnostics and network management. A good example is the “ping” utility which uses an ICMP request and ICMP reply message. When a certain host of port is unreachable, ICMP might send an error message to the source.
What are ICMP codes?
Internet Control Message Protocol (ICMP) Parameters
- Type 0 — Echo Reply.
- Type 1 — Unassigned.
- Type 2 — Unassigned.
- Type 3 — Destination Unreachable.
- Type 4 — Source Quench (Deprecated)
- Type 5 — Redirect.
- Type 6 — Alternate Host Address (Deprecated)
- Type 7 — Unassigned.
What does ICMP type 3 code 3 mean?
port unreachable error message
… port unreachable error message [Type 3, Code 3] is generated when a destination host cannot deliver a reply packet because the intended port is not active, for example, when a source computer A sends UDP request to port 53 of a target computer B that is not a DNS server.
What does ICMP type 3 code 13 mean?
An ICMP type 3, code 13 response means that the machine is down.
What are the most commonly employed ICMP message types?
Commonly used ICMP types are echo request and echo reply (used for ping) and time to live exceeded in transit (used for traceroute).
Does ASA inspect ICMP by default?
ICMP inspection is not enabled by default. Without being enabled, ICMP traffic is automatically not permitted through the ASA at all without additional security policy configuration.
What are the two categories of ICMP messages give two examples of each?
Following are the types of query messages :
- Echo-Request and Reply Message – It is used by the network managers to check the operations of the IP protocol and host’s reachability.
- Timestamp Request and Reply Message –
- Address Mask Request and Reply Message –
- Router Solicitation and Advertisement Message –
What ICMP types should I allow?
The only essential ICMP traffic you need to allow in and out of your firewall is Type 3 and Type 4. Everything else is either optional or should be blocked. Notes: To send ping requests, allow type 8 OUT and type 0 IN.