NCAE Mapping Hub
Overview Scoreboard Data Roles Exercised Checklists Lessons Skill Drills Practice Terminal Progress
Router ICMP failure 1x weight measured

Router ICMP. ICMP 'destination unreachable' = routing is broken

ping says "Destination Host Unreachable" to host IP
Events
40
Pts per check
1.4
Pts missed
55.6
Teams hit
3/13

Authority mappings

Which work roles, knowledge units, and EWU courses this error pattern touches. Hover for context, click to drill in.

DCWF roles: CE-442 Network Technician CS-462 Control Systems Security Specialist IT-441 Network Operations Specialist IT-451 System Administrator
Knowledge Units: CD-BNW Basic Networking CD-NSA Network Security Administration CD-NTP Network Technology and Protocols CO-M4 Computer Networks
EWU courses: CSCD330 CSCD380 CSCD434 CSCD470

What the message means

Unlike a simple timeout, 'Destination Host Unreachable' means an intermediate router returned an explicit ICMP message saying it doesn't know how to reach your router. Your upstream routing is broken.

Why the service is down

Commands in order

  1. 1. 1. Does the router have a default gateway?
    /ip route print where dst-address=0.0.0.0/0
    Expect
    A single default route via your WAN gateway, active (A) flag
    Interpret and next
    Missing: `/ip route add dst-address=0.0.0.0/0 gateway=<wan-gw>`
  2. 2. 2. Is the WAN interface up?
    /interface print
    Expect
    WAN interface with R (running) flag
    Interpret and next
    Not running: enable + check cable/upstream.
  3. 3. 3. Can the router reach anywhere outside?
    /ping 8.8.8.8 count=3
    Expect
    3 successful pings
    Interpret and next
    All timeout = no internet. Your routing or gateway is broken.
  4. 4. 4. NAT masquerade present for LAN?
    /ip firewall nat print where action=masquerade
    Expect
    One srcnat rule with action=masquerade for your LAN
    Interpret and next
    Missing: `/ip firewall nat add chain=srcnat out-interface=<wan> action=masquerade`

Decision tree

Answer each question to route to the right fix.

Q: Can the router ping 8.8.8.8?
Yes: NAT masquerade is missing for outbound traffic.
No: Default gateway, WAN interface, or upstream. fix before anything else.

External references

Other patterns on this service