Priscilla Oppenheimer wrote:
>
> H means host unreachable. Jumping to the conclusion that there's a routing
> problem isn't logical (though I know that what's the Tech Note document
> says.) The host could be turned off. A host unreachable happens when the
> last-hop router tries to ARP for the device and doesn't get a response.
>
This isn't what I've seen and captured with a protocol analyzer, nor
viewed via debug. If any router is missing an ARP entry (or any other
type of next-hop data link address), it will silently drop the packet.
The output of "debug ip packet" will report "encapsulation failed".
OTOH, if any router in the chain lacks a route to the destination, that
router will generate an ICMP _host_ unreachable, not network unreachable.
I agree this is not intuitive, but here's the screen output from a
WinThing attempting to ping a bogus address, and the debug output from
its default gateway:
C:\WINDOWS>ping 10.0.0.1
Pinging 10.0.0.1 with 32 bytes of data:
Reply from 192.1.63.196: Destination host unreachable.
Reply from 192.1.63.196: Destination host unreachable.
Reply from 192.1.63.196: Destination host unreachable.
Reply from 192.1.63.196: Destination host unreachable.
Ping statistics for 10.0.0.1:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum = 0ms, Average = 0ms
--------------------------------------------------------------------------------------
06:47:58: ICMP: dst (10.0.0.1) host unreachable sent to 192.1.63.198
06:47:59: ICMP: dst (10.0.0.1) host unreachable sent to 192.1.63.198
06:48:00: ICMP: dst (10.0.0.1) host unreachable sent to 192.1.63.198
06:48:01: ICMP: dst (10.0.0.1) host unreachable sent to 192.1.63.198
Marty Adkins Email: [EMAIL PROTECTED]
Mentor Technologies Phone: 410-280-8840 x3006
275 West Street, Plaza 70 WWW: http://www.mentortech.com
Annapolis, MD 21401 Cisco CCIE #1289
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