Finisar Surveyor, User Manual

Page: 279 / 454

10-75
Expert Features
Network Layer
10
ICMP Host Unreachable for TOS
Counter
ICMP Host Unreachable for TOS events are counted in the ICMP All Errors and the
ICMP Destination Unreachable counters. A count of all destination unreachable
ICMP symptoms and a count of all ICMP errors displays in the
Overview
counters
of Expert View. A threshold can be set in Expert Alarms for all destination
unreachable ICMP errors or for all ICMP errors.
Expert Symptom
ICMP Host Unreachable for TOS events are automatically logged as expert
symptoms. The
Symptom Summary
field provides information about the IP
addresses involved. For example:
TOS=22 service on [206.250.228.69] unavailable for
[206.250.228.11]. SA=[206.250.228.11] DA=[206.250.228.69]
Diagnostic Details
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Problem Description:
An ICMP Destination Host is Unreachable for TOS message has been sent.
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Probable Cause(s):
1. If a router has a routing table problem, it may send this message.
2. A host may send this message if a destination host is unreachable for the type
of service requested.
3. The source may have an incorrectly configured subnet mask.
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Recommended Action(s):
1. Check the routing tables of the router that this message was generated from.
2. Check the netmask configuration of the source.
3. Ignore this message if the host is truly unreachable for TOS (no action required).