Finisar Surveyor 用户手册
10-71
Expert Features
Network Layer
10
ICMP Fragmentation Needed [D/F set]
Counter
ICMP Fragmentation Needed [D/F set] 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
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 Fragmentation Needed [D/F] set events are automatically logged as expert
symptoms. The
symptoms. The
Symptom Summary
field provides information about the IP
addresses involved. For example:
MTU of next Hop=2 to reach [206.250.228.69]. Cannot be
reached by [206.250.228.11] as D/F Set.
SA=[206.250.228.11] DA=[206.250.228.69]
Diagnostic Details
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Problem Description:
An ICMP Destination (Fragmentation needed, but, D/F set) Unreachable
message has been sent.
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. If the packet needs to be fragmented and the “don’t fragment” flag is set the
2. If the packet needs to be fragmented and the “don’t fragment” flag is set the
host/router will send this message.
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 D/F is meant to be set (no action required).
2. Check the netmask configuration of the source.
3. Ignore this message if the D/F is meant to be set (no action required).