Cisco Catalyst 2000 Configuration Handbook page 237

216 Cisco LAN Switching Configuration Handbook
(Optional) Use Layer 3 traceroute to discover routers along a path:
2.
(exec) traceroute [protocol] [host]
The traceroute command sends successive probe packets to host (either a network
address or a hostname).
For IP, the first set of packets (default 3) is sent with a TTL of one. The first router
along the path decrements the TTL, detects that it is zero, and returns ICMP TTL-
exceeded error packets. Successive sets of packets are then sent out, each one with a
TTL value incremented by one. In this fashion, each router along the path responds
with an error, allowing the local router to detect successive hops.
The following fields are output as a result of traceroute probes:
Set DF bit in IP header (default no): If set, the packet is not fragmented
■
for a path with a smaller MTU; you can use this to detect the smallest
MTU in the path.
Validate reply data (default no): The data sent in the echo request packet
■
is compared to the data echoed in the reply packet.
Data pattern (default 0xABCD): The data pattern is a 16-bit field that is
■
repeated throughout the data portion of the packet; this can prove use-
ful for testing data integrity with CSU/DSUs and cabling.
Loose, strict, record, timestamp, verbose (default none): loose (loose
■
source route with hop addresses), strict (strict source route with hop
addresses), record (record the route with a specified number of hops),
timestamp (record time stamps at each router hop), and verbose (toggle
verbose reporting). The record option can be useful to see a record of
the router addresses traversed over the round-trip path.
■ Sweep range of sizes (default no): Sends echo requests with a variety of pack-
et sizes:
Sweep min size (default 36)
■
■ Sweep max size (default 18024)
Sweep interval (default 1)
■
■ Probe sequence number: The current hop count.
Hostname of the current router.
■
IP address of the current router.
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■ Round-trip times (in milliseconds) of each of the probes in the set.
*: The probe timed out.
■
U: Port unreachable message was received.
■
■ H: Host unreachable message was received.