Etherchannel - Cisco Catalyst 2000 Configuration Handbook

62 Cisco LAN Switching Configuration Handbook
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Display stored TopN report:
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show top counters interface report [report_num]
You can view a specific TopN report numbered report-num. To see a list of all the
stored TopN reports, omit the report number. Reports are stored in switch memory
and remain there until the switch is rebooted or loses power. To clear TopN reports
from memory, use the clear top [all | report-num] command.

4-4: EtherChannel

You can aggregate several individual switch ports into a single logical port or
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EtherChannel.
Fast Ethernet ports, when bundled together, form a Fast EtherChannel (FEC).
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Gigabit ports form a Gigabit EtherChannel (GEC).
■ You can manually configure EtherChannels or aggregate them through the use of
dynamic protocols. PAgP is a Cisco proprietary protocol, whereas Link Aggregation
Control Protocol (LACP) is a standards-based protocol defined in IEEE 802.3ad
(also known as IEEE 802.3 Clause 43, "Link Aggregation").
■ Frames are distributed onto the individual ports that make up an EtherChannel by
using a hashing algorithm. The algorithm can use source, destination, or a combina-
tion of source and destination IP addresses, source and destination MAC addresses,
or TCP/UDP port numbers, depending on the hardware platform and configuration.
■ Frame distribution is deterministic; that is, the same combination of addresses or
port numbers always points to the same port within the EtherChannel.
The frame distribution hashing algorithm performs an exclusive-OR (XOR) opera-
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tion on one or more low-order bits of the addresses or TCP/UDP port numbers to
select on which link a frame will be forwarded. For a two-port bundle, the last bit is
used; a four-port bundle uses the last two bits; and an eight-port bundle uses the last
three bits. (With XOR, if two bits are identical, a 0 bit results; if two bits are differ-
ent, a 1 bit results.)
Broadcast: Number of input/output broadcast packets.
Bytes: Number of input/output bytes.
Errors: Number of input errors.
Multicast: Number of input/output multicast packets.
Overflow: Number of buffer overflows.
Packets: Number of input/output packets.
Utilization: When calculating the port utilization, TopN reports bundle the Tx
and Rx lines into the same counter and also look at the full-duplex bandwidth
when calculating the percentage of utilization. For example, a Gigabit Ethernet
port would be 2000-Mbps full duplex.