The document provides an overview of port aggregation or EtherChannel technology in Cisco switches, which allows linking of multiple physical ports together to form a single logical trunk link. It discusses the two protocols supported, PAgP and LACP, and how EtherChannel uses hashing algorithms on source and destination IP addresses to determine which physical link to use for a packet. Configuration examples are also given for setting up EtherChannel bundles using both protocols.

1. A.K. Gautam
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2. A.K. Gautam
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PORT AGGREGATION/ETHERCHANNEL
Spanning tree protocol only allows a single link between switch to switch because it prevents bridge loop.
Cisco Ether channel technology allows for the scaling of the link bandwidth by aggregating or bundling parallel links.
In Ether channel treats multiple line as a single link, logical link. The ether channel allows for two or eight links.
The Cisco catalyst family of switches supports two types of link aggregation.
PAgP (port aggregation protocol): - It is cisco proprietary protocol. It is default protocol, when we port channel
created.
LACP (link aggregation control protocol): - It is industy standard protocol. Its standard IEEE 802.3ad based protocol.
Etherchannel provide redundancy.
If one link fails traffic is automatically moved to another link.
Conditions:-
1. Both side same media type and speed.
2. Same duplex.
3. Same Vlan(If access)
4. Same trunking encapsulation and mode(if trunk)
5. Same native vlan.
Note: - Load is not balanced equally across links.
Etherchannel uses a hashing algorithm. Two inputs are used (Source IP address and Destination IP address)
How this work.
We will focus on the 2, 4, or 8 link because it is easier to understand for you.
A 2 link Etherchannel bundle require a 1 bit index using an XOR.
If the index is 0, link 0 is selected.
If the index is 1, link 1 is selected.
A 4 link Etherchannel bundle requires a 2 bit index using an XOR.
4 possible links: 00, 01, 10, 11
Let’s See
00 = link 0
01 = link 1
10 = link 2
11 = link 3
An 8 link etherchannel bundle requires a 3 bit index using an XOR.
8 possible links: 000, 001, 010, 011, 100, 101, 110, 111.
Same as:-
000 = link 0
001 = link 1
010 = link 2
011 = link 3
100 = link 4
101 = link 5
110 = link 6
111 = link 7
Note: - XOR (Exclusive OR), 0 value = false, 1 value = True. If boot bits have same value (both 0, both 1), the XOR will
result in a 0. Otherwise, if these value are different (one is a 0 and other is a 1), the result will be 1.

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Example: 2 Link
EtherChannel.
Packet sent from 172.16.1.1 to 10.10.10.16. The chosen hash uses Source IP (172.16.1.1) and Destination IP
(10.10.10.16) address.
172.16.1.1 => 00000001 (Source IP address)
10.10.10.16 => 00001000 (Destination IP address)
In our example we have 2 links in the EtherChannel (1 bit index):
 The XOR is performed only one rightmost(right side) bit 1 XOR 0
 1 XOR 0 = 1
 Link 1 is used
Note: - XOR of the two bits result in 0, then link 0 is used. If XOR of the two bits result in 1, then link 1 is used.
Example: 4 Link EtherChannel.
Link 0
Link 3
Packet sent from 172.16.1.1 to 10.10.10.46. The chosen hash uses Source IP (172.16.1.1) and Destination IP
(10.10.10.46) address.
172.16.1.1 => 00000001 (Source IP address)
10.10.10.46 => 00001110 (Destination IP address)
In our example we have 4 links in the EtherChannel (2 bit index):
The XOR is performed only 2 rightmost (right side) bit 01 XOR 00
Each bit is computed separately
01 XOR 10 = 11
1 XOR 0 = 1

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0 XOR 1 = 1
According to link
0 XOR 0 = 0 link = 0
0 XOR 1 = 1 link = 1
1 XOR 0 = 1 link = 2
1 XOR 1 = 0 link = 3
Link 0
Example: 4 Link EtherChannel
Link 7
Packet sent from 172.16.1.1 to 10.10.10.46. The chosen hash uses Source IP (172.16.1.1) and Destination IP
(10.10.10.46) address.
172.16.1.1 => 00000001 (Source IP address)
10.10.10.46 => 00001110 (Destination IP address)
If there are 8 links in the EtherChannel (3 bit index):
The XOR is performed only on the 3 rightmost bits 001 XOR 110
Each bit is computed separately
001 XOR 110 = 111
1 XOR 0 = 1
0 XOR 1 = 1
0 XOR 1 = 1
According to link
8 possible links: 000, 001, 010, 011, 100, 101, 110, 111.
Same as:-
000 = link 0
001 = link 1
010 = link 2
011 = link 3
100 = link 4
101 = link 5
110 = link 6
111 = link 7
See more Information:-
 http://www.cisco.com/en/US/tech/tk389/tk213/technologies_tech_note09186a0080094714.shtml

5. A.K. Gautam
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CONFIGURE ETHERCHANNEL LOAD BALANCING.
EthjerChannel
On On
PAgP Negotiated EtherChannel
Desirable EtherChannel Auto
LACP Negotiated EtherChannel
Active Passive
Load balancing configure on Global mode.
Switch(config)# port-channel load-balance method
Switch(config)# port-channel load-balance ?
dst-ip Dst IP Addr bits
dst-mac Dst Mac Addr bits
src-dst-ip Src XOR Dst IP Addr XOR
src-dst-mac Src XOR Dst Mac Addr XOR
src-ip Src IP Addr bits
src-mac Src Mac Addr bits
EtherChannel protocol
The Cisco Catalyst family of switches supports both:
Port Aggregation Protocol (PAgP) - Cisco proprietary (Default when port channel is created).
Link Aggregation Control Protocol (LACP) - Industry standard 802.3ad-based protocol (When a Cisco switch is
connected to a non-Cisco switch use LACP)
Note: - Must be same protocol on the both side.
switch(config)# interface range fa 0/1 - 4
switch(config-if-range)# channel-protocol ?
lacp Prepare interface for LACP protocol
pagp Prepare interface for PAgP protocol
switch(config-if-range)# channel-protocol pagp
Channel-group number: 1 – 64
(Does not need to be the same on both switches but it’s recommended that it usually is)
switch(config)# interface range fa 0/1 - 4
switch(config-if-range)# channel-protocol ?
lacp Prepare interface for LACP protocol
pagp Prepare interface for PAgP protocol

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switch(config-if-range)# channel-group number mode {active | on | {auto [non-
silent]} | {desirable [non-silent]} | passive}
if No PAgP or LACP negotiation used
switch(config)# interface range fa 0/1 – 4
switch(config-if-range)# channel-protocol pagp
switch(config-if-range)# channel-group 1 mode on
active Enable LACP unconditionally
auto Enable PAgP only if a PAgP device is detected
desirable Enable PAgP unconditionally
on Enable Etherchannel only
passive Enable LACP only if a LACP device is detected
Note: - Both ends must be on
PAgP (Port Aggregation Protocol)
PAgP modes: -
1: -Desirable
2: -Auto
1:- in this mode switch sends a request to neighbor switch for either channel negotiation.
2:- in this mode a switch read for negotiation but it does not send a request to neighbor switch for either channel
negotiation.
Switch1(config)# interface range fa 0/1 – 4
Switch1(config-if-range)#switchport mode trunk
Switch1(config-if-range)# switchport trunk encapsulation dot1q
Switch1(config-if-range)# channel-protocol pagp
Switch1(config-if-range)# channel-group 1 mode desirable
Switch2(config)# interface range fa 0/1 – 4
Switch2(config-if-range)#switchport mode trunk
Switch2(config-if-range)#switchport trunk encapsulation dot1q
Switch2(config-if-range)# channel-protocol pagp
Switch2(config-if-range)# channel-group 1 mode auto
Note: - Load balancing does not have to match.
switch1(config)# port-channel load-balance dst-ip
switch2(config)# port-channel load-balance src-dst-ip
Verifying: -
Switch#show etherchannel protocol
Switch#show etherchannel load-balance
Switch#show ehterchannel summary
Switch#show etherchannel port

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LACP (Link Aggregation control Protocol)
LACP Modes: -
1: -Active:
2: -Passive:
1: - An interface in the active mode can negotiation an EtherChannel with another interface that is in the active or
passive mode.
2: - An interface in the passive mode cans negotiation an EtherChannel with another interface that is in the active
mode.
Note: - An interface in the passive mode cannot negotiation an EtherChannel with another interface that is also in
the passive mode because neither interface starts LACP negotiation.
Switch1(config)# interface range fa 0/1 – 4
Switch1(config-if-range)#switchport mode trunk
Switch1(config-if-range)# switchport trunk encapsulation dot1q
Switch1(config-if-range)# channel-protocol lacp
Switch1(config-if-range)# channel-group 1 mode active
Switch2(config)# interface range fa 0/1 – 4
Switch2(config-if-range)#switchport mode trunk
Switch2(config-if-range)#switchport trunk encapsulation dot1q
Switch2(config-if-range)# channel-protocol lacp
Switch2(config-if-range)# channel-group 1 mode passive
Port Priority
LACP uses the port priority to decide which port should be put in standby mode.
Ports with lower priority are active, and rest ports are standby (Default
32678).
For Example we use 4 links.
Switch1(config)# interface range fa 0/1 – 2
Switch1(config-if-range)#switchport mode trunk
Switch1(config-if-range)# switchport trunk encapsulation dot1q
Switch1(config-if-range)# channel-protocol lacp
Switch1(config-if-range)# channel-group 1 mode active
Switch1(config-if-range)#lacp port-priority 99
Switch1(config)# interface range fa 0/3 – 4
Switch1(config-if-range)#switchport mode trunk
Switch1(config-if-range)#switchport trunk encapsulation dot1q
Switch1(config-if-range)# channel-protocol lacp
Switch1(config-if-range)# channel-group 1 mode passive
Note: - Load balancing does not have to match.
switch1(config)# port-channel load-balance dst-ip
switch2(config)# port-channel load-balance src-dst-ip
Verifying: -
Switch#show etherchannel protocol

8. A.K. Gautam
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Switch#show etherchannel load-balance
Switch#show ehterchannel summary
Switch#show etherchannel port
Thanks giving me your precious time.
A.K. Gautam