Configuring Port Aggregation

Summary: Networking › Switching › Edge › Synapse

Overview of Port Aggregation

Port aggregation provides fault-tolerant high-speed links between switches, routers, and servers. You can use it to increase the bandwidth between the wiring closets and the data center, and you can deploy it anywhere in the network where bottlenecks are likely to occur. Port aggregation provides automatic recovery for the loss of a link by redistributing the load across the remaining links. If a link fails, port aggregation redirects traffic from the failed link to the remaining links in the channel without intervention. Port aggregation consists of individual Fast Ethernet or Gigabit Ethernet links bundled into a single logical link called channel, as shown in Figure below.

Typical Port Aggregation application

Each Channel can consist of up to eight compatibly configured Ethernet ports. All ports in each Channel must be configured as Layer 2 ports. The number of Channels is limited to 12. You can configure an Channel in one of these modes: Manual(Static), Active(LACP), or Passive(LACP).

Overview of LACP

LACP (Link Aggregation Control Protocol) based on the IEEE802.3ad standard is a dynamic link aggregation protocol. If a port enables the LACP, the port will send LACPDU message to announce its system priority, system MAC, port priority, port number and operation key, etc. After the connected device receives the LACP message from the peer end, it compares the system priorities of the two ends according to the system ID in the message. On the side with the higher system ID priority, the ports in the aggregation group are set to be in the aggregation state according to the order of port ID priority from high to low, and the updated LACP message is sent out. It will also set the corresponding port to the aggregation state, so that the two sides can reach the same agreement when the port exits or joins the aggregation group. After the LACP member interface link is bound, periodic LACP packet exchange will be carried out. When no LACP packet is received for a period of time, it is considered that the packet reception timed out, the member interface link is unbound, and the port is in a state of non-forwarding again. There are two modes of timeout here: long timeout mode and short timeout mode. In the long timeout mode, the port sends a packet every 30 seconds. If it does not receive a packet from the peer for 90 seconds, it will be in a packet receiving timeout.；In the short timeout mode, the port sends a packet every 1 second. If it does not receive a packet from the peer for 3 seconds, it is in the packet receiving timeout.

Figure Typical LACP application

As shown Figure, switch A and switch B are connected together through 3 ports. We set the system priority of switch A to 61440, and set the system priority of switch B to 4096. Enable LACP link aggregation on the three directly connected ports of switches A and B. After receiving the LACP message from the peer, switch B finds that its system ID has a higher priority (switch B has a higher system priority than switch A), so it follows the order of port ID priority (in the case of the same port priority) , in the order of port numbers from small to large) set ports 4, 5, and 6 to be in the aggregation state. After switch A receives the updated LACP packet from switch B, it finds that the system ID of the peer end has a higher priority, and set the ports 1, 2, and 3 to the aggregation state.

Configuring

• Configuring Layer 2 Channels

SWITCH(config-if)#channel-group ID mode manual

SWITCH(config-if)#channel-group ID mode {active | passive}

SWITCH(config-if)#no channel-group

Assign the port to a channel group, and specify the mode. For ID, the range is 1 to 12.

Note

✦ When the first port is added to the aggregation port, a PO port is actively created, and the default attribute of the PO port is the first port attribute. ✦ For Layer 2 Channels: Ports with different native VLANs cannot form an EtherChannel.

• Configuring LACP System Priority

SWITCH(config)#lacp system-priority SYSTEM-PRIORITY

SWITCH(config)#no lacp system-priority

The system priority range is 1 to 65535, the default value is 32768. All dynamic link groups of a device can only have one LACP system priority. Modifying this value will affect all aggregation groups on the switch.

SWITCH(config-if)#lacp port-priority PORT-PRIORITY

SWITCH(config-if)#no lacp port-priority

The interface priority range is 1 to 65535, the default value is 32768.

SWITCH(config-if)#lacp timeout {long | short}

SWITCH(config-if)#no lacp timeout

In long mode, the interval for sending LACP protocol packets is 30S, and the timeout is 90S. In short mode, the interval for sending LACP protocol packets is 1S, and the timeout is 3S. Default is in long mode.

SWITCH(config)#port-channel load-balance {dst-ip | dst-mac | dst-port | src-dst-ip | src-dst-mac | src-dst-port | src-ip | src-mac | src-port}

SWITCH(config)#no port-channel load-balance

Configure an Channel load-balancing method. The default is src-mac. Select one of these load-distribution methods: • dst-ip: Load distribution is based on the destination IP address. dst-mac: Load distribution is based on the destination MAC address of the incoming packet. Dist-port: Load distribution is based on the destination L4-port of the incoming packet src-dst-ip: Load distribution is based on the source-and-destination IP address. src-dst-mac: Load distribution is based on the source-and-destination MAC address. src-dst-port: Load distribution is based on the source-and-destination L4-port of the incoming packet. src-ip: Load distribution is based on the source IP address. src-mac: Load distribution is based on the source-MAC address of the incoming packet.

Examples

Example 1: This example shows how to assign the ports to a channel, and set load-balance method.

• Assign the gigabitEthernet0/5, gigabitEthernet0/6 to PO 1, set load-balance to src-ip：

SWITCH(config)#interface gigabitEthernet0/5

SWITCH(config-if)#channel-group 1 mode manual

SWITCH(config-if)#exit

SWITCH(config)#interface gigabitEthernet0/6

SWITCH(config-if)#channel-group 1 mode manual

SWITCH(config-if)#exit

SWITCH(config)#port-channel load-balance src-ip

Display information

• Display Channels Configuration and Status

SWITCH#show port-channel

Load balance: Source and Destination Mac address Interface po3 Type: static Member: gigabitEthernet0/18 link down Disable Interface po8 Type: LACP Member: gigabitEthernet0/19 link up Enable gigabitEthernet0/17 link up Enable

SWITCH#show port-channel 8

Interface po8 Type: LACP Member: gigabitEthernet0/19 link up Enable gigabitEthernet0/17 link up Enable

SWITCH#show port-channel load-balance

Source and Destination Mac address

• Display LACP Summary

SWITCH#show lacp summary

% Aggregator po8 1008 % Aggregator Type: Layer2 % Admin Key: 0008 – Oper Key 0008 % Link: gigabitEthernet0/17 (17) sync: 1 status: Bundled % Link: gigabitEthernet0/19 (19) sync: 1 status: Bundled

SWITCH#show lacp detail

% Aggregator po8 1008 % Aggregator Type: Layer2 % Mac address: 74:b9:eb:ee:25:46 % Admin Key: 0008 – Oper Key 0008 % Actor LAG ID- 0x8000,74-b9-eb-ee-25-46,0×0008 % Receive link count: 2 – Transmit link count: 2 % Individual: 0 – Ready: 1 % Partner LAG ID- 0x8000,00-01-a0-00-10-10,0×0032 % Link: gigabitEthernet0/17 (17) sync: 1 status: Bundled % Link: gigabitEthernet0/19 (19) sync: 1 status: Bundled

SWITCH#show lacp 8

% Aggregator po8 1008 Admin Key: 0008 – Oper Key 0008 % Partner LAG ID: 0x8000,00-01-a0-00-10-10,0×0032 % Partner Oper Key 0050

SWITCH#show lacp sys-id

% System 8000,74-b9-eb-ee-25-46

SWITCH#show lacp port gigabitEthernet0/19

% LACP link info: gigabitEthernet0/19 – 19 % LAG ID: 0x8000,74-b9-eb-ee-25-46,0×0008 % Partner oper LAG ID: 0x8000,00-01-a0-00-10-10,0×0032 % Actor Port priority: 0x8000 (32768) % Admin key: 0x0008 (8) Oper key: 0x0008 (8) % Physical admin key:(1) % Receive machine state : Current % Periodic Transmission machine state : Slow periodic % Mux machine state : Collecting/Distributing % Oper state: ACT:1 TIM:0 AGG:1 SYN:1 COL:1 DIS:1 DEF:0 EXP:0 % Partner oper state: ACT:1 TIM:0 AGG:1 SYN:1 COL:1 DIS:1 DEF:0 EXP:0 % Partner link info: admin port 0 % Partner oper port: 20 % Partner admin LAG ID: 0x0000-00:00:00:00:0000 % Admin state: ACT:1 TIM:0 AGG:1 SYN:0 COL:0 DIS:0 DEF:1 EXP:0 % Partner admin state: ACT:0 TIM:0 AGG:1 SYN:0 COL:0 DIS:0 DEF:1 EXP:0 % Partner system priority – admin:0x0000 – oper:0x8000 % Partner port priority – admin:0x0000 – oper:0x8000 % Aggregator ID: 1008

SWITCH#show int po8

Interface po8 Hardware is AGG Current HW addr: 74b9.ebee.2546 Logical:(not set)

Port Mode is access

interface configure: medium-fiber mtu 1526 speed-auto duplex-auto flowcontrol-off autonego-off interface status: link-up bandwidth-2g Aggregate Members:(LACP) gigabitEthernet0/19 link up Enable gigabitEthernet0/17 link up Enable input packets: Good Octets Rx : 18986 Good Packets Rx : 104 Broadcast Packets Rx : 0 Multicast Packets Rx : 104 ouput packets: Good Octets Tx : 38529 Good Packets Tx : 359 Broadcast Packet Tx : 4 Multicast Packet Tx : 355 un-normal packets: Drop Events : 0 Undersized Pkts Recvd : 0 Oversized Pkts Recvd : 0 Bad CRC : 0