R1# sh run | sec ahmed batt
interface ahmed batt 0/0
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ipv6 address 25587::/64 eui
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Link-state tracking, also known as trunk failover, is a feature that binds the link state of multiple interfaces.
As shown in the our case study, server 1 and server 2 use switch A for primary links and switch B for secondary links to switches and other network devices. Server 3 and server 4 use switch B for primary links and switch A for secondary links. This configuration ensures that the traffic flow is balanced in the network. Ports connected to servers are referred to as downstream ports, and ports connected to distribution switches and network devices are referred to as upstream ports.
Configuring EtherChannels
Configuring Port Channel Logical Interfaces for Layer 3 EtherChannels
When configuring Layer 2 EtherChannels, you cannot put Layer 2 LAN ports into manually created port channel logical interfaces. When configuring Layer 3 EtherChannels, you must manually create the port channel logical interface as described in this section, and then put the Layer 3 LAN ports into the channel group. To create a port channel interface for a Layer 3 EtherChannel, perform this task:
! Creates the port channel interface.
Router(config)# interface port-channel group_number
! Assigns an IP address and subnet mask to the EtherChannel.
Router(config-if)# ip address ip_address mask
Router(config-if)# end
An EtherChannel bundles individual Ethernet links into a single logical link that provides the aggregate bandwidth of up to eight physical links. Cisco IOS supports a maximum of 128 EtherChannels. All LAN ports in each EtherChannel must be the same speed and must all be configured as either Layer 2 or Layer 3 LAN ports.
You can configure EtherChannels manually or you can use the Port Aggregation Control Protocol (PAgP) or the Link Aggregation Control Protocol (LACP) to form EtherChannels. The EtherChannel protocols allow ports with similar characteristics to form an EtherChannel through dynamic negotiation with connected network devices. PAgP is a Cisco-proprietary protocol and LACP is defined in IEEE 802.3ad.
Carrier Sense with Multiple Access with Collision Detection (CSMA/CD)
1. Carrier sense multiple access collision detect (CSMA/CD) describes the Ethernet access method.
2. In Ethernet, multiple access is the terminology for many stations attaching to the same cable and having the opportunity to transmit. No station has any priority over any other station. However, they do need to take turns per the access algorithm.
3. Carrier sense refer to if the Ethernet device wishing to communicate looks for energy on the media (an electrical carrier). If a carrier exists, the cable is in use and the device must wait to transmit. Many Ethernet devices maintain a counter of how often they need to wait before they can transmit. Some devices call the counter a deferral or back‐off counter. If the deferral counter exceeds a threshold value of 15 retries, the device attempting to transmit assumes that it will never get access to the cable to transmit the packet. In this situation, the source device discards the frame. This might happen if there are too many devices on the network, implying that there is not enough bandwidth available.
4. If the power level exceeds a certain threshold, that implies to the system that a collision occurred. When stations detect that a collision occurs, the participants generate a collision enforcement signal. The enforcement signal lasts as long as the smallest frame size. In the case of Ethernet, that equates to 64 bytes. This ensures that all stations know about the collision and that no other station attempts to transmit during the collision event. If a station experiences too many consecutive collisions, the station stops transmitting the frame.