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This site uses cookies. Ok thanks Cookie policy. Port will actively attempt to bundle ports in the group-channel with a PAgP enabled neighbour, either in auto mode or negotiate. Port will passively wait for the neighbour to negotiate a PAgP session for bundling ports. As you can see from our modified topology, the three fastEthernet Links have been bundled up into a single logical connection which is port-channel 1. In the CCNA curriculum, you will not be expected to configure an ether-channel for your exam, however, you are expected to understand the concepts behind it and it is a very useful concept in real world situations as well as in the CCNP level.
We will configure ether-channel using the scenario shown below and see how it works as well as some verification and troubleshooting commands.
In the above scenario, we are supposed to configure ether channel on the links shown. The switches are using their default configuration, and the first thing we need to verify is the number of links that are active in the topology and whether STP is blocking redundant paths.
All the ports on DS1 are active since this switch was elected the root bridge. Successful configuration of the ether-channel will mean that the blocked paths will be transmitting data and will be root ports by the end of the configuration.
NOTE: when the channel-protocol command is used and a negotiation protocol is enabled, the options on the channel-group command, will be limited to the options available for that protocol ONLY.
When negotiating an aggregated link, the protocols will follow rules similar to those of negotiating trunk links as shown in the table below. Next we need to configure the mode of operation as well as specify the logical port number for the ether channel. For this we use the command. In our case the logical number will be 1 and the mode will be desirable on both switches as shown below. As you can see from the output of DS2 above, the new interface is port-channel 1, which is active and forwarding.
Our solution to this problem? EtherChannel aggregates or combines traffic across all available active links, which makes it look like one logical cable. So in our example, if we have 8 active links with Mbps each, that will be a total of Mbps. If any of the physical links inside the EtherChannel go down, STP will not see this and will not recalculate.
Since more than one physical connection is combined into one logical connection, EtherChannel enables more available links in instances where one or more links go down.
With load balancing, we are able to balance the traffic load across the links and improves the efficient use of bandwidth. In this example, we connected 2 switches, Switch1 and Switch2, using four links. What do you think will happen without EtherChannel? You can see in the network topology below the link states, only one link is being utilized.
If we enable EtherChannel on the links of the switches, you can see that the link states for all of the links are up. Meaning, we can utilize all of the 4 links and reap the benefits of EtherChannel namely, load balancing, redundancy, and increased bandwidth. These commands are used to enable EtherChannel.
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