How to speed up the process of switching port initialization

When connecting a computer to a switch, it may take 30 seconds or more for the computer to communicate with the network. If you are in a hurry to use, 30 seconds of waiting is enough to make you feel very long. Let's see how we can speed up the port initialization process for the switch.

Understanding the process of switch port initialization

When you connect a device to a port on a switch that has already been started, the switch port typically undergoes 4 steps. Let's take a closer look.

Spanning Tree Protocol (STP) initialization

STP is an IEEE 802.1D protocol that prevents the formation of loops in a local area network. Testing This switch port is necessary; When you start the STP, a loop is formed within the LAN. STP is especially important if you are connected to a hub, switch, or router. On the other hand, if connected to a computer, printer, server or a laptop, then the STP initialization process is not needed.

In the middle of the STP initialization phase, ports experience 5 stages of STP: blocking, listening, learning, forwarding, and expiration. The whole process takes 15 seconds. So, if you're sure what you're going to connect to, you can terminate the process.

Ethernet Channel Configuration Test

The next process is a test of the Ethernet channel, which is bound to the switch port to provide more Ethernet connectivity. If one channel does not work, the Ethernet channel usually provides redundancy. This process uses the Port aggregation Protocol (PAGP), which takes about 15 seconds.

Trunk configuration test wired and wireless networks

Next, the switch begins testing the port for trunk ports (the ports used to interconnect between switches). Trunking Exchange data between multiple VLANs through a single switch port. Testing the trunk port is time-consuming, but you can also ban it and save 1 or 2 seconds.

Switch port speed and full duplex adaptive

Finally, switch ports enter the automatic handshake with full duplex speed. For example, a switch port can support a 1000Mb (1Gb) Full-duplex speed, but the client only supports 100Mb Full-duplex, and the switch and client automatically negotiate the highest rate that each can support.

This process can be hard-coded to save time during the switch initialization process. But this is not always a good choice, because you may not know how fast the client support is going to be. This adaptive time is not long, so you might want to consider carefully if it is worth the time to hard-code each switch port.

Now that we've reviewed the different stages of switch port initialization, let's see how much time we can save from it.

Perform the following steps to save the port initialization time of more than 30 seconds for a switch based on the Cisco IOS Protocol:

Set the switch port to access mode. This cancels the trunk negotiation and prevents the port from entering the Ethernet channel negotiation. This can save 15 seconds for the initialization process.

Configure Portfast. This will prevent the port from entering STP negotiation and save another 15 seconds.

Here's an example:

Switch(config)# int fa0/21Switch(config-if)
# switchport mode access Switch(config-if)
# spanning-tree portfast%Warning:
Only enable PortFast on ports connected to a single host.
Connecting hubs, concentrators, switches, bridges, etc.
to this interface when you've PortFast
can cause temporary bridging loops.
Use with CAUTION.%This has configured PortFast
on FastEthernet0/21 but will only have an effect when
the interface is in a non-trunking mode.
Switch(config-if)# no shutdown Switch(config-if)#

You can also set on a series of ports, such as:

Switch(config)# int range fastEthernet 0/1 - 24Switch(config-if-range)
# switchport mode accessSwitch(config-if-range)
# spanning-tree portfast

If you feel the need, you can also artificially set the speed of the switch port, save a little time. Here is an example.

Switch(config-if)# speed 100Switch(config-if)# duplex full

By prohibiting STP initialization, trunk negotiation, Ethernet channel negotiation can save 30 seconds for the initialization process. In addition, you can use the scope command of the interface to set all ports of the switch.