Spanning Tree Portfast - Video By Sikandar Shaik || Dual CCIE (RS/SP) # 35012

[Music] spanning-tree portfast now now in this video we'll see as feature a Cisco proprietary enhancement to the spanning tree to speed up the convergence on the access ports now if you just go back to the basic spanning tree behavior like the second example I have a switch which is connecting to some of the access ports now whenever I provide a connection on this particular board by default the port goes through listening and learning stages now this listening and learning stages is the default behavior because every port goes through a spanning tree verification where it is going to take some 30 seconds of time before it actually transitions into forwarding state so once it confirms that there is no possibility of loop or there is no BPD messages on this particular port and it's going to put the put into forwarding state but after 30 seconds now because of this default behavior of the spanning tree let's take an example I have there are some services which might get affected next second example I have some DHCP server here and probably whenever you power on the PC here it's connected on the port and whenever you power on the PC it's going to send some broadcast requests requesting a DHCP server to assigned IP roles and by the switch is not going to forward that particular messages till 30 seconds so which means you have a 30 second downtime by default on each and every access port and because of that downtime this there might be cases like some of the services like DHCP service request may not reach the DHCP servers and there is something with little water now let's verify the default behavior I'm going to connect this PC on port number 1 and if I go to the command line and verify the default behavior of the spanning tree here if I give show spanning tree you can see the port number 1 which I connected to the end host is going through some listening set and after some time you see the port goes into learning before it actually transitions into forwarding I can see the port is in ramble now now it turns to green now the poor transitions into forwarding that is the default behavior now we actually don't want this behavior now what we can do is we can add some enhancement to the default voluntary behavior where on this particular access port we can disable an entry so in fact we are not deserving spanning tree we can say we we are going to enable sport fast feature which will allows the particular access port to transition into forwarding immediately without listening without learning bypassing the listening and learning stages so which means once you enable port fast this particular ports will not go through with listening and learning stages so there is no more listening learning stages and the transitions immediately into powering so when you enable for pass it means automatically you are disabling the spanning tree on that particular course and you need to be very careful because if you do this on the port which is connecting to a switch or a half or any other device will there is a possibility of loose so you know it's really not you need to just keep in mind that you should know you enable the port fast on the port which are connecting to the switches or half because it can cause temporary rules so poor pass has to be enabled on the port which is connecting to a single end station and if you are going to enable the port first on a port which is connecting to another networking device it can cause a temporary loop so that's something we need to ensure that we are not enabling the port fast on the links connecting the switches so once you enable port fast so administrated is going to ensure that these ports they are not connecting to any end une networking devices or to switch or a hub and we are saying that these are connecting to the end devices and there is no possibility of loop now this way we can save that 30 seconds downtime initially for access now to enable the port passed on the access port either we can go to the specific interface and we can na by using a range command if you if you want enable on multiple ports we can give a command called spanning-tree portfast on the interface pacific or we can enable the same command globally so by using this command called spanning-tree portfast default now if you are going to enable the port fast or globally in the global conversation mode it is going to make each and every access port will automatically will be enabled with a port fast feature which means the trunk links will not be converted as export fast every access port will automatically become a port fast port so either we can define a specific interface or we can make every access port to go into port website so let's go to the command line here for verification I am going to switch one and I am going to configure interface range as if I want to them so I'm assuming that the first ten ports are going to be connected to my end devices and then I am giving a command called spanning-tree portfast so once you enable this planning report fast you can see there is a warning message which says that the poor path should be enabled only on the port which is connecting to a single host and if you have any given age if this particular food is connecting to half concentrators switches bridges any of the networking devices it's going to create some temporal will do it's just a warning message and then it says that the port fast has been configured on this 10 interfaces due to the range command which we have used and four points will have only effective when the interfaces are in norm cranking mode so right now these ports are not in a 20 mode so now for verification what I can do is I can have some connections on the end devices on port number two for number three and port number four and I can go and verify which show spanning tree I can see port number 2 3 4 immediately transitions into poverty state without listening and without learning so this is how we can optimize it's a cisco proprietary feature or of speeding up the convergence on the accessport and it can be enabled either interface specific mode or global configuration mode so depending upon the requirement part of the competition you can either you can go with any one of this configuration both will have the same same impact on the switches [Music]

Channel: Sikandar Shaik

Views: 36,767

Keywords: ccna, ccna videos, noa, noa videos, stp, stp portfast, ccnp, cisco, ccie, subnetting, ccna security, bgp, ospf, firewall, ccna subnetting, ipv6, bgp videos, ccna vdieos, ccna free video, ccie certification, ios, iou, virtual, eigrp, cisco virtual lab, iosv, asav, gns3, routing, noa vdieos, noa solutions, zone based firewall, zone pair, zbf, flsm, cisco firewall, cisco security, cisco certifications, wan, ip addressing, netmetric, vlsm, eigrp configuration, vlan, ccnp, cisco

Id: tUJYuwSSVE4

Length: 7min 10sec (430 seconds)

Published: Thu Jan 19 2017