Portsecurity can be used to protect switches from some l2 attacks like mac flooding. Cisco enterprise network compute system switch command. Occasionally a hardware or software failure can cause stp to fail, creating stp forwarding loops that can cause network failures where unidirectional links are used. Configuring switchport spanning tree portfast free ccna.
Stp switches exchange bridge protocol data units bpdus to build the topology database. With bpdu filter any incoming bpdus are simply dropped, but the switch port is not disabled. Use the following commands to enable or disable stp bpdu guard on fortiswitch ports. What could be the reason that the fa02 interface is shutdown. For example, if you want to reenable protected ports 60 seconds after receiving a bpdu, you would use this command. The port led is set to the orange color and, when you issue the show interfaces command, the port status shows as errdisabled. Building the stp topology is a multistep convergence process. The no form of the command disables stp loop guard. This command is executed in privileged mode to display the current status of default stp configurations including portfast. Root guard is enabled with the interface command spanningtree guard root.
Bpdu guard is usually configured on access layer ports where we are not expecting to see any bpdu packets arriving from devices connected to these ports e. Following is an example of what an errordisabled port looks like. The bpdu guard feature can be globally enabled on the switch or can be enabled per port, but the feature operates with some differences. Bpdu guard is enabled globally on all stp portfast ports with the. Configuration vlans, spanning tree, and multilink trunking avaya ethernet routing switch 4500 series 5. In this scenario, the default src mac could be left on sw2, but sw1 would need to be changed to dst mac or srcdst mac to perform best practice load balancing. However, when you enable this feature on an interface, it applies to that interface regardless of the spanning tree port type. This command is executed in interface configuration mode and is used disable bpdu guard which can be enabled by default by using the command above. This command is executed in interface configuration mode and enables bpdu guard on that specific interface. Bpdu protection 5 ei switches probably, configxxxxx shows configured value, whereas. If the link type of the port is trunk and the port has been added to vlan 1, the cisco switch can interwork with the s series switch in vlan 1 only.
What is bpdu guard and how to configure bpdu guard in cisco switches bpdu guard feature is used to protect the layer 2 spanning tree protocol stp topology from bpdu related attacks. This feature is one of the spanning tree protocol stp enhancements that cisco created. When you enable this bpdu guard command globally, the command applies only to spanning tree edge ports. So bpdu guard is used to protect the switch from an attacker that connects into the network via a switch port. Question which two network design features require spanning tree protocol stp to ensure correct network operation. When bpdu guard shuts down a port due to bpdus being received on the port, the port will be placed into a shutdown state known as errdisabled. See the difference below, to enable bpdu guard globally, perform this task.
Configuring spanning tree portfast, bpdu guard, bpdu filter. Root guard prevents the interface from becoming the root port of the device. Aggressive mode udld cannot detect failures caused by problems in software in the designated switch not sending the bpdu. If your example 1 a new distribution switch is plugged in with a superior bpdu would happen. The stp portfast bpdu guard enhancement allows network designers.
Sep 01, 2005 this document explains the portfast bridge protocol data unit bpdu guard feature. When the switches receive this message they will reduce the aging time of the mac address table from 300 seconds to 15 seconds this is the forward delay timer. Hi kevin, check whether you have the bpdu guard enabled globally using the spanningtree portfast bpduguard default global configuration command. Bpdu guard feature must be enabled on a port that should never receive a bpdu from its connected device. Root guard will stop a superior bpdu from becoming the root. The mstpd daemon is an open source project used by cumulus linux to implement ieee802. Listening and learning are transitory port states, used only when moving from the blocking to. Cisco 2960s and shutting down ports with a duplicate mac. Note for information on configuring spanning tree, see chapter 7, configuring spanning tree.
Even if some of the vmware release notes and publications for esxi 5. Ports not receiving a bpdu packet within a hello time period enter inconsistent blocking state. The fa024 interface of s1 is configured with the same mac address as the. Portfast is a cisco network function which can be configured to resolve this problem. Stp etherchannel bpdu misconfig guard, layer 3 etherchannel, and etherchannel loadsharing labbed.
Tcn guard enabling the tcn guard feature restricts the port from propagating any topology change information received through that port. Why not just configure bpdu guard on all access layer ports and be done with it. Apr 01, 2020 spanningtree guard root to enable root guard on all spanningtree instances on an interface, use the spanningtree guard root command in interface switch configuration mode. Bpdu protection for spanningtree protocols techlibrary. If that is the case then on the individual port, the bpdu guard can be disabled using the spanningtree bpduguard disable command if the port is indeed errdisabled thanks to the bpdu guard check the cause of the errdisabled state using the show. Apr 19, 2020 bpdu guard is an stp enhancement which, when enabled, will place a port in the errdisable mode when it receives any bpdu packet from that port. A root bridge is elected root ports are identified. The fa02 interface on switch s1 has been configured with the switchport portsecurity mac address 0023. What is root guard and how to configure root guard in cisco. Spanning tree bpduguard and errdisable interface automatic. The following section describes some of the layer2 spanning tree protocol stp features for the branch controller solution. I am going to setup the following security measures bpdu guard, root guard and port security and use the kali linux box in my topology to launch attacks fun times.
A broadcast address will never be the source address. Assuming that all access ports have portfast enabled, this ensures that a loop cannot accidentally be created if an unauthorized switch is added to a topology. Example for configuring stp all about switches huawei. See the spanningtree port type edge bpdufilter default command for more information on the global command for bpdu guard. If you disable bpdu guard you really should use portsecurity with a mac address limit as a fallback for loop prevention. Nov 19, 2012 as you might know by now, with the release of vsphere 5.
This factor of time is not an issue for many people, but it can cause problems for some. The time spanning tree protocol stp takes to transition ports over to the forwarding state can cause problems. Console enable set spantree portfast bpdu guard enable spantree portfast bpdu guard enabled on this switch. The spanningtree protocol is used to cut loops that redundant links create in bridge networks. Stp root guard, bpdu guard, and bpdu filter mechanics, behaviors, and verification labbed. Spanning tree and rapid spanning tree cumulus linux 3. Below configuration commands enable bpdu guard by default on all portfast edge ports. The guide says that the protection column should be bpdu, if you have bpdu guard on. This means that even if a port receives a bpdu with the topology change flag set to true, the port will not flush its mac address table and send out a bpdu with a topology change flag set to true. Bpdus are forwarded out all ports every two seconds, to a dedicated mac multicast address of 0180. Port link state dupl speed trunk tag pvid pri mac name 1114 errdis. To return to the default setting, use the no form of this command.
Bpdu guard this port will be disabled and move to an errdis state. Both commands are used for the bpdu guard globally by default on all edge ports of the switch only. With bpdu guard, when a portfast receives a bpdu, it will be shut down to prevent a loop d is correct. Bpdu guard is a safety mechanism that shuts down ports configured with stp portfast upon receipt of a bpdu. Bpdu guard is used when a port is configured for portfast, or it should be used, because if that port receives a bpdu from another switch, bpdu guard will shut that port down to stop a loop from occurring. To shut down an interface if it receives a loopback bpdu, use the spanningtree loopback guard command in switch configuration mode.
These features are not dependent on each other, can be applied either together or independently. Stp root guard, bpdu guard, and bpdu filter mechanics. This factor of time is not an issue for many people, but it can cause problems for. To restore the default configuration, use the no form of this command. You can use errdisable recovery cause bpduguard command to do this. Enter the set spantree guard command to enable spanning tree loop guard on a perport basis. I like to use the show mac addresstable dynamic command so we dont have to browse through a list of static mac addresses. Spanning tree and bpduguardfilter will it affect my trunk. Enable mx series router to participate in the provider rapid spanning tree protocol rstp instance or a provider. How to configure bpdu guard globally at global configuration mode. Ports disabled by bpdu protection remain disabled unless bpdu protection is removed from the switch or by configuring a nonzero bpdu protection timeout. Enabling bpdu guard feature on a trunk port that forms the stp topology is also not recommended. Finding mac address of an offending device that triggers bpdu guard im trying to detect an offending mac address of a device that is connected to a user lan port. We can confirm the traffic path by looking at the mac address table.
Configuring switchport spanning tree bpdu guard free. This value will change to indicate its a topology change notification. Jun 02, 2015 mst is the cisco implementation of mstp, an ieee standard protocol that provides up to 16 instances of rstp and combines many vlans with the same physical and logical topology into a common rstp instance. If any changes occur in the layer 2 network, such as when a link goes down, a new link is added, a new switch is added, or a switch fails, the switches share this information by transmitting bpdus, causing the stp algorithm to be reexecuted, and a new loopfree topology is then created. Finding mac address of an offending device that triggers. Posted on december 21, 2017 august 27, 2019 by loopy in this topology everything is default, so sw1 has one the root bridge election with the lowest mac address as the tie breaker, and all port states were dynamically calculated. When a bpdu guard enabled port receive bpdu from the connected device, bpdu guard disables the port and the port state is changed to errdisable state. What additional information is contained in the 12bit extended system id of a bpdu. The most noticeable difference between aggressive mode udld and loop guard is with regard to stp. I was having a problem with mac flapping so opened a ticket with cisco tac the vlan interface on the core was the mac that was flapping. Catalyst 2960 and 2960s switch command reference, 12. Again just like bpdu guard you can configure the switch to automatically bring the port back up.
If the other side of the link has bridge assurance enabled, or if the other switch is the root bridge, it will send periodic bpdus, preventing an inconsistent. Spanning tree protocol stp is always recommended in layer 2 topologies, as it prevents bridge loops and broadcast radiation on a bridged network. In the same topology, assume that bpdu guard is configured on access switches interfaces to hosts, root guard is configured on distribution switches interfaces to access switches, and core switches interfaces to distribution switches. The required commands for part 4 are provided in appendix a. Root guard in conjunction with portfast, and bpdu guard is used to prevent an stp manipulation attack. Mst is the cisco implementation of mstp, an ieee standard protocol that provides up to 16 instances of rstp and combines many vlans with the same physical and logical topology into a common rstp instance. Oct, 2008 on access ports with portfast enable bpdu guard. Bpdu guard, errdisabled and ip phone cisco community. For example, when someone adds a new switch to an access port off a leaf switch and this new switch is configured with a low priority, it might become the new root switch and affect. The bpdus are not forwarded, and the network edge is enforced. Currently, portfast and bridge protocol data unit bpdu guard features are supported, which work along with existing l2 stp feature. This command is executed in privileged mode to display a table of ports assigned to a particular vlan and the current port status rather its fwd or blk. In this case, the show spanningtree transmit active command will show a bridge assurance status of inconsistent for the port. When bpdu guard is enabled on stp edge ports, any bpdus received cause the ports to go down for a specified number of minutes.
Portfast bpdu guard prevents loops by moving a nontrunking port into. The bpdu guard transitions the port into errdisable state, and a message appears on the console. As youll notice in the observation of spanningtree the port is first blocking all traffic, then learning which still blocks traffic but learns mac addresses from frames and processes bpdus from connected devices to determine potential switching loops then finally the port is placed into fwd forwarding if no layer two loop is detected. This command should only be used to guard edge ports that are not expected to participate in stp operations.
Catalyst 3560 switch software configuration guide, release. This chapter describes how to configure the portfast, bpdu guard, bpdu filter, uplinkfast, backbonefast, and loop guard spanning tree enhancements on the catalyst enterprise lan switches. To return to the default settings, use the no form of this command. What i cant find any good documentation on is mixing bpdu filter and bpdu guard as global defaults with ports configured for portfast trunk. At the global level, you enable bpdu guard on port fastenabled ports by using the spanningtree portfast bpduguard default global configuration command. To reset this, navigate to the interface and bounce the interface shutdown the interface then bring it back up. With bpdu guard, when a portfast receives a bpdu, it will be shut down to prevent a loop d is. Spanning tree portfast bpdu guard enhancement cisco.
Each instance supports portfast, bpdu guard, bpdu filter, root guard, and loop guard. Note for complete syntax and usage information for the commands. Oct 26, 2012 hi, why would you choose one over the other. To enable bridge protocol data unit bpdu guard on an interface, use the spanningtree bpduguard command. Still, every portfast enabled port that receives bpdus loses its portfast status until disconnected. Instance priority mac addr cost time age dly root port. Bpdu guard can be enabled on all portfastenabled ports by using the spanningtree portfast bpduguard default global configuration command. I have three other ports on the same switch that are now in errdisabled state because they received bpdu s. Configuring bpdu protection on a device huawei technical support. This message is called the tcn topology change notification. You can also configure bpdu guard as a default setting for spanningtree on all. When bpdus again are received on the inconsistent port, it resumes normal stp operation. The following commands are executed on interface fa01 of 2950switch. As i can understand, bpdu drop just discarding bpdu s, but they still forwarding thru port.
At the reception of bpdus, the bpdu guard operation disables the port that has portfast configured. These packets are not attested by the system, so an attacker could spoof the bpdu and compromise the network stability see below to understand bpdu attack in this example the ciscozine1 switch is elected root bridge due to the lower mac address suppose that all the switches have the same. Im going to configure port security on port gi11 so it will shut the port down after it receives more than 5 mac addresses. Alternatively, bpdu guard can be enabled on a portfastenabled port through the use of the spanningtree bpduguard enable interface configuration command. Similar to root guard, bpdu guard protects the designed network topology. Broadcast addresses use an incorrect format for the switching table. You can enable the bpdu guard feature when the switch is operating in the pervlan. Configuring switchport spanning tree bpdu guard free ccna. If a bpdu is received on a bpdu guard port, portfast is used to shut down the port. To set all the ports on the switch, use the set spantree mst globaldefaults loopguard command. We have configured our edge ports using the following commands but when you do a display stp brief it tells me that the protection is none. In addition to bpdu guard enhancement wed like to enable duplicate mac sniffing or something of the sort so that if a duplicate mac address shows up on the network the switch will shutdown the port with the duplicate mac automatically to kill any looping before it can become an issue. First posting so please be nice j i am getting really confused regarding stp, loopprotection, and bpdu.
Can someone help me with the config for edged port bpdu protection on the 5. Spanning tree is used to ensure a loopfree topology over the lan. To enable bpdu guard globally on the switch, use this command. In which two port states does a switch learn mac addresses and process bpdus in a pvst. What is bpdu guard and how to configure bpdu guard in cisco. I talked about the new features briefly in the whats new paper and also posted evaluation videos on some of the key features. When a port is in errordisabled state, it is effectively shut down and no traffic is sent or received on that port. Study 41 terms spanning tree protocol flashcards quizlet. What is bpdu guard and how to configure bpdu guard in.
Optional enable mac address change notification traps. To only disable a vlan that receives a bpdu when bpdu guard is enabled, we can set the errdisable detect cause bpduguard shutdown vlan command. Configuring spanning tree portfast, bpdu guard, bpdu. You can configure bpdu guard bridge protocol data unit to protect the spanning tree topology from unauthorized switches affecting the forwarding path. Bpdu guard will stop another switch from connecting entirely by shutting the port down. The student uses the wifi router to connect her laptop, smart phone, and dvd player.
How to protect against bpdu attack ciscozine ciscozine. This feature enhances switch network reliability, manageability, and security. So, upon receiving a bpdu on your port, the port will lose both bpdufilter and portfast states but both are the direct consequence of receiving a bpdu. Once bpdu protection is enabled, it will disable the port as soon as any bpdu packet is received on that interface.
Spanning tree and rapid spanning tree cumulus linux 4. Additional stp protection mechanisms advanced stp tuning. Catalyst switches detect a mac address that is flapping between interfaces. Understanding bpdu protection for spanningtree instance interfaces, understanding bpdu protection for stp, rstp, and mstp, configuring bpdu protection for individual spanningtree instance interfaces, understanding bpdus used for exchanging information among bridges, bpdu protection on all edge ports of the bridge, understanding bpdu protection for evpnvxlan, configuring bpdu protection on.