Refer to the exhibit. All switches are configured with the default port priority value. Which two commands ensure that traffic from PC1 is forwarded over the Gi1/3 trunk port between DSW1 and DSW2? (Choose two.)
Refer to the exhibit. All switches are configured with the default port priority value. Which two commands ensure that traffic from PC1 is forwarded over the Gi1/3 trunk port between DSW1 and DSW2? (Choose two.)
To ensure that traffic from PC1 is forwarded over the Gi1/3 trunk port between DSW1 and DSW2, you need to configure the port priority on DSW2. Since all switches are configured with the default port priority value, you need to set a lower port priority on the relevant interface of DSW2 to influence the spanning-tree path selection. Port priority is configured in increments of 16, and the default value is 128. Setting the port priority to a lower value on DSW2 will make its interface more preferred. Therefore, you should open the interface configuration on DSW2 and set the port priority to a lower value, such as 16.
The correct answers would look to be A & E. Priority is chosen based on the upstream port, therefore we need to make this change on DSW2. This means answers B and D are out. Port priority is set in increments of 16: Switch(config-if)#spanning-tree port-priority ? <0-240> port priority in increments of 16 This leaves us with C or E. C is the default, so won't change the behaviour here, so it's out too. The only two still standing are A & E.
DSW2 is root bridge. Port-priority always change on far end switch for root port & blocking port which is SW1. B & D are correct.
far end from root PORT. not from root bridge. AE is the correct answer
I trust the answer from Mac13. If you change port-priority, you do it on designated ports/upstream devices. (i.e. DSW2) If you would change DSW1, you would have to work with port costs on root ports/downstream devices. Source: https://community.cisco.com/t5/routing/spanning-tree-with-port-priority/td-p/1815059
you are right, i was using an IOS switch en eve ng and the incremnt is 64
DSW2 is the Root Bridge, so everything should be observe from its point of view. STP works in the following way: 1. Root Bridge election >>> all ports on the RB are designated 2. Root Port election each switch from its perspective chooses the best path cost to the root bridge. election criteria is the port cost, which consists of: 1-port priority (0-255) 2-port number the only thing that we can manipulate to change the STP result is changing the port cost of Gi1/3 of the DSW1.
Actually, AL SW2 is the RB since MAC 0013 < 0018
RB election based on lowest BID > lowest MAC
Correct Answer here is B, D DSW2 will be elected as root bridge. So all the ports of a root bridge are in forwarding mode. DSW1 has to make the decision to block redundant ports. Default port priority is 128, so interface number breaks the tie. In this case Gi1/3 on DSW1 will be blocked. To prefer Gi1/3 over Gi1/2 the port priority has to be lower than 128. the most appropriate answer is DSW1(config-if)#spanning-tree port-priority 0. Before applying this command you need to apply DSW1(config)#interface gi1/3 The priority values are 0, 32, 64, 96, 128, 160, 192, and 224. All other values are rejected. https://www.cisco.com/c/m/en_us/techdoc/dc/reference/cli/n5k/commands/spanning-tree-port-priority.html#:~:text=The%20priority%20values%20are%200,is%20the%20default%20STP%20mode.
Make sense
Yes u r right
Correct ans are B and D. Small clarification regarding port priority values. In ENT Core exam we learn about IOS-XE not IOS-XR (n5k). IOS-XE: 'For priority, the range is 0 to 240, in increments of 16; the default is 128. Valid values are 0, 16, 32, 48, 64, 80, 96, 112, 128, 144, 160, 176, 192, 208, 224, and 240. All other values are rejected. The lower the number, the higher the priority.' https://www.cisco.com/en/US/docs/switches/lan/catalyst3650/software/release/3se/consolidated_guide/configuration_guide/b_consolidated_3850_3se_cg_chapter_01001001.html#ID828
I confirm B,D tested on GNS3 lab
DSW2(config)#interface gi1/3 DSW2(config-if)#spanning-tree port-priority 16
In the DSW1,DSW2,ASW1,ASW2 STP domain the DSW2 has the best prio:24576 port priority has to be modified on the upstream switch (DSW2).
You should open the interface you want to configure. "A" opens the correct interface and "E" configures it. AE are the correct answers
Is the only answer I can see that makes sense
One thing we can all agree on, can't be DE as given answer says. D is starting configuration on SW1, E continues the interface configuration on SW2. Mismatched pairs. Only choice pairs that can be chosen are AE or BD. Choice C is default port priority so that's out if you think you should configure SW2, not relevant if you think you should configfure SW1. I misread the text saying all PORT priorities are at defaults, thinking it said all switch priorities are defaults, though the exhibit shows the two distribution switches have different priorities. Either way, switch priorities same or as exhibited, bridge MAC makes SW2 root. That makes all its ports designated, so it is SW1 that needs to decide whether either of the ports between then are RP or blocked. Only way to do this is by setting port priority. But SW1 will be going by the port priority it sees reported by SW2, NOT by what SW1 ports are set to. So must make configuration change at SW2. Answer therefore must be AE
A and E
Lab with EVE-NG, I attempt to change the port priority on DSW1 Gi1/3 the port-priority to 0 but it didn't work. While change the port-priority on DSW2 Gi1/3, it took effect. So the Answer should be A,E.
UPSTREAM (root) switch interface towards DOWNSTREAM switch configured with prior 64: sw1#show running-config interface Po2 Building configuration... Current configuration : 179 bytes ! interface Port-channel2 switchport switchport trunk encapsulation dot1q switchport trunk allowed vlan 1-9,11-4094 switchport mode trunk spanning-tree port-priority 64 end sw1#
this is ROOT port from DOWNSTREAM switch perspective (see Po2 int): sw2#show spanning-tree vlan 30 VLAN0030 Spanning tree enabled protocol rstp Root ID Priority 32798 Address aabb.cc00.1000 Cost 100 Port 65 (Port-channel2) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 32798 (priority 32768 sys-id-ext 30) Address aabb.cc00.4000 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300 sec Interface Role Sts Cost Prio.Nbr Type ------------------- ---- --- --------- -------- -------------------------------- Et0/0 Desg FWD 100 128.1 Shr Edge Et0/3 Altn BLK 100 128.4 Shr Po2 Root FWD 100 128.65 Shr sw2#
remove priority from UPSTREAM swith: sw1#conf Configuring from terminal, memory, or network [terminal]? Enter configuration commands, one per line. End with CNTL/Z. sw1(config)#interface Port-channel2 sw1(config-if)#no spanning-tree port-priority 64 sw1(config-if)# sw1(config-if)#do show spanning-tree vlan 30 VLAN0030 Spanning tree enabled protocol rstp Root ID Priority 32798 Address aabb.cc00.1000 This bridge is the root Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 32798 (priority 32768 sys-id-ext 30) Address aabb.cc00.1000 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300 sec Interface Role Sts Cost Prio.Nbr Type ------------------- ---- --- --------- -------- -------------------------------- Et0/0 Desg FWD 100 128.1 Shr Et0/3 Desg FWD 100 128.4 Shr Po2 Desg FWD 100 128.66 Shr sw1(config-if)#
root port has been changed on DOWNSTREAM switch from Po2 -> E0/3: sw2#show spanning-tree vlan 30 VLAN0030 Spanning tree enabled protocol rstp Root ID Priority 32798 Address aabb.cc00.1000 Cost 100 Port 4 (Ethernet0/3) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 32798 (priority 32768 sys-id-ext 30) Address aabb.cc00.4000 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300 sec Interface Role Sts Cost Prio.Nbr Type ------------------- ---- --- --------- -------- -------------------------------- Et0/0 Desg FWD 100 128.1 Shr Edge Et0/3 Root FWD 100 128.4 Shr <<<<<<<<<<<<<<<<<<<< root port Po2 Altn BLK 100 128.65 Shr sw2#
A & E are correct
If you think BD is right, please read Asymptote explantion. For sure AE is the only option. If you still think BD you misunderstand the fare end port priority.
A&E are the correct answers
the answer is A/E. the reference: https://www.ciscopress.com/articles/article.asp?p=2995351&seqNum=2
The correct answer is A&E
I am having a tough time with this one. The answer can be B or E. (but definitely A) DSW2(config-if)#spanning-tree port-priority ? <0-240> port priority in increments of 16 you can actually set it to 0 or 16 and DSW1 will see it as a root port. Interface Role Sts Cost Prio.Nbr Type ------------------- ---- --- --------- -------- -------------------------------- Gi1/2 Altn BLK 4 128.1 P2p Gi1/3 Root FWD 4 128.2 P2p So im not too sure what the right answer is.
You're all mistaken. To change the port priority on a switch you have to change the adjacent port on the upstream switch. It's B&D. It's page 64 of the OCG.
Upstream from root bridge, not upstream from packet stream. Direction of frames has no bearing on what STP blocks or doesn't blocks.
Read it again. You will figure it out. it is A & E. "Both the port priority and port number are controlled by the upstream switch" in this case DSW2.