2

enter image description here

So... I have a set up as below. I ping PC7 from the router. obviously an ARP is sent to determine PC7's MAC address. but it doesnt work. i then decide to set packettracer to simulation mode. i ping pc7 again and then. i notice that the switch drops the arp for some reason. I dont get why. someone out there in the world should know why.

enter image description here

notice how it says gigabit ethernet is blocked by STP. It seems i lack in understanding of STP. some wiser being please save me.

since i think its an issue on the switch. here is its running-config 




!
!
!
spanning-tree mode pvst
spanning-tree extend system-id
!
interface FastEthernet0/1
 switchport access vlan 10
 switchport mode access
!
interface FastEthernet0/2
 switchport access vlan 32
 switchport mode access
!
interface FastEthernet0/3
 switchport access vlan 64
 switchport mode access
!
interface FastEthernet0/4
 switchport access vlan 96
 switchport mode access
!
interface FastEthernet0/5
!
interface FastEthernet0/6
!
interface FastEthernet0/7
!
interface FastEthernet0/8
!
interface FastEthernet0/9
!
interface FastEthernet0/10
!
interface FastEthernet0/11
!
interface FastEthernet0/12
!
interface FastEthernet0/13
!
interface FastEthernet0/14
!
interface FastEthernet0/15
!
interface FastEthernet0/16
!
interface FastEthernet0/17
!
interface FastEthernet0/18
!
interface FastEthernet0/19
!
interface FastEthernet0/20
!
interface FastEthernet0/21
!
interface FastEthernet0/22
!
interface FastEthernet0/23
!
interface FastEthernet0/24
!
interface GigabitEthernet0/1
 switchport trunk allowed vlan 10,32,64,96
 spanning-tree portfast
!
interface GigabitEthernet0/2
!
interface Vlan1
 no ip address
 shutdown
!

Improve this question
4
  • You need to post the full configurations in order for us to help.
    – user36472
    Apr 18, 2018 at 10:52
  • i'm on it......
    – Frankline
    Apr 18, 2018 at 10:59
  • i had configured all the ports with spanning-tree portfast command i thought that was the problem so i negated the command @JFL
    – Frankline
    Apr 18, 2018 at 11:03
  • How is the router configured?
    – user36472
    Apr 18, 2018 at 11:41

2 Answers 2

Reset to default
2

Yeeei. I'm so thrilled i found my mistake. I didn't makeg that port on the switch to the router a trunking port... i'm so sorry i didn't tell you guys about all the VLANS i had in there... i see how there was no way you could have seen that. anyways:


!
interface GigabitEthernet0/1
 switchport trunk allowed vlan 10,32,64,96
 spanning-tree portfast
!

this plase should have been: 

! 
interface GigabitEthernet0/1
   switchport mode trunk
   switchport trunk allowed vlan 10,32,64,96 
   spanning-tree portfast 
!

Thank you guys for trying to help me here. it would have depressed me to death. you saved my life

Improve this answer
2
  • That is why you need to give us the full configurations of the network devices when asking such question.
    – Ron Maupin ♦
    Apr 18, 2018 at 15:47
  • Also, please accept your answer so that the question doesn't keep popping up forever, looking for an answer.
    – Ron Maupin ♦
    Apr 18, 2018 at 17:44
1

You just need to wait for the port to goes in forwarding mode.

By default on Cisco switches (and it seems in packet tracer), when a port goes UP, the STP process block the port until it determines that the network is loop-free, by listening for BPDU on this port.

To avoid this you can configure ports that are connected to hosts (I.E. not other switches) with the spanning-tree portfastcommand.
This will cause the port to goes in forwarding mode immediately upon connection, but still run STP discovery and block the port if a loop is detected.

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3
  • i had configured all the ports with spanning-tree portfast command i thought that was the problem so i negated the command
    – Frankline
    Apr 18, 2018 at 11:24
  • Sooo.... thats not the issue here.... but you could still help me figure this out. its killing me
    – Frankline
    Apr 18, 2018 at 11:25
  • @Frankline Ok but did you wait long enough for the port to transition in the forwarding state?
    – JFL
    Apr 18, 2018 at 12:01

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