Unable to ping Hosts through Ethernet Trunk port

[Paul56]

Hi All 

Trunk port created on a 3650 switch, all Vlans show as correct using (sh int trunk), all switches use the same running config and have another Ethernet port/interface on the same switch connected & configured exactly the same way but allows hosts across all vlans to be pinged from the switch connected to this interface.

I have spent hours checking the configurations of the ports, switches, vlan trunking, VTP's of the switches connected to the Ethernet ports set trunks to the switch which can ping hosts and the one which cannot and have been unable to understand why the switch connected to the added switch is unable to see devices connected to it.

All management configurations can be be performed, and the management Vlan can be pinged, one difference noticed is when clicking the (Sh Port Address) through the management console no mac address is shown.

If I use the following show mac address-table int gi1/0/1, the mac address of host & vlan of which it has access to is shown, everything seems to show as correct and the same as the other configuration of the hundreds of switches on the network, only difference is the switch is connected via Ethernet to  fibre media converter at the switch location as a older switch required a 1Gb connection.

Note! this is the second connection from this switch to another switch connected in this way and have no issues with this first switch, all configurations are the same, but can ping and connect to hosts from this switch.

Has anyone got an possible reason why this is occurring, or had the same issue and resolved it, please advise as seem to be going round in circles.

[Elliot Dierksen]

Do you see mac addressees for the problem vlan?

show mac addr dyn vl X

 If so, then your problem is layer 3 routing. If not, then your problem is layer 2. The vlan could be blocked by STP, or some switch in the path doesn't have that problem vlan in its vlan database. Also, do you have VTP pruning on anywhere? Check that out along the L2 path in each switch this way.

show vtp status

 Make sure each one has the correct configuration revision too.

[Paul56]

Hi Elliot,

When performing the 

show mac addr dyn vl X

on the switch which has this issue it only see 2 mac addresses (1,on the port the device is connected to, the other being the trunk port, if performed on another switch shows all the mac addresses passes related to the interface and trunk interfaces it passes through on that switch.

On the switch which has the issue I cannot ping anything connected to it even if I am trying on the switch, but can ping out from the switch to any host on any vlan which there are many.

Checked the VTP Status of the switches and are all running the same revision, and show the same configuration part of the running config: 

spanning-tree mode pvst
spanning-tree etherchannel guard misconfig
spanning-tree extend system-id
!
vlan internal allocation policy ascending

!
vtp pruning
vtp version 2
vtp mode transparent
vtp mode client
vtp domain **********
vtp password *********

All switches have the same running config just the one has this issue, appreciate your help

[Paul56]

Hi Elliot,

When performing the: show mac addr dyn vl X 

on the switch which has this issue it only see 2 mac addresses (1,on the port the device is connected to, the other being the trunk port, if performed on another switch shows all the mac addresses passes related to the interface and trunk interfaces it passes through on that switch.

On the switch which has the issue I cannot ping anything connected to it even if I am trying on the switch, but can ping out from the switch to any host on any vlan which there are many.

Checked the VTP Status of the switches and are all running the same revision, and show the same configuration part of the running config: 

spanning-tree mode pvst
spanning-tree etherchannel guard misconfig
spanning-tree extend system-id
!
vlan internal allocation policy ascending

!
vtp pruning
vtp version 2
vtp mode transparent
vtp mode client
vtp domain **********
vtp password *********

All switches have the same running config just the one has this issue, appreciate your help

[MHM Cisco World]

when I design any network I use two line color 
green represent the L2 path 
red represent the L3 path 
in you case 
draw your network in paper, and use green line 
the green line which is L2 must pass to all SW if there is host connect to SW in same subnet of one VLAN 
what point to check here ?
1- VLAN is in all SW , here many mistack that allow VLAN meaning that VLAN will dynamic created and that not right, when we all VLAN in trunk in SW that not have access port assign to that VLAN the VLAN will not created automatic. 
2- VTP pruning, if you run VTP pruning than there is a chance that VLAN not allow in trunk 

must green line pass through all SW ?
NO, the green line will end if you want in one SW but instead you must sure to make host in different VLAN (subnet) connect to each other to draw red line 
red line in case of SVI is between SVI VLANx- SVI VLANy 

this way of troubleshooting never wrong and you can always use it.

[MHM Cisco World]

""on the switch which has this issue it only see 2 mac addresses""

so the VLAN is not UP, 
only do 
vlan x <<- this command add VLAN to SW 

and make double check the allow VLAN in all trunk in this issue SW