Interswitch same Vlan host communication

Grimmjow

[h=2][/h]

I am new to CCNA........I have a host1 192.168.1.2 ( vlan 2) in Switch 0 and host2 192.168.1.9 (vlan 2) in switch 1 . Switch 1 and 0 are connected to switch 2 as a trunk. But ping fails between host1 and host 2 .....host 1 arp should flow to host 2 through switch 2 and switch 1 right.....i am not sure why?? Help needed pls (y)

Jon_Cisco

Just start running through options.

All ports are active.
Ports show up in the correct vlan when you use show commands.
Trunking was successful so you don't see your trunk in a vlan.
No firewall is blocking the ping.
Subnet masks match.

Are you working with a real lab or a simulator?

Grimmjow

I am working in a simulator......trunks are successful as i was able to configure vlans through vtp....I checked the ports and subnet masks match

EdTheLad

Provide some show commands, this is how you shoud be troubleshooting the issue!

On all switches provide the following:

show vlan
show interface trunk
show interface x/x switchport
sho spanning-tree vlan x
shwo mac address-table vlan x

broli720

EdTheLad wrote: »

Provide some show commands, this is how you shoud be troubleshooting the issue!

On all switches provide the following:

show vlan
show interface trunk
show interface x/x switchport
sho spanning-tree vlan x
shwo mac address-table vlan x

As stated above, having this information would narrow down a lot of issues.

Grimmjow

Thank you Ed ......I was assuming spanning tree will be enabled for all vlans by default.....It is enabled only for default vlan although this could be model specific i guess!

Grimmjow

will VTP PRUNING command automatically decide which vlans to negotiate with other switches???

EdTheLad

VTP pruning will remove a vlan from trunk allow list if the downstream switches don't have any active interfaces with the vlan.

EdTheLad

Are you sure the vlan is configured on the switch? as in "show vlan" displays the vlan. Just assigning a vlan to an access port is not always enough, sometimes you have to manually config the vlan. i.e. router(config)#vlan 100
I've seen lots of different behavior over the years in regards to adding vlans, stp etc, so i just check it all as i never remember how the different switches default.

Grimmjow

I used a Catalyst 2950-24 switch.......it does not have an option to prune vtp(i believe this will enable active vlans to span)........so i used Switch(config)#spanning-tree vlan 2......it works fine now ......i created vlan 2 in config mode only, i did not directly access with switchport

EdTheLad

If there is no prune option, it will span all active and inactive vlans across trunks. Now the question is, why was it not working when SPT was disabled on the switches? You have 3 switches connected in series, what was happening? You shouldn't just ping end to end and walk away, you need to dig deeper and understand whats going on, otherwise your wasting your time.