VTP Pruning

[parthrawat979]

Can someone help me understand the concep of vtp pruning.
In my topology SW1 is the server and the rest are clients. Vlans configured are 10,20,30,40
So as far as I know if vtp pruning is enabled and  a device in vlan 10 ping to another device on vlan 10 in my topology(vpc 5 ping to vpc 7) the arp(broadcast) should never reach Sw4 because it doesn't have any ports bind to vlan 10. But in the capture I found out that the arp is reaching till SW4?? Why's that happening??

This is the output of trunk interface on Sw4

Port Vlans allowed on trunk
Et0/0 1-4094

Port Vlans allowed and active in management domain
Et0/0 1,10,20,30,40

Port Vlans in spanning tree forwarding state and not pruned
Et0/0 1,10,20,30,40
&&
this is on sw3 
Port Vlans in spanning tree forwarding state and not pruned
Et0/0 1,10,20
Et0/1 1,30,40
so if sw3 int e0/1(interface toward sw4) only sends traffic of vl 1,30,40 so why am I getting an arp request with a tag of vlan 10.

[paul driver]

Hello
The 3750s you could debug vtp not so sure on the cat9ks but you could try:
example:
debug sw-vlan vtp

[Joseph W. Doherty]

So what you're seeing is unexpected, it's software bug which happens almost always with the virtual switch models you're testing.

BTW, I agree, from the VTP pruning stats, a V10 ping from SW1 shouldn't reach SW4.

On Switch 1:

Port Vlans in spanning tree forwarding state and not pruned
Et0/0 1,10,20,30,40

On Switch 2:

Port Vlans in spanning tree forwarding state and not pruned
Et0/0 1,10,20
Et0/1 1,30,40

On SW3:

Port Vlans in spanning tree forwarding state and not pruned
Et0/0 1,10,20
Et0/1 1,30,40

Switch 4

Port Vlans in spanning tree forwarding state and not pruned
Et0/0 1,10,20,30,40

According to the above, SW2, STP should be blocking VLANs 10 and 20 to SW3.

[paul driver]

Hello
change vtp version - to 2
test again 

[Cristian Matei]

Hi,

   It's not a VTP version issue here, just well known issue / bug regarding virtual non CAT 9k images.

Thanks,

Cristian.

[paul driver]

hello
not aware of the bug - my suggestion is based on eve-ng labs also and accidentally coming cross this type of issue upon noticing pruning active for the vtp domain- 

enabling v2 seem to resolve the dynamic pruning issue highlighted by the OP

TBH I always try manual prune all TRKs where applicable if when running vtp excluding when running 802.1S then  i would say its unnecessary to prune TRKs 

[parthrawat979]

V2 changes nothing.

[Joseph W. Doherty]

It's not a VTP version issue here, just well known issue / bug regarding virtual non CAT 9k images.

I cannot comment on the accuracy of such a statement, but I can say providing an emulator is loaded with issues, especially regarding performance, which, alone can cause bugs to arise.

Switches, in particular, usually have additional hardware, some of which, may be proprietary, i.e. what it can do, and how to invoke such features, is not public information.  (Which is why something like CML is less likely to have issues.)

Above, I note an emulation's lack of performance may reveal bugs.  This because, when you get to parts of software that directly works the hardware, there may be some timing bugs, that, on existing hardware, have not been triggered.  Running such software on a different platform, such as an emulator, might trigger them.  BTW, this issue isn't limited to just emulators, running the same software on a "like" hardware platform, running at a different performance level, might trigger them too.  (Ever notice, sometime, a newer, usually "faster" platform, added to a series, might initially have some issues running the "same" IOS version?  [For any into PC "overclocking", although running too fast failures are usually due to hardware literally stops working correctly beyond some rate, some failures might also be due to timing bugs ])