Need to allow VLAN at specific link

[Mahmoud Marie]

Hello,

I have two PCs connected to the same switch and there are two uplinks to another switch as the below diagram, just need to know how to let VLAN 40 going through "Dark-Fiber-1" Port1 and VLAN30 going through "Dark-Fiber-2" Port-5

Appreciate you help

Thanks

[MHM Cisco World]

https://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/10555-15.html

MHM

[Mahmoud Marie]

They not a redundant links, its a separated links. Just need to allow VLANs at each link.

Link-1 for VLAN-40 traffic only and Link-2 for VLAN-30 only

Thanks

[MHM Cisco World]

If that so 

Config each port as access 

And assign vlan to port.

Note:- this work if you run pvst not rstp'

So what STP mode you run in SW?

MHM

[MHM Cisco World]

this lab for you

the port config with 

swithport access vlan 10/100 
and both SW run PVST or (rapid-PVST)

and it work the VLAN1 since it run by default in both link one side is BLK and other is FWD 
and for VLAN 10/100 the port is FWD 

[Mahmoud Marie]

Thank you @MHM Cisco World 

The spanning tree mode "rstp" on each switch. 

IF I configure the port to switch access that will allow one vlan, so If I need to adding one more vlan later that will not possible.

So There is anyway to let the two links working with trunk mode and allow some VLANs for each link.

example: Link-1 carry traffic for VLAN 40 & 20

Link-2 carry traffic for VLAN 30 & 10 

Thanks

[balaji.bandi]

IF I configure the port to switch access that will allow one vlan, so If I need to adding one more vlan later that will not possible.

you can add and delete VLAN when and then required, i do not see any issue.

example: Link-1 carry traffic for VLAN 40 & 20

Link-2 carry traffic for VLAN 30 & 10 

yes this possible if both the side have same configuration.

For redundancy you can also add all the VLAN in both the Trunk with Priority of STP each link for the respected VLAN.

In case one of the Links failed, other link still pass traffic for all VLAN - example  as per your requirement.

More information can be find here : (let us know if you looking any example) 

https://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/10556-16.html

[Joseph W. Doherty]

"The spanning tree mode "rstp" on each switch."

On Cisco switches, correct?  If so . . .

'So There is anyway to let the two links working with trunk mode and allow some VLANs for each link."

Yes there is.  You define what VLANs are allowed to transverse the trunk.

But, if this was for real, there are a couple of better ways to use those two links.

First, you could LACP the dual links into one logical link.  This would also support standard (non-Cisco) STP and rapid-STP.

Second, with Cisco, you can prefer one link over another for each VLAN.

Both of the forgoing would keep all VLANs in operation even if either link goes down.

[MHM Cisco World]

Please make double check when you do

Show spanning tree 

Do you see one root or many root (one root for each vlan)?

Why I ask' cisco SW something refers to rapid pvst abd rstp' so I need to know exactly stp mode

MHM

[Joseph W. Doherty]

---

@MHM Cisco World wrote:

If that so 

Config each port as access 

And assign vlan to port.

Yep, that should do it.

---

@MHM Cisco World wrote:

If that so 

Note:- this work if you run pvst not rstp'

So what STP mode you run in SW?

---

Eh?

I believe what @MHM Cisco World is trying to say, i.e. there's no issue with Cisco's per-VLAN STP implementation but there is with rapid-STP.  But, as worded in the above, although that's correct, it's possibly unclear, as he contrasts Cisco's STP (pvst) with rapid-STP it might be thought there's an issue between non-rapid vs. rapid..  The looping issue is using standard (non-Cisco) STP or rapid-STP.  Not an issue for Cisco's pvst or rapid-pvst (the latter is explicit in his lab reply).

[paul driver]

Hello

---

@Joseph W. Doherty wrote:.
there's no issue with Cisco's per-VLAN STP implementation but there is with rapid-STP.  

@MHM Cisco World  What is that, can you elaborate ?

[Joseph W. Doherty]

Dang!  @paul driver my reply you're quoting from was intended to clarify what I believe he meant.  (As he gave me a helpful vote on that reply, I presume I succeeded.)

Basically OP didn't specifically note Cisco switches were being used, and so for the topology being used, dual links might form a L2 loop.

@MHM Cisco World was (correctly) noting a link for each VLAN would only work with a per VLAN STP variant, like Cisco's.

[paul driver]

Hello

Allow BOTH vlan to traverse each trunk and then
set the port -priority for the less preferred vlan to be advertised to the neighbour switch

l2 switch(s) Sw1-Sw2

int <dark fibre1)
spanning-tree vlan 30 port-priority 200

int <dark fibre2)
spanning-tree vlan 40 port-priority 200

[Mahmoud Marie]

If I create direct connection between the Layer-2 switch and CS-1 & CS-2 as the below diagram:

How to allow VLAN10 & VLAN20 only from Link-1 and VLAN30, VLAN40, VLAN50 only from Link-2

Thanks 

[MHM Cisco World]

if there is no interconnect between CS-1 and CS-2 then 

simple 
config link1 as trunk and allow vlan 10,20 

config link2 as trunk and allow vlan 30,40,50

MHM