This document explains how to create virtual tributary (VT) for both
unidirectional path switched ring (UPSR) and bidirectional line switched ring
(BLSR) topologies that run Cisco ONS 15454 Release 3.10 software (Release
the 15454 XC and XC-VT Switching Matrix for an explanation and examples
of the VT matrix capabilities.
Cisco ONS 15454 Troubleshooting and Maintenance Guide contains detailed
specifications of the cross connect (XC), cross connect virtual tributary
(XCVT), and XC10G cards.
You can provision circuits before cards are installed. The ONS 15454
allows you to provision slots and circuits before you install the traffic
cards. Right-click it and choose a card from the shortcut menu in order to
provision an empty slot. But, circuits do not carry traffic until you install
the cards and put their ports into service. Refer to the instructions on how to
install optical, electrical, and Ethernet cards and enabling ports in the
Provisioning document for procedures.
After cards are installed, the ports are out of service. You must place
the ports in service before the circuits carry traffic. Once cards are
installed, and their ports are in service, the circuits carry traffic as soon
as the signal is received.
The information in this document is based on Cisco ONS 15454 Release
3.10 software (Release 3.10-001K-17.01).
The information presented in this document was created from devices in
a specific lab environment. All of the devices used in this document started
with a cleared (default) configuration. If you are working in a live network,
ensure that you understand the potential impact of any command before using
Technical Tips Conventions for more information on document
Note: If you are concerned about consistent bandwidth management, it is
recommended you create two VTT tunnels manually in order to allow the tunnels
to transverse each node and maximize the VT matrix in each node.
In this example, you start with a four-node UPSR with a tunnel created
from nodes B to D.
Under Circuits, create and name your circuit and then choose
Type. In this case, it is a VT tunnel. Click
Choose the source node and then the destination node.
In this example, you can see that the VTT from source node B goes
to destination node D.
At this point you have the option to either route automatically or
uncheck the box in order to route manually. In this example, you route
automatically. Click Finish in order to continue.
When the circuit has been created you can see it in the circuits
At this point, you also get a UNEQ-P alarm on your optical carrier
In this example, you use OC48 cards. These alarms clear once a live
signal is on the tunnel.
Right-click on the span lines in your network view, and choose
Circuits in order to see the tunnel and on which Synchronous
Transport Signal (STS) it rides.
In this case, it is STS 1.
If you highlight the VTT in the circuits list, then choose
Edit and check detailed map, you can see
precisely what the circuit path is.
The second tunnel is created manually. The second tunnel needs to be
created on the same STS, around the opposite side of the ring. The only way to
do this is to route it manually. If you allow the system to route your second
tunnel automatically, it puts it on the next sequential STS. If that happens
and you create your VTs automatically, then you get working and protection
paths on different STSs.
Create the second tunnel automatically in order to see this in action.
Once you create it, you can see it in the circuits list.
Right-click on the span line and choose Circuits
in order to see on which STS the second tunnel rides.
Complete the steps in this procedure:
Repeat the instructions in step 2,
but this time uncheck the Route Automatically box and click
Next in order to create tunnels manually.
Choose the source node in order to change the span lines to arrows.
Once you choose a direction, the line turns white. Click on
Once you add the span, it turns blue and designates the next span
Click on the next span and add it.
At this point, you see that the tunnel is added to the circuit
list. Right-click on the span line in network view and check the STS the tunnel
is in. Choose the STS before you add the span in order to proceed to the
protect side tunnel and ensure that it is created on the same STS around the
opposite side ring. This way you are sure to get the same STS in order to
handle each tunnel.
You are now ready to create your VT1.5 in order to fill up all 28
VTs in the tunnel. Go to circuits and create a VT.
Note: If your tunnels are on different STSs then you get one path in
one tunnel and the second path continues on the same STS. But, this might not
be in a tunnel, which defeats the purpose of the use of a tunnel in order to
Note: Refer to the
and Tunnels chapter of the Cisco ONS 15454 Installation and
Complete the steps in this procedure in order to create VT circuits
You can see here that you go from B/s3/S1/V1-1 to D/s13/S1/V1-1.
Once you have a source and destination, click Next. Double
check in order to ensure the circuit path is correct and click
At this point a message appears and asks if you want to create VT
tunnels on transit nodes. Click No in order to make the VT go
into an existing tunnel.
Once the circuit has been created, right-click on the span line and
see in which tunnel the VT rides.
You see in this example that VTC_B::26 is in TUN_B::24. STS1.
When you look at the other direction of the span line you can also
check to see which tunnel and which STS are used.
You see in this example that VTC_B::26 is also on STS1.
If you chose Yes in step 2 when you got this message,
this is what can happen.
The system automatically creates a new VTT and places VT1.5 into that
If you right-click on the spans, you can see where the VT is placed.
In this case a new tunnel TUN_B::28 is created, and VTC_B::29 is placed
inside the tunnel.
Note: Do not click on Yes in order to create a new tunnel, because there is
no need for it until you fill up the two tunnels that exist.
You can also create VTs manually, place them inside the tunnels, and
choose the STSs on which you want the protect and working to be.
Choose Circuits > Create > VT in order to
start this procedure, then choose your source and destination along with ports,
and uncheck the Route Automatically box.
A message appears and asks if you want to create Transit VTT. Click
No and be prepared to choose tunnels.
Choose the source node and click on it in order to turn the
available span lines into arrows.
The two arrows that point from node B to D represent your tunnels.
Choose one of the arrows. This is your working tunnel path. Click Add
Choose the other arrow. This is your protect path of the VT.
Once the circuit is created it shows up in the circuit list as
Right-click on the span in order to get circuit information in
order to verify that you chose the correct STS.
Note: In order to groom your VTs and VTTs in a UPSR topology, the best
and most recommended way is to create your VTT manually on the same STS and
then place your VTs inside the tunnels. You can create them automatically or
When you create a VTT in a BLSR configuration, it is only necessary to
create one tunnel because the protect path is inherited. You can also use the
route automatically feature with BLSR or manually route.
In this example you create a tunnel from B to D
Choose Circuits > Create and choose VT
tunnel, then click on Next.
In BLSR, you can route the tunnels automatically because the
system only creates circuits on STSs that are fully available throughout the
nodes you go through. Click Next.
If you choose Review Route Before Creation, you
get a visual of which path the circuit plans to take, and you can modify it at
Click Finish in order to add the circuit to the
Right-click on the span in Network view in order to display the
circuits so you can verify that the tunnel is there.
Note: If you choose to create your tunnel manually, the only difference
is to uncheck the Route Automatically box, and proceed as in
the previous steps.
Complete these steps in order to automatically add your VT to the
Under Circuits > Create, choose
VT and choose the slot and port of your source and destination
nodes. In this example, you go from B/s3/S1/V1-1 to D/s13/S1/V1-1. Click
Click Finish if you are ready to proceed with the
Check the circuit list as well as the spans in Network view in
order to see where the circuit is.
Note: If you choose Route Automatically, it goes to
place the VT in the first sequential STS that has room for it. Once it fills up
the STS, the system moves on to the next STS tunnel that has enough room for
Right-click on the Network view span line in order
to see where the circuit is.
Create the VT manually in order to place the VT inside a tunnel and
choose the spans of your choice.
If you choose a span that is not on the same timeslot you get an
Create a VT first in order to also create VTT.
When the system asks you if you want it to create a VTT on transit
nodes, click Yes in order to create a VTT and place the VT
Look at the circuits list in order to verify your
Alternatively, right-click on the span line in network view and
look at the circuits.
If you click No at this point, it adds the VT
without a tunnel.