Just wanted to understand the significance of “Bytes Label switched” field present in “sh mpls forwarding-table” cmd’s o/p … what it means, why value is always “0” and can it be non-zero as well, if Yes, when?
show mpls forwarding-table command is used to display the contents of the MPLS label forwarding information base (LFIB). Within the LFIB, there is a column with the heading “Bytes Label Switched” as you state in your post. This value shows the number of bytes switched with this incoming label. The total value includes the size of the outgoing label and the Layer 2 header as well.
If you see values of 0, this means that this particular label is not being used to switch traffic. Note however that traffic will increase this counter only if the traffic is entering the route labeled. If the traffic is entering on the head end of the LSP, that is, from the customer, and it is plain IP traffic, then CEF switches it, and this value will remain zero.
Take a look at the following Cisco documentation that describes the output of this command in more detail.
I hope this has been helpful!