0

In the penultimate LSR there are following two entries for label 301040:

root@r2> show route table mpls.0 protocol rsvp

mpls.0: 14 destinations, 14 routes (14 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

301040             *[RSVP/7/1] 00:06:53, metric 1
                    > to 172.22.201.14 via ge-0/0/2.0, label-switched-path r1->r4
301040(S=0)        *[RSVP/7/1] 00:06:53, metric 1
                    > to 172.22.201.14 via ge-0/0/2.0, label-switched-path r1->r4

root@r2>

Am I correct, that one should look the S=0 as a condition, i.e if the S=0(bottom of stack bit in MPLS header is not set) then do something and this something can be different when the S=1(bottom of stack bit in MPLS header is set)? For example, LSR could swap the label 301040 with label 12345 if it is at the bottom of the stack or pop the label 301040 if it is not at the bottom of the stack.

1
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can post and accept your own answer.
    – Ron Maupin
    Dec 17 '20 at 19:36
1

S=0 means that the label is not at the bottom at the stack. In some situations, a packet may contain more than 1 label, and each of these labels serves a different purpose. In this case, we can force the router to process such a packet differently than a packet with only one label. Please refer to this(label stacking section): https://www.juniper.net/documentation/en_US/junos/topics/reference/command-summary/show-route-table.html

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.