Routing
Highlighted
Routing

about the routing table "mpls.0"

‎10-19-2011 07:08 AM

what's means about "(S=0)"in the output

 

 


mpls.0: 7 destinations, 7 routes (7 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

0                  *[MPLS/0] 01:37:25, metric 1
                      Receive
1                  *[MPLS/0] 01:37:25, metric 1
                      Receive
2                  *[MPLS/0] 01:37:25, metric 1
                      Receive
300032             *[LDP/9] 00:29:39, metric 1
                    > to 10.0.8.5 via em3.66, Pop     
300032(S=0)        *[LDP/9] 00:29:39, metric 1
                    > to 10.0.8.5 via em3.66, Pop     
300048             *[LDP/9] 00:29:14, metric 1
                    > to 10.0.8.10 via em2.55, Pop     
300048(S=0)        *[LDP/9] 00:29:14, metric 1
                    > to 10.0.8.10 via em2.55, Pop  

 

thanks a lot!

2 REPLIES 2
Highlighted
Routing

Re: about the routing table "mpls.0"

‎10-19-2011 08:25 PM

Check this out

http://www.juniper.net/techpubs/en_US/junos10.0/information-products/topic-collections/nog-mpls-mode... 

 

There are two entries per route because the stack values in the MPLS header may be different. For each route, the second entry 300032 (S=0) and 300048 (S=0) indicates that the stack depth is not 1, and additional label values are included in the packet. In contrast, the first entry, 300032 and 300048 has an inferred S=1 value which indicates a stack depth of 1 and makes each label the last label in that particular packet. The dual entries indicate that this is the penultimate router.

 

HTH

/Fox

Highlighted
Routing

Re: about the routing table "mpls.0"

‎09-13-2019 12:33 AM

"S=0" basically means that the label is not at the bottom at the label stack, and that there are more labels to follow. There are situations when a packet would contain more than 1 label, with each meant to achieve a different objective. In such scenario, we can choose our router to treat such a packet differently, in comparison to packets that have only one label ( "S=1", not shown in the above output, but is implicit for the other routes that do not have "S=0"). This is the reason 2 entries are present in the routing table for the same destination prefix.

 

HTH 

Vishal