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Need to understand output of "Traceroute mpls ldp"

‎10-15-2017 07:35 AM

Hello Experts,

I have created a topology consisting of 4 routers, i'm using ospf as in IGP for connectivity and have enabled mpls and ldp on all the interfaces  required,Here is the topology overview re

R1<------------------>R2<--------------->R3<-------------->R4

 

i'm recevied routes for R1 loopback interface on R4 in inet.0 & inet.3 table, but when i'm tracing to R1 loopback address i'm not able to see label details

here is the output from R4 router

=======================

R4

show route table inet.0

inet.0: 16 destinations, 16 routes (16 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

1.1.1.0/24 *[OSPF/10] 00:32:45, metric 4
> to 10.10.45.4 via em1.0
1.1.1.1/32 *[OSPF/10] 00:32:45, metric 4

===============

show route table inet.3

inet.3: 4 destinations, 4 routes (4 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

1.1.1.1/32 *[LDP/9] 00:24:02, metric 1
> to 10.10.45.4 via em1.0, Push 299808

==================

traceroute mpls ldp 1.1.1.1
Probe options: ttl 64, retries 3, wait 10, paths 16, exp 7, fanout 16

ttl Label Protocol Address Previous Hop Probe Status
1 299808 LDP 10.10.45.4 (null) Unhelpful
2 4.4.4.4 10.10.45.4 Unhelpful
3 4.4.4.4 4.4.4.4 Unhelpful

Snipped output

62 4.4.4.4 4.4.4.4 Unhelpful
63 4.4.4.4 4.4.4.4 Unhelpful
64 4.4.4.4 4.4.4.4 Unhelpful
65 (null) 4.4.4.4 TTL expired

Unexplored path via em1.0 destination 127.0.0.64

7 REPLIES 7
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Re: Need to understand output of "Traceroute mpls ldp"

‎10-15-2017 10:07 AM

Hi shani,

 

Check it matches KB25210.

Also, Can you attach the configuration from all the routers and what is the junos version you are running on lab

 

 

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Re: Need to understand output of "Traceroute mpls ldp"

‎10-16-2017 04:48 AM

Hello vvadivel,

 

I have checked regarding KB25210 on Internet but not able to find any relevant details about it.

Could you please help me in details with KB25210.

Here i'm attaching the configuration and version details of my lab setup.

Thanks.

 

Attachments

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Re: Need to understand output of "Traceroute mpls ldp"

‎10-16-2017 08:55 AM

Hi Shani,

 

An unhelpful node is one that returns an echo reply, which has no downstream mapping TLVs. The Router, when responding to the traceroute, does not provide the  next-hop address in the traceroute reply. Instead, it just returns 127.0.0.1. So, the Unhelpful state is generated.


   15:46:03.266288 Out MPLS (label 299840, exp 6, [S], ttl 64)
        IP (tos 0xc0, ttl  64, id 10072, offset 0, flags [none], proto: UDP (17), length: 60) 22.22.22.22.lsp-ping > 11.11.11.11.58557:
        LSP-PINGv1, flags [0x0], msg-type: MPLS Echo Reply (2), length: 32
          reply-mode: Reply via an IPv4/IPv6 UDP packet (2)
          Return Code: Upstream Interface Index Unknown (6)
          Return Subcode: (1)
          Sender Handle: 0xb0000000, Sequence: 2

   
15:46:58.137069 Out IP (tos 0xc0, ttl  64, id 8300, offset 0, flags [none], proto: UDP (17), length: 60) 33.33.33.33.3503 > 11.11.11.11.52519:
        LSP-PINGv1, flags [0x0], msg-type: MPLS Echo Reply (2), length: 32
          reply-mode: Reply via an IPv4/IPv6 UDP packet (2)
          Return Code: Label switched at stack-depth 1 (8)
          Return Subcode: (1)
          Sender Handle: 0xb0000000, Sequence: 1

   
15:53:19.570988 Out MPLS (label 299968, exp 6, [S], ttl 64)
        IP (tos 0xc0, ttl  64, id 9980, offset 0, flags [none], proto: UDP (17), length: 60) 44.44.44.44.lsp-ping > 11.11.11.11.65100:
        LSP-PINGv1, flags [0x0], msg-type: MPLS Echo Reply (2), length: 32
          reply-mode: Reply via an IPv4/IPv6 UDP packet (2)
          Return Code: Replying router is an egress for the FEC at stack depth 1 (3)
          Return Subcode: (1)
          Sender Handle: 0xb0000000, Sequence: 5

   
   
root@R2# run traceroute mpls ldp 44.44.44.44 source 11.11.11.11          
  Probe options: ttl 64, retries 3, wait 10, paths 16, exp 7, fanout 16
                 source 11.11.11.11

  ttl    Label  Protocol    Address          Previous Hop     Probe Status
    1   299888  LDP         20.20.20.2       (null)           Unhelpful        
    2                       22.22.22.22      20.20.20.2       Unhelpful        
    3                       44.44.44.44      22.22.22.22      Egress           

  Path 1 via ge-0/0/2.0 destination 127.0.0.64


[edit]
root@R2# run traceroute 44.44.44.44                                      
traceroute to 44.44.44.44 (44.44.44.44), 30 hops max, 40 byte packets
 1  20.20.20.2 (20.20.20.2)  12.757 ms  18.733 ms  20.116 ms
     MPLS Label=299888 CoS=0 TTL=1 S=1
 2  30.30.30.2 (30.30.30.2)  29.929 ms  29.588 ms  30.327 ms
     MPLS Label=299936 CoS=0 TTL=1 S=1
 3  44.44.44.44 (44.44.44.44)  30.328 ms  29.607 ms  40.282 ms

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Re: Need to understand output of "Traceroute mpls ldp"

‎10-16-2017 09:44 AM

Thanks for the clarification, so just need to understand as per my configuration when i simple traceroute the ip 4.4.4.4 mpls labels does not appear in the traceroute, is it a normal behaviour?

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Re: Need to understand output of "Traceroute mpls ldp"

‎10-16-2017 09:59 AM

Hi Shani,

 

You can enable mpls-forwarding knob for the same.

 

root@R2# show protocols
mpls {
traffic-engineering mpls-forwarding;
traceoptions {
file oam.log size 10m;
flag lsping;
}
interface ge-0/0/2.0;
interface all;

 

For Unhelpful Probe you can enable log and verify.

 

root@R4# !Oct 16 16:53:51.696418 lsping echo request, from 11.11.11.11, port 16359, src_ifl_idx 73, dest 127.0.0.64, version no 1, seq no 2, tlv type 1 flags 0x0
Oct 16 16:53:51.696494 lsping recv pkt tag[0]: label 300016 exp_bits 0 s_bit 1 ttl 1
Oct 16 16:53:51.921446 lsping dwn mapping rsp from pfe returned 0 nexthops

Oct 16 16:53:51.921499 lsping sent echo reply for seq 2 to 11.11.11.11 from 22.22.22.22 return code Upstream interface index unknown

 

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Re: Need to understand output of "Traceroute mpls ldp"

‎10-17-2017 02:45 AM

Adding the link for KB25210 for reference.  This does require a login to the Juniper support site to view.  

 

https://kb.juniper.net/InfoCenter/index?page=content&id=KB25210

Steve Puluka BSEET - Juniper Ambassador
IP Architect - DQE Communications Pittsburgh, PA (Metro Ethernet & ISP)
http://puluka.com/home
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Re: Need to understand output of "Traceroute mpls ldp"

‎03-23-2019 08:43 AM

before applying  traffic-engineering mpls-forwarding

mpls traceroute first hop not showing label

but after apply traffic-engineering mpls-forwarding     now showing first hop label

 

**Before

root@R11-JMx# run traceroute 10.100.101.5 source 10.100.103.11 
traceroute to 10.100.101.5 (10.100.101.5) from 10.100.103.11, 30 hops max, 40 byte packets
1 10.10.116.6 (10.10.116.6) 11.930 ms 6.177 ms 9.296 ms
2 10.10.36.3 (10.10.36.3) 27.645 ms 32.608 ms 17.462 ms
MPLS Label=19 CoS=0 TTL=1 S=1
3 10.10.13.1 (10.10.13.1) 26.591 ms 35.314 ms 37.598 ms
MPLS Label=16 CoS=0 TTL=1 S=1
4 10.10.15.5 (10.10.15.5) 27.500 ms 28.141 ms 27.306 ms

 

** After

root@R11-JMx> traceroute 10.100.101.5 source 10.100.103.11 
traceroute to 10.100.101.5 (10.100.101.5) from 10.100.103.11, 30 hops max, 40 byte packets
1 10.10.116.6 (10.10.116.6) 41.787 ms 25.197 ms 35.794 ms
MPLS Label=21 CoS=0 TTL=1 S=1
2 10.10.36.3 (10.10.36.3) 39.321 ms 32.600 ms 38.718 ms
MPLS Label=19 CoS=0 TTL=1 S=1
3 10.10.13.1 (10.10.13.1) 34.778 ms 36.035 ms 37.342 ms
MPLS Label=16 CoS=0 TTL=1 S=1
4 10.10.15.5 (10.10.15.5) 37.759 ms 36.426 ms 37.980 ms