High Latency in 'trace mpls ipv4'

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Aug 10th, 2008
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Seeing higher latecny when doing trace mpls ipv4; is there a valid reason for that?


PE1#trace 10.10.10.128


Type escape sequence to abort.

Tracing the route to 10.10.10.128


1 10.10.129.94 [MPLS: Label 297 Exp 0] 4 msec

10.10.129.90 [MPLS: Label 297 Exp 0] 8 msec

10.10.129.94 [MPLS: Label 297 Exp 0] 8 msec

2 10.10.128.53 [MPLS: Label 225 Exp 0] 4 msec 4 msec 8 msec

3 10.10.128.49 [MPLS: Label 34 Exp 0] 8 msec 4 msec 8 msec

4 10.10.129.5 8 msec * 4 msec


While same trace with trace mpls ipv4 option shows higher latencies:


PE1#trace mpls ipv4 10.10.10.128/32

Tracing MPLS Label Switched Path to 10.10.10.128/32, timeout is 2 seconds


Codes: '!' - success, 'Q' - request not sent, '.' - timeout,

'L' - labeled output interface, 'B' - unlabeled output interface,

'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,

'M' - malformed request, 'm' - unsupported tlvs, 'N' - no label entry,

'P' - no rx intf label prot, 'p' - premature termination of LSP,

'R' - transit router, 'I' - unknown upstream index,

'X' - unknown return code, 'x' - return code 0


Type escape sequence to abort.

0 10.10.129.89 MRU 1538 [Labels: 297 Exp: 0]

L 1 10.10.129.90 MRU 4470 [Labels: 225 Exp: 0] 252 ms

I 2 10.10.128.53 MRU 4470 [Labels: 34 Exp: 0] 688 ms

I 3 10.10.128.49 MRU 1604 [Labels: implicit-null Exp: 0] 1000 ms

D 4 10.10.129.5 8 ms

! 5 10.10.129.5 4 ms


Ping mpls shows normal though:


PE1#ping mpls ipv4 10.10.10.128/32

Sending 5, 100-byte MPLS Echos to 10.10.10.128/32,

timeout is 2 seconds, send interval is 0 msec:


Codes: '!' - success, 'Q' - request not sent, '.' - timeout,

'L' - labeled output interface, 'B' - unlabeled output interface,

'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,

'M' - malformed request, 'm' - unsupported tlvs, 'N' - no label entry,

'P' - no rx intf label prot, 'p' - premature termination of LSP,

'R' - transit router, 'I' - unknown upstream index,

'X' - unknown return code, 'x' - return code 0


Type escape sequence to abort.

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 4/5/8 ms

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smahbub Thu, 08/14/2008 - 10:44
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To discover Multiprotocol Label Switching (MPLS) label switched path (LSP) routes that packets actually take when traveling to their destinations, use the trace mpls command in privileged EXEC mode. High latency while using trace mpls ipv4 does not have any effect on the device.


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