Cisco ASR 900 Series User Manual

Option Interactions and Loops
Usage examples for the MPLS LSP Ping and Traceroute and AToM VCCV feature in this and subsequent
sections are based on the sample topology shown in the figure below.
Figure 8: Sample Topology for Configuration Examples
The interaction of some MPLS LSP Ping and Traceroute and AToM VCCV options can cause loops. See the
following topic for a description of the loops you might encounter with the ping mpls and trace mpls
commands:
Possible Loops with MPLS LSP Ping
With the MPLS LSP Ping feature, loops can occur if you use the repeat count option, the sweep size range
option, or the User Datagram Protocol (UDP) destination address range option.
ping mpls
{ipv4 destination-address/destination-mask
[destination address-start address-end increment] | pseudowire ipv4-address
vc-id vc-id
[destination address-start address-end increment] |
traffic-eng tunnel-interface tunnel-number}
[repeat count]
[sweep minimum maximum size-increment]
Following is an example of how a loop operates if you use the following keywords and arguments on the ping
mpls command:
Device# ping mpls
ipv4
10.131.159.251/32 destination 127.0.0.1 127.0.0.1 0.0.0.1 repeat 2
sweep 1450 1475 25
Sending 2, [1450..1500]-byte MPLS Echos to 10.131.159.251/32,
timeout is 2 seconds, send interval is 0 msec:
Codes: '!' - success, 'Q' - request not transmitted,
'.' - timeout, 'U' - unreachable,
'R' - downstream router but not target
Type escape sequence to abort.
Destination address 127.0.0.1
!
!
Destination address 127.0.0.1
!
!
Destination address 127.0.0.1
!
!
Destination address 127.0.0.1
!
!
An mpls ping command is sent for each packet size range for each destination address until the end address
is reached. For this example, the loop continues in the same manner until the destination address, 127.0.0.1,
is reached. The sequence continues until the number is reached that you specified with the repeat count
MPLS Basic Configuration Guide, Cisco IOS XE Everest 16.5.1 (Cisco ASR 900 Series)
79
MPLS LSP Ping, Traceroute, and AToM VCCV
Command Options for ping mpls and trace mpls

Cisco ASR 900 Series Specifications

General

Brand	Cisco
Model	ASR 900 Series
Category	Network Router
Language	English