H3C Technologies H3C S10500 Series Switches - Manual (Page 82)

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Inspecting LSPs
In MPLS, the MPLS control plane is responsible for establishing LSPs. However, when an LSP fails to
forward data, the control plane cannot detect the LSP failure or cannot do so in time. This makes network
maintenance difficult. To find LSP failures in time and locate the failed node, the device provides the
following mechanisms:
• MPLS LSP ping
• MPLS LSP tracert
• BFD for LSPs
• Periodic LSP tracert
Configuring MPLS LSP ping
MPLS LSP ping is for checking the connectivity of an LSP. At the ingress, it adds the label for the FEC to
be inspected into an MPLS echo request, which then is forwarded along the LSP to the egress. The egress
processes the request packet and returns an MPLS echo reply to the ingress. An MPLS echo reply carrying
a success notification indicates that the lSP is normal, and an MPLS echo reply carrying an error code
indicates that the LSP has failed.
Use the following command to check the connectivity of an LSP:
To do… Use the command… Remarks
Use MPLS LSP ping to check MPLS
LSP connectivity
ping lsp [ -a source-ip | -c count |
-exp exp-value | -h ttl-value | -m
wait-time | -r reply-mode | -s
packet-size | -t time-out | -v ] *
ipv4 dest-addr mask-length
[ destination-ip-addr-header ]
Required
Available in any view
Configuring MPLS LSP tracert
MPLS LSP tracert is for locating LSP errors. It consecutively sends the MPLS echo requests along the LSP to
be inspected, with the TTL increasing from 1 to a specified value. Then, each hop along the LSP will return
an MPLS echo reply to the ingress due to TTL timeout. So, the ingress can collect the information of each
hop along the LSP, so as to locate the failed node. You can also use MPLS LSP tracert to collect the
important information of each hop along the LSP, such as the label allocated.
Use the following command to locate errors of an LSP:
To do… Use the command… Remarks
Perform MPLS LSP tracert to locate
errors along an MPLS LSP
tracert lsp [ -a source-ip | -exp
exp-value | -h ttl-value | -r
reply-mode |-t time-out ] * ipv4
dest-addr mask-length
[ destination-ip-addr-header ]
Required
Available in any view
Configuring BFD for LSPs
You can configure BFD to detect the connectivity of an LSP. After the configuration, a BFD session is
established between the ingress and egress of the LSP, and the ingress will add the label for the FEC into