Mpls Lsp Tracert; Configuring Bfd For Lsps - H3C SR8800 10G Mpls Configuration Manual

Task
Use MPLS LSP ping to check the
connectivity of an MPLS LSP.

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 specific value. Then, each hop along the LSP will return
an MPLS echo reply to the ingress due to TTL timeout. Thus, 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.
To locate errors of an LSP:
Task
Perform MPLS LSP tracert to locate
an MPLS LSP error.

Configuring BFD for LSPs

You can configure BFD for an LSP to detect the connectivity of the LSP. After the configuration, a BFD
session will be established between the ingress and egress of the LSP, and the ingress will add the label
for the FEC to into a BFD control packet, forward the BFD control packet along the LSP to the egress, and
determine the status of the LSP according to the reply received. Upon detecting an LSP failure, BFD
triggers a traffic switchover.
A BFD session for LSP connectivity detection can be static or dynamic.
Static: If you specify the local and remote discriminator values by using the discriminator keyword
•
when configuring the bfd enable command, the BFD session will be established with the specified
discriminator values. Such a BFD session is used to detect the connectivity of a pair of LSPs in
opposite directions (one from local to remote, and the other from remote to local) between two
routers.
Dynamic: If you do not specify the local and remote discriminator values when configuring the bfd
•
enable command, the MPLS LSP ping will be run automatically to negotiate the discriminator values
and then the BFD session will be established based on the negotiated discriminator values. Such a
BFD session is used for connectivity detection of an LSP from the local router to the remote router.
Configuration prerequistes
The BFD session parameters are those configured on the loopback interface whose IP address is
•
configured as the MPLS LSR ID, and the BFD packets will use the MPLS LSR ID as the source address.
Therefore, before enabling BFD for an LSP, you need to configure an IP address for the loopback
interface and configure the IP address as the MPLS LSR ID. You can also configure BFD session
Command
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 ]
Command
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 ]
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