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FAQ-How to View the Actual MPLS MTU Value of the NE40 Node

Publication Date:  2012-07-27 Views:  121 Downloads:  0

Issue Description

After MPLS is enabled on the NE40, both the MTU value of the physical interface and the MPLS MTU value exist. As we know, if the MTU value of any node is not configured by default, this node sends MTU negotiation messages to all LSP nodes passing it through the LDP protocol. The actual MPLS MTU value of each node adopts the smaller one of MPLS MTU configured and interface MTU configured and then compares with the minimum MTU returned by the LSP downstream node passing this node to adopt the smallest value.
How to view the actual MPLS MTU value on the NE40? The MTU value displayed by running the disp mpls interface verbose command is not an enabled and negotiated one, and only the MTU value viewed in the outsegment entry is. Then, by running which command can it be displayed? 

Alarm Information


Handling Process

Do as follows to view the outsegment entry:
[243-diag]display efu fib 4 32
Start display lpu fib on board 04...
Message sending success.
IP address =
IP prefixLength = 32
VRF index = 0
Signature = 0
counterskip = 1
cbi = 0
ecmpThr1 = 100
ecmpThr2 = 0
qppbindex = 0x0
         nextHop[0] lsptoken = 0 Indicates MPLS forwarding
          egressContext = 0
          tb= 5 tp=0x3 subIndex=0 route outbound interface
         nextHop[0] is MPLS
         NextHop[0] OutPortType = 3,
[243-diag]display efu outsegment 4 0 (4 is the slot number and 0 is lsptoken)
Start display lpu outsegment on board 04...
Message sending success.
LSP OutSegment entry query response:
lsp token is 0
protocol is 1
control is 0x19
state is Up
mac valid
qppb is disable
label is 3
queueBase is 0
Queue Index is 0 (BE)
maxQIndex is 0
Mac Addr is 0001-0000-0001
vlan_id field value is 0
next_token field value is 0
TB is : 5
TP is : 3
VCD is : 0
TE card ID is 0
frr protect label is 1048575
frr token is 4294967295
te frr enable is not set
QPPB index is 0x0
MPLS MTU is 1500 ---Obtain the MPLS MTU value
Note: The MTU value displayed by running the disp mpls interface verbose command is not an enabled and negotiated one and that viewed in the outsegment table is. 

Root Cause