MPLS l2 vfi MTU not reached 1500

[NOC_Infonet]

HI all,

I have faced MTU issue in MPLS L2 vfi tunnel. 

End A

l2 vfi VLAN2559 manual
vpn id 2559
bridge-domain 2559
mtu 9180
neighbor 192.168.100.10 encapsulation mpls

interface BDI2559
ip vrf forwarding cisco
ip address 192.168.10.1 255.255.255.252

End-B

l2 vfi VLAN2559 manual
vpn id 2559
bridge-domain 2559
mtu 9180
neighbor 192.168.100.49 encapsulation mpls

interface BDI2559
ip vrf forwarding cisco
ip address 192.168.10.2 255.255.255.252

Router(config)#do ping vrf sify 192.168.10.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.10.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/21/24 ms

Router(config)#do ping vrf sify 192.168.10.1 size 1500
Type escape sequence to abort.
Sending 5, 1500-byte ICMP Echos to 192.168.10.1, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)

Kindly verify the above mention the log What should go wrong? Please help.

[MHM Cisco World]

simple answer your SP is not accept value 1500 you must reduce it with at least 24 bytes (assume there will be three label add to frame). 

[NOC_Infonet]

Please kindly explain briefly. 

[MHM Cisco World]

your SP Core can support only standard Frame which is 1518-1522, 
and you push traffic 1500 before add MPLS labels then the traffic  will drop 
you must reduce the traffic you push to be + MPLS labels less than 1518-1522 value.
command you can use to set the correct value is 
MPLS MTU 
and you can see the MTU use by SP by
show mpls forwarding-table detail 

 

[smilstea]

MTU configured in the BD is just for signalling, you would have to configure MTU on the ACs / physical interfaces for the MTU to change. At least that is the case for XR (the board where this post was posted).

Sam