Hi Experts, I am testing the MTU size that BDI can support. Please take a look at my config and test below. I configured the physical interface and BDI with MTU 9190. When I do a traceroute mpls, it shows MRU 1500 suggesting that the network interfaces (BDI) can accept packets up to 1500 bytes in size without requiring fragmentation. When I ping the neighbor including the size and df, I can send up to 6354. The neighbor device is also set with MTU 9190. Can you tell me why the traceroute says 1500 MRU but I can send up to 6543? I appreciate the response. TEST-PE#show running-config interface BDI15Building configuration...Current configuration : 277 bytes!interface BDI15ip address 172.22.224.182 255.255.255.252ip mtu 9190ip ospf network point-to-pointip ospf 1 area 0.0.0.0mpls traffic-eng tunnelsbfd interval 300 min_rx 300 multiplier 3ip rsvp signalling hello bfdTEST-PE#show running-config interface gigabitEthernet 0/0/4Building configuration...Current configuration : 266 bytes!interface GigabitEthernet0/0/4mtu 9190no ip addressnegotiation autoservice instance 15 ethernetencapsulation dot1q 15rewrite ingress tag pop 1 symmetricbridge-domain 15!endTEST-PE#show ip interface BDI15BDI15 is up, line protocol is upInternet address is 172.22.224.182/30Broadcast address is 255.255.255.255Address determined by non-volatile memoryMTU is 9190 bytesHelper address is not setDirected broadcast forwarding is disabledTEST-PE#traceroute mpls ipv4 172.22.239.45/32Tracing MPLS Label Switched Path to 172.22.239.45/32, timeout is 2 secondsCodes: '!' - success, 'Q' - request not sent, '.' - timeout,'L' - labeled output interface, 'B' - unlabeled output interface,'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,'M' - malformed request, 'm' - unsupported tlvs, 'N' - no label entry,'P' - no rx intf label prot, 'p' - premature termination of LSP,'R' - transit router, 'I' - unknown upstream index,'l' - Label switched with FEC change, 'd' - see DDMAP for return code,'X' - unknown return code, 'x' - return code 0Type escape sequence to abort.0 172.22.224.182 MRU 1500 [Labels: 393/implicit-null Exp: 0/0]L 1 172.22.224.181 MRU 9190 [Labels: 612 Exp: 0] 44 msL 2 172.22.224.217 MRU 9190 [Labels: 959 Exp: 0] 14 msL 3 172.22.224.194 MRU 9190 [Labels: 2178 Exp: 0] 13 msL 4 172.22.224.141 MRU 9190 [Labels: implicit-null Exp: 0] 19 ms! 5 172.22.224.81 14 msTEST-PE#ping 172.22.224.181 size 6354 dfType escape sequence to abort.Sending 5, 6354-byte ICMP Echos to 172.22.224.181, timeout is 2 seconds:Packet sent with the DF bit set!!!!!Success rate is 100 percent (5/5), round-trip min/avg/max = 8/17/44 msTEST-PE#ping 172.22.224.181 size 6355 dfType escape sequence to abort.Sending 5, 6355-byte ICMP Echos to 172.22.224.181, timeout is 2 seconds:Packet sent with the DF bit set.....Success rate is 0 percent (0/5)TEST-PE#!
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