The MPLS-OPS Archive[Date Prev][Date Next][Thread Prev][Thread Next] [Date Index][Thread Index][Author Index][Subject Index] Re: [MPLS-OPS] tag-switching mtu command on cisco IOS
> Θ«ΘρΌ® wrote: > > Hi Everyone~~ > > I have a question about cisco's " tag-switching mtu" command. > Please let me know the good answer and reason... > > ----------------------------------------------------------------------------- > (( Diagram )) > > --[IP Network]----(e0/0) "CISCO ROUTER" (e0/1)----[ MPLS Network ]---- > > (( Situation -1 )) > (1) Configuration > - IP datagram mtu on e0/1 = 1500 Byte (Default Configuration) > - "tag-swtiching mtu 1504" on e0/1 interface. > > (2) IP Packet Arrived from e0/0 > -Size : 1500-Byte > -DF Bit Set : No > -Forwarding Interface : e0/1 > -1 Label will be imposed.(4 byte overhead) > > Will the Cisco router fragment this IP packet before sending it to e0/1? No. > or send 1504 Labeled packet without fragmentation. ( override IP mtu 1500 ) > There is no overriding here. IP mtu is only for IP packets not for MPLS packets. If you haven't configured any mpls mtu default value will be same as IP mtu. > (( Situation -2 )) > (1) Same Configuration, Same Diagram to Situation-1 > (2) IP Packet Arrived from e0/0 > -Size : 1500-Byte > -DF Bit Set : No > -Forwarding Interface : e0/1 > -2 Label will be imposed.(8 byte overhead ..) > > Will the Cisco router fragment this IP packet before sending it to e0/1? yes, for the obvious reason that out going tagged packet is more than tag mtu. thanks, Santhosh. > ----------------------------------------------------------------------------- > > Thanks > Best Regards. > > > ================================================== > Huisuk Hong > System Engineering > ================================================== ------- The MPLS-OPS Mailing List Subscribe/Unsubscribe: http://www.mplsrc.com/mplsops.shtml Archive: http://www.mplsrc.com/mpls-ops_archive.shtml
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