Peter Rathlev wrote: > Hi Jose, > > You need to enable large MTU on the core facing interfaces on both > sides, and on all interfaces on the core routers. The interfaces that > have LDP enabled is no bad guess. > > You can raise the interface MTU with the "mtu X" interface config > command. If you don't specify any "mpls mtu X" command it will follow > the interface MTU. Don't adjust "mpls mtu" unless you have a good > reason. > > You would need 1518 bytes Ethernet + 4 bytes 802.1Q (if that's your > protocol) and 4+ bytes MPLS (depending on how many labels you stack). > I'm not sure the 1811 supports baby giants/jumbo frames, but you can try > at least. I've seen a value of 1546 used often, although I don't know > exactly why. :-) > > Regards, > Peter > > > On Fri, 2008-02-29 at 13:21 -0500, The Father wrote: > >> Hi group. I'm wondering if someone can help me out with a bit of an MTU >> issue I'm seeing when playing around with EoMPLS in our lab. >> >> This is the topology I have setup: >> >> 3550-24------3750-----7603/Sup32-------1811-------7206VXR-NPE300-----3750------3550-24 >> >> >> >> LDP is enabled between the 7600, 1811 and 7200 (yes it's an 1811 as my P >> for now). I have created VLAN 800 on the first 3550 and used the >> xconnect command on the ingress Gig interface of the 7603 (sub-interface >> is used). The circuit is encapsulated and sent over to the 7206VXR >> (sub-interface used here too). From there it is sent over to the other >> 3550 (obviously trunking is being done between the 3550s and 3750s). We >> have also created SVIs on the 3550s to act as our layer 3 interfaces >> with IPs. >> >> When we try and ping from one end to the other with 1500 byte sized >> packets it fails. The highest we can go is 1478. I know that with MPLS >> you normally are required to enable jumbo frame support but where >> exactly would I do this? Is it on the interfaces that have LDP enabled >> on them or in the entire network I have setup above? Currently >> everything is set to the default of 1500. >> >> Another thing that I'm confused about is when to use the "mpls mtu xxx" >> command. If I understand it correctly, you must have the interface MTU >> set higher than the MPLS MTU. I have tried using the "mpls mtu 1520" >> command on the LDP enabled interfaces but it has made no >> difference...probably because the interface MTU is still 1500. >> >> Any thoughts or advice on trying to resolve this? >> >> Thanks. >> >> Jose >> >> _______________________________________________ >> cisco-nsp mailing list [email protected] >> https://puck.nether.net/mailman/listinfo/cisco-nsp >> archive at http://puck.nether.net/pipermail/cisco-nsp/ >> > > > > __________ NOD32 2912 (20080229) Information __________ > > This message was checked by NOD32 antivirus system. > http://www.eset.com > > > > Thanks for the tips Peter. Is "ip mtu xxx" on an interface the same as using "mtu xxx"? Seems like I don't have the ability to change the mtu on some of the linecards of the 7600.
Jose _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
