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Mike, On 08/10/2011 01:54 PM, Mike Horwath wrote: > On Wed, Aug 10, 2011 at 12:33:31PM -0500, Steve Howard wrote: >> Justin, >> >> The CNS MICE switch MTU is configured at 1998/9198. >> >> Steve >> >> >> mice2#show system mtu >> >> System MTU size is 1998 bytes >> System Jumbo MTU size is 9198 bytes >> Routing MTU size is 1998 bytes > I have a quick question.. > > Why would you change this? > > I am hoping I am mising some Internet sekret. > > For our VMware emphemeral networking we use 1528. > > Our network by default is 1500. > > And if I were using jumbo framing, I'd use 9000. > > Please school me, I am a sponge for new knowledge. > We typically change the MTU to the largest (reasonable) values supported by the platform when installing an ethernet switch. I'm not sure if it is the best strategy (feel free to tell me what I've gotten wrong), but it has worked out well so far. We mainly do this to improve the service for our customers: 1) We want to be sure that our customers can get a minimum MTU of 1500 (and 9000 jumbo) for their connections. We see this now and then in customer technical requirements for ethernet circuits. By increasing our MTU, I don't have to worry about the various encapsulation methods that we might use internally for them (MPLS, 802.1q tunneling, etc) reducing their available MTU below the limit; 2) It allows our customers to do their own encapsulation (L2TPv3, MPLS) in addition to ours and still keep 1500/9000 for their payload; 3) In the past we have seen vendor/customer confusion where they believe that MTU and ethernet frame size are the same, by having a little "cush" factor, we don't have to worry about being the bad guy who clobbered their packets if there is terminology confusion; 4) If our customers use Path MTU Discovery they can take advantage of larger MTU sizes and get greater efficiency for their traffic; 5) Many of the Cisco switches require a reboot to change MTU settings. By setting them to their maximum during the initial install we don't have to worry about a service-affecting reboot later if we need to increase it; 6) It doesn't seem to break anything. :-) Steve ######################################################################## To unsubscribe from the MICE-DISCUSS list, click the following link: http://lists.iphouse.net/cgi-bin/wa?SUBED1=MICE-DISCUSS&A=1