Unfortunately, we're using ME3400s, and you cannot specify MTU on a per interface basis...
Ben Steele wrote: > Your better off just running system mtu 1504(if you want to deliver > QinQ to customers) and then specifying the larger mtu frames on your > trunk interfaces, this still restricts your customer access ports to > 1504 while allowing you to run what you need, jumbo frame mtu on an > interface will override the system "baby jumbo" mtu command. > > On 27/03/2008, at 12:12 PM, Dan Armstrong wrote: > >> The reason I don't want to raise it too high - is if we're selling TLS >> services to a customer, (ie a VLAN provisioned on 2 ports on different >> switches, carried across our core/trunks) - I don't want them being able >> to send any packet larger than 1500 byes. >> >> A bit bigger wouldn't be a problem, but if I set it to, say 9000, and >> all of a sudden we have some jackass with a storage head that could be >> firing 9000 byte packet across our backbone... not cool, I believe it >> would cause havoc with "small packet" applications like VoIP, even with >> QoS, the bit-time to send a 9000 byte packet out an interface is >> significant. >> >> I've also never been too clear on the interaction between the system mtu >> command, and the system mtu jumbo command. I've always just made them >> match... >> >> >> >> >> >> Peter Rathlev wrote: >>> On Wed, 2008-03-26 at 19:01 -0400, Dan Armstrong wrote: >>> >>>> I've been bashing my head against the wall all day for a definitive >>>> answer on this: >>>> >>>> On a Cisco switch that supports QinQ (3550, 3750, ME3400, 3560 etc) >>>> >>>> >>>> What is the _minimum_ value I need to set the system MTU to, to do >>>> QinQ? 1504? 1522? 1526? 1546? >>>> >>>> I can't seem to find one concise answer... >>>> >>> >>> I'm not entirely sure what the "system mtu" specifies, i.e. if it's >>> interface MTUs (typically excluding data link headers) or what. >>> >>> IPv4 packet = 1500 bytes. Ethernet header = 14 bytes. 802.1q header = 4 >>> bytes. Another one = 4 bytes more. So for "simple" QinQ of "regular" >>> IPv4 traffic it would be max 1522 bytes of data per packets. >>> >>> Any special reason not to just raise it to the maximum of 2000 bytes? >>> >>> Regards, >>> Peter >>> >>> >>> >> >> _______________________________________________ >> cisco-nsp mailing list [email protected] >> https://puck.nether.net/mailman/listinfo/cisco-nsp >> archive at http://puck.nether.net/pipermail/cisco-nsp/ > _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
