[c-nsp] How can I increase Ethernet MTU?

Victor Sudakov vas at mpeks.tomsk.su
Sun Jan 25 23:02:02 EST 2015

Lukas Tribus wrote:
> >
> > Soon we will be enabling MPLS on some routers connected to this
> > network, so the switches will have to handle frames with the MTU
> > larger than the default 1500 bytes.
> >
> > How do I configure the switches to pass frames with MTU=1600, if
> > possible, without disrupting the service?
> >
> > I will be grateful for a link to some good howto.
> http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750x_3560x/software/release/12-2_53_se/configuration/guide/3750xscg/swtunnel.html#wp1042950

There is one more point. Some switches are connected via
communications equipment (e.g. iPASOLINK radio relay) rather than
directly. Those switches' GigabitEthernet ports are running in the
100Mb/s mode because the iPASOLINK equipment has FastEthernet ports
with maximum frame size = 2000.

Does the "system mtu jumbo" affect GigabitEthernet ports in 100Mb/s
mode? Is anything larger than 1500 supported in 100Mb/s mode on Cisco?

Victor Sudakov,  VAS4-RIPE, VAS47-RIPN
sip:sudakov at sibptus.tomsk.ru

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