Nexus 500 MTU Explanation

[Jean-Christophe]

Hi Guys,

Can someone explain to me the MTU configuration on Nexus 5500?

I have MTU set globally to jumbo as bellow:

policy-map type network-qos jumbo
class type network-qos class-default
mtu 9216
multicast-optimize
system qos
service-policy type network-qos jumbo

When I look at interface MTU queuing, I see the MTU is correct:

gefdc02# sh queuing interface e1/37
Ethernet1/37 queuing information:
TX Queuing
qos-group sched-type oper-bandwidth
0 WRR 100

RX Queuing
qos-group 0
q-size: 469760, HW MTU: 9216 (9216 configured)
drop-type: drop, xon: 0, xoff: 469760
Statistics:
[...]
Per-priority-pause status : Rx (Inactive), Tx (Inactive)

Total Multicast crossbar statistics:
Mcast pkts received from the cross-bar : 99461929

But when I look at interface itself, MTU is still 1500:

gefdc02# sh int e1/37
Ethernet1/37 is up
Dedicated Interface
Belongs to Po45
Hardware: 1000/10000 Ethernet, address: 002a.6ad8.05ac (bia 002a.6ad8.05ac)
Description: fonesxcore01-esx
MTU 1500 bytes, BW 10000000 Kbit, DLY 10 usec
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA
Port mode is trunk
full-duplex, 10 Gb/s, media type is 10G
Beacon is turned off
Input flow-control is off, output flow-control is off
Rate mode is dedicated
Switchport monitor is off
EtherType is 0x8100
[...]

Also, note that interface e1/37 is member of a Port-Channel which in turn is member of a vPC.

Is it a normal behavior?

Thanks & Best Regards,

Jean-Christophe

[Mark Malone · Accepted solution]

Hi
Thats right just the way 5K is , its set globally , on 9k you can actually change it per interface but once you have set it as globally on 5k thats right , we have it set ourselves , the 9ks you will actually see it under interface too

mine

policy-map type network-qos jumbo
class type network-qos class-default
mtu 9216
multicast-optimize

sh int e1/10 | i MTU
# MTU 1500 bytes, BW 10000000 Kbit,, BW 10000000 Kbit, DLY 10 usec