MTU and jumbo frame on nexus 9k
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04-18-2019 05:45 AM
I'm seeing jumbo frame incrementing RX and TX however show interface shows MTU set at 1500.
port-channel51 is up
admin state is up,
vPC Status: Up, vPC number: 51
Hardware: Port-Channel, address: 00b7.712e.4580 (bia 00b7.712e.4580)
Description: bondup
MTU 1500 bytes, BW 160000000 Kbit, DLY 10 usec
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, medium is broadcast
Port mode is trunk
full-duplex, 40 Gb/s
Input flow-control is off, output flow-control is off
Auto-mdix is turned off
Switchport monitor is off
EtherType is 0x8100
Members in this channel: Eth1/51, Eth1/52, Eth1/53, Eth1/54
Last clearing of "show interface" counters 18:33:21
0 interface resets
30 seconds input rate 6279336 bits/sec, 1294 packets/sec
30 seconds output rate 4351224 bits/sec, 898 packets/sec
Load-Interval #2: 5 minute (300 seconds)
input rate 21.68 Mbps, 2.41 Kpps; output rate 7.79 Mbps, 1.09 Kpps
RX
342713802 unicast packets 10582812 multicast packets 8336704 broadcast packets
361653357 input packets 434870808283 bytes
262958908 jumbo packets 0 storm suppression bytes
0 runts 20039 giants 0 CRC 0 no buffer
20039 input error 0 short frame 0 overrun 0 underrun 0 ignored
0 watchdog 0 bad etype drop 0 bad proto drop 0 if down drop
0 input with dribble 0 input discard
0 Rx pause
TX
164370593 unicast packets 2305329 multicast packets 79862 broadcast packet
s
167274585 output packets 155818320925 bytes
83969134 jumbo packets
518801 output error 0 collision 0 deferred 0 late collision
0 lost carrier 0 no carrier 0 babble 0 output discard
0 Tx pause
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04-18-2019 06:07 AM
is it set somewhere globally ? with this system jumbomtu 9216 or something similar
that would override the interface settings
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04-18-2019 06:16 AM
it's not set globally but I've just read this :
In the case of 40-G interfaces, since the MTU limit check is disabled, it ignores the packet size and traffic flows irrespective of its MTU.
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04-18-2019 06:38 AM
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04-18-2019 06:43 AM
In the case of 40-G interfaces, since the MTU limit check is disabled, it ignores the packet size and traffic flows irrespective of its MTU.
Eth1/51, Eth1/52, Eth1/53, Eth1/54
So, this is not a 40G interface natively. These are 4 10Gigs.
HTH
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04-18-2019 06:45 AM
