Contents

Introduction

Prerequisites

Requirements

Components Used

Conventions

Background Information

Configure

Configurations

Verify

Troubleshoot

Related Information

Introduction

This document describes issues caused when you configure a Jumbo Maximum Transmission Unit (MTU) packet in a Nexus 5000 Series Switch.

Prerequisites

Requirements

There are no specific requirements for this document.

Components Used

The information in this document is based on these series of Nexus switches:

- Nexus 5020

- NX-OS version 4.1(3)N2(1a)

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, ensure that you understand the potential impact of any command.

Conventions

Refer to the Cisco Technical Tips Conventions for more information on document conventions.

Background Information

This document describes the issues that arise when you need to use Jumbo Packet in a Nexus 5000 Series Switch. The scenario described can occur when you try to transfer jumbo packets between Nexus 5000 and/or Nexus 7000 switches.

Configure

The packet loss can happen between two Nexus 5000 switches or between a Nexus 5000 switch and Nexus 7000 switch.

When you ping a host with the packet size of 9216 bytes, you can see packet loss of 50 percent.

Nexus-5000#ping 172.16.0.1 packet-size 9216 count 20

PING 172.16.0.1 (172.16.0.1): 9216 data bytes

9224 bytes from 172.16.0.1: icmp_seq=0 ttl=254 time=6.094 ms

Request 1 timed out

9224 bytes from 172.16.0.1: icmp_seq=2 ttl=254 time=5.507 ms

Request 3 timed out

9224 bytes from 172.16.0.1: icmp_seq=4 ttl=254 time=5.529 ms

Request 5 timed out

9224 bytes from 172.16.0.1: icmp_seq=6 ttl=254 time=10.09 ms

Request 7 timed out

9224 bytes from 172.16.0.1: icmp_seq=8 ttl=254 time=5.597 ms

Request 9 timed out

9224 bytes from 172.16.0.1: icmp_seq=10 ttl=254 time=5.497 ms

Request 11 timed out

9224 bytes from 172.16.0.1: icmp_seq=12 ttl=254 time=5.491 ms

Request 13 timed out

9224 bytes from 172.16.0.1: icmp_seq=14 ttl=254 time=5.555 ms

Request 15 timed out

9224 bytes from 172.16.0.1: icmp_seq=16 ttl=254 time=6.021 ms

Request 17 timed out

9224 bytes from 172.16.0.1: icmp_seq=18 ttl=254 time=5.51 ms

--- 172.16.0.1 ping statistics ---

20 packets transmitted, 10 packets received, 50.00% packet loss

round-trip min/avg/max = 5.491/6.089/10.09 ms

Configurations

If a Jumbo packet has to traverse a Nexus 5020 and a Nexus 7010, you need to configure the Policy-map in Nexus 5020 and set the  system jumbomtu size in the Nexus 7010 Series Switch.

Complete these steps in order to configure the Policy-map in Nexus 5020:

Nexus-5020

!--- You can enable the Jumbo MTU for the whole switch by setting the MTU to its maximum size (9216 bytes)

!--- in the policy map for the default Ethernet system class (class-default).

switch(config)#policy-map type network-qos jumbo

switch(config-pmap-nq)#class type network-qos class-default

switch(config-pmap-c-nq)#mtu 9216

switch(config-pmap-c-nq)#exit

switch(config-pmap-nq)#exit

switch(config)#system qos

switch(config-sys-qos)#service-policy type network-qos jumbo

Refer to Cisco Nexus 5000 Series NX-OS Layer 2 Switching Configuration Guide, Release 4.2(1)N1(1) for more information.

Complete these steps in order to set the jumbo frame in a Nexus 7010 Switch:

Nexus-7010

!--- Set the MTU to its maximum size (9216 bytes) in order to enable the Jumbo MTU for the whole switch.

switch(config)#system jumbomtu 9216

!--- Set the MTU specification for an interface.

switch(config)#interface ethernet x/x

!--- By default, Cisco NX-OS configures Layer 3 parameters. In order to configure Layer 2 parameters, use this command.

switch(config-if)#switchport

switch(config-if)#mtu 9216

switch(config-if)#exit

Verify

In order to verify, you can ping with a packet size of more than 1500 bytes: Ping -l 9000 x.x.x.x .

You can also issue the  show interface ethernet port/slot  command in order to verify if the Jumbo frame is set.

On the Nexus 5000, enter the  show queuing interface ethernet 1/1  command:

Nexus5000#show queuing interface ethernet 1/1

Ethernet1/1 queuing information:

TX Queuing

qos-group  sched-type  oper-bandwidth

0       WRR             50

1       WRR             50

RX Queuing

qos-group 0

q-size: 243200, HW MTU: 9280 (9216 configured)

On the Nexus 7000, enter the  show interface ethernet 1/9  command:

Nexus-7010#show interface ethernet 1/9

Ethernet1/9 is up

Hardware: 10000 Ethernet, address: 0000.0000.0000 (bia 0000.0000.0000)

MTU 9216 bytes, BW 10000000 Kbit, DLY 10 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA

Port mode is access

full-duplex, 10 Gb/s, media type is 10g

Beacon is turned off

Auto-Negotiation is turned off

Input flow-control is off, output flow-control is off

Rate mode is dedicated

Switchport monitor is off

Last link flapped 00:57:24

Last clearing of "show interface" counters 00:56:14

30 seconds input rate 0 bits/sec, 0 packets/sec

30 seconds output rate 360 bits/sec, 0 packets/sec

Load-Interval #2: 5 minute (300 seconds)

input rate 0 bps, 0 pps; output rate 448 bps, 0 pps

RX

5894254 unicast packets  0 multicast packets  0 broadcast packets

5894254 input packets  29108950332 bytes

0 jumbo packets  0 storm suppression packets

0 runts  0 giants  0 CRC  0 no buffer

0 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

5894228 unicast packets  2225 multicast packets  0 broadcast packets

5896453 output packets  29109001641 bytes

0 jumbo packets

0 output error  0 collision  0 deferred  0 late collision

0 lost carrier  0 no carrier  0 babble

0 Tx pause

0 interface resets

Note: The Jumbo counter on Nexus 7000 series is not supported and the Tx and Rx frames show null value, but if you note the MTU size it displays the configured Jumbo frame.

Troubleshoot

There is currently no information available to troubleshoot this configuration.

Related Information

- Cisco Nexus 5000 Series Switches

- Cisco Nexus 7000 Series Switches Support Page

- Cisco Technical Support & Downloads