Cisco Nexus 7000 Series NX-OS Troubleshooting Guide -- Troubleshooting Unicast Traffic

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This article provides information on how to troubleshoot unicast packet flow traffic issues for the M1 Series modules.

Step 1: Packet is Received into Interface from Wire

During this step, the packet is received into the Nexus 7000 port. When troubleshooting this step, we want to look to ensure there is transceiver interoperability, and validate whether we are seeing any errors on the interface. We do this via using the following commands

  • show interface <interface>
  • show interface <interface> transceiver

PHX2-N7K-1# show interface e1/1

 Ethernet1/1 is up
 Hardware: 10000 Ethernet, address: 0024.986c.00b0 (bia 0024.986c.00b0)
 Description: N7K-vdc-1 connecting to core 6506
 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
 Auto-Negotiation is turned off
 Input flow-control is off, output flow-control is off
 Rate mode is shared
 Switchport monitor is off 
 Last link flapped 7week(s) 4day(s)
 Last clearing of "show interface" counters never
 1 minute input rate 13056 bits/sec, 9 packets/sec
 1 minute output rate 4608 bits/sec, 0 packets/sec
   341190251 input packets 276211313 unicast packets 52112947 multicast packets
   12865991 broadcast packets 0 jumbo packets 0 storm suppression packets
   94295027129 bytes
   462437316 output packets 85121 multicast packets
   188251 broadcast packets 0 jumbo packets
   648159081064 bytes
   0 input error 0 short frame 0 watchdog
   0 no buffer 0 runt 0 CRC 0 ecc
   0 overrun  0 underrun 0 ignored 0 bad etype drop
   0 bad proto drop 0 if down drop 0 input with dribble
   0 input discard
   0 output error 0 collision 0 deferred
   0 late collision 0 lost carrier 0 no carrier
   0 babble
   0 Rx pause 0 Tx pause
 1 interface resets

PHX2-N7K-1# show interface e1/1 transceiver details

   sfp is present
   name is CISCO-AVAGO     <<< If this says type is (unknown), it is not supported.
   part number is SFBR-7700SDZ    
   revision is B4  
   serial number is AGD12434116     
   nominal bitrate is 10300 MBits/sec
   Link length supported for 50/125um fiber is 82 m(s)
   Link length supported for 62.5/125um fiber is 26 m(s)
   cisco id is --
   cisco extended id number is 4
          SFP Detail Diagnostics Information (internal calibration)
                                    Alarms                  Warnings
                               High        Low         High          Low
 Temperature   45.46 C        75.00 C     -5.00 C     70.00 C        0.00 C
 Voltage        3.28 V         3.63 V      2.97 V      3.46 V        3.13 V
 Current        6.92 mA       10.50 mA     2.50 mA    10.50 mA       2.50 mA
 Tx Power       -2.75 dBm       1.69 dBm  -11.30 dBm   -1.30 dBm     -7.30 dBm
 Rx Power       -2.43 dBm       1.99 dBm  -13.97 dBm   -1.00 dBm     -9.91 dBm
 Transmit Fault Count = 0
 Note: ++  high-alarm; +  high-warning; --  low-alarm; -  low-warning

Step 2: Linksec Decryption Occurs, 1st stage Port QoS

In step 2, Linksec decryption occurs as well as receive side stage 1 QoS.

It is important to step back and evaluate the difference between stage 1 and stage 2 QoS. The difference is that some ports can be configured in shared mode, whereas some can be configured in dedicated mode, on the 10G modules. What this means, is that there is 10g of bandwidth that can be dedicated to a port or shared amongst ports (4 ports, on the m132 module).

When running in shared mode, there exists a chance for contention accessing the 10g bandwidth through the 4:1 Mux. To alleviate this, some QoS intelligence was passed down to the 4:1 Mux which aggregates the ports.

In dedicated mode, there is no QoS applied at the Mux, instead, all traffic is processed in phase 2 QoS. To summarize, in shared mode, 1st stage QoS ensures fair access to the 10g of port bandwidth. In both shared and dedicated mode, 2nd stage QoS occurs to provide ingress queuing to the system.

For the ingress QoS, we are concerned about the Receive side QoS parameters in the show queuing command.

Use the show policy-map command to see per queue dropped packets.

The commands to troubleshoot Linksec and Port QoS are as follows:

  • show cts interface [all | interface]
  • show queuing interface interface
  • show policy-map interface (for per queue drop)

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