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nexus ping drops

Unanswered Question
Jan 9th, 2014
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Hi,


We have a nexus 5k acting as core in one of our sites.


Problem:- When a user connects himself to nexus 2k port, the connectivity suddenly drops & ping message are gone with either destination host uncreachable or ping failure messages.

This has been observer on many users.



class-map type qos class-fcoe

class-map type queuing class-fcoe

  match qos-group 1

class-map type queuing class-all-flood

  match qos-group 2

class-map type queuing class-ip-multicast

  match qos-group 2

class-map type network-qos class-fcoe

  match qos-group 1

class-map type network-qos class-all-flood

  match qos-group 2

class-map type network-qos class-ip-multicast

  match qos-group 2


We saw these configurations on the switch. will these cauese any problems?

Appreciate if some suggestions come up!





Appreciate all help!

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Overall Rating: 4 (2 ratings)
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richbarb Thu, 01/09/2014 - 20:47
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  • Cisco Employee,

Hi,


This configuration that you pasted is about QoS, by default all traffic different of FCoE is marked as class-group 0 or not marked in fact (except some control plane traffic as well).

I really believe this is something not related with QoS configuration, probably routing stuff or drops by some firewall in the middle.


How's your N2K interface count error?

Did you looked by duplicate mac address?

Routing unstable?


Regards,

Richard

suthomas1 Fri, 01/10/2014 - 23:00
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Thanks Richard.


Routing looks fine, the only thing that can be seen on the n5k is some flow control receive status on/off messages.Apart from that, rest looks good.


Any specific commands to check what might be happening.


Appreciate all inputs.

suthomas1 Mon, 01/13/2014 - 20:40
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The ping target is the SVI on nexus. but few devices on this segment work fine whereas few others have this problem.

Steve Fuller Mon, 01/13/2014 - 23:45
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  • Community Spotlight Award,

    Member's Choice, September 2015

Hi,

Depending upon which Nexus platform and which NX-OS version you're running, it's quite possibly the Control Plane Policing (CoPP) feature, introduced in NX-OS 5.1(3)N1(1), that's causing the drops.


You can see if that's the case using the show policy-map interface control-plane and look for incrementing violations in the class that matches ICMP. There's a fair amount of information in the output so I find the quickest way to spot this is using the show policy-map interface control-plane | in "class|violate" command and look for a non zero value. Assuming the default configuration, on the Nexus 5000 this will be the copp-system-class-icmp-echo


You can find further information about CoPP in the Configuring Control Plane Policing section of the Nexus 5000 Security Configuration Guide.


Regards

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