Cisco Nexus 7000 Series NX-OS Troubleshooting Guide -- Troubleshooting Packet Flow Issues
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This article describes how to troubleshoot packet flow issues for Cisco NX-OS.
Contents |
Packet Flow Issues
Packets could be dropped for the following reasons :
- Software switched packets could be received from the interface, but dropped by the supervisor because of rate limits.
- Packets could be dropped because of a QoS policy.
- Hardware switched packets could be dropped by the hardware because of a bandwidth limitation.
Packets Dropped Because of Rate Limits
Use the show hardware rate-limit command to determine if packets are being dropped because of a rate limit.
dctl-n7010-7# show hardware rate-limit copy Units for Config: packets per second Allowed, Dropped & Total: aggregated since last clear counters Rate Limiter Class Parameters ------------------------------------------------------------ copy Config : 30000 Allowed : 13651778 Dropped : 228295 <-- caused by ICMP redirect or OSPF Hello Total : 13880073
dctl-n7010-7(config)# show hardware rate-limit module 1 Units for Config: packets per second Allowed, Dropped & Total: aggregated since last clear counters Rate Limiter Class Parameters ------------------------------------------------------------ layer-3 mtu Config : 500 Allowed : 0 Dropped : 0 Total : 0 layer-3 ttl Config : 500 Allowed : 0 Dropped : 0 Total : 0 layer-3 control Config : 10000 Allowed : 17020000 Dropped : 88790262 <---HSRP, OSPF hello Total : 105810262 layer-3 glean Config : 100 Allowed : 0 Dropped : 0 Total : 0 layer-3 multicast directly-connected Config : 3000 Allowed : 0 Dropped : 0 Total : 0 layer-3 multicast local-groups Config : 3000 Allowed : 0 Dropped : 0 Total : 0 layer-3 multicast rpf-leak Config : 500 Allowed : 0 Dropped : 0 Total : 0 layer-2 storm-control Config : Disabled access-list-log Config : 100 Allowed : 0 Dropped : 0 Total : 0 copy Config : 30000 Allowed : 552173 Dropped : 0 Total : 552173 receive Config : 30000 Allowed : 85134 Dropped : 0 Total : 85134 layer-2 port-security Config : Disabled
Packets Dropped Because of a QoS Policy
Use the show policy-map interface control-plane command to determine if packets are being dropped because of a QoS policy.
dctl-n7010-7# sh policy-map interface control-plane class-map copp-system-class-exception (match-any) match exception ip option match exception ip icmp unreachable police cir 360 kbps , bc 250 ms module 1 : conformed 0 bytes; action: transmit violated 0 bytes; action: drop module 2 : conformed 0 bytes; action: transmit violated 0 bytes; action: drop module 3 : conformed 0 bytes; action: transmit violated 0 bytes; action: drop module 4 : conformed 0 bytes; action: transmit violated 0 bytes; action: drop module 10 : conformed 11614462878 bytes; action: transmit violated 3097405384908 bytes; action: drop
Packets Dropped in Hardware
Use the following show hardware commands to determine if packets are being dropped by the hardware.
- show hardware internal statistics rates
- show hardware internal statistics pktflow all
show hardware internal statistics rates
dctl-n7k-dist-1# sh hardware internal statistics rates + ============================= + R2D2 Instance 0 + ============================= | |-- Ingress IN | |--- Packets/sec | | |--- sum: 0 | | | |--- Bytes/sec | | |--- sum: 0 | |-- Ingress OUT | |--- Packets/sec | | |--- sum: 0 | | | |-- Egress IN | |--- Packets/sec | | |--- sum: 0 | | | |-- Egress OUT | |--- Packets/sec | | |--- sum: 0 | | | |--- Bytes/sec | | |--- sum: 0 | | | + ============================= + Metropolis Instance 0 + ============================= | |-- Ingress IN | |--- Packets/sec | | |--- I1: 2 | | |--- I1: 0 | | |--- sum: 0 | | | |-- Ingress OUT | |--- Packets/sec | | |--- I1: 2 | | |--- I1: 0 | | |--- sum: 0 | | | |--- Bytes/sec | | |--- I1: 1166 | | |--- I1: 0 | | |--- sum: 0 | |-- Egress IN | |--- Packets/sec | | |--- I1: 0 | | |--- I1: 0 | | |--- sum: 0 | | | |--- Bytes/sec | | |--- I1: 0 | | |--- I1: 0 | | |--- sum: 0 | |-- Egress OUT | |--- Packets/sec | | |--- I1: 0 | | |--- sum: 0 | | | | |
show hardware internal statistics pktflow all
This command displays per ASIC statistics, including packets into and out of the ASIC. This command helps to identify where packet loss is occurring.
dctl-n7k-dist-1# show hardware internal statistics pktflow all bhv_bitmask:0 |------------------------------------------------------------------------| | Device:R2D2 Role:MAC | | Packets |------------------------------------------------------------------------| Instance: 0 Ports:- |----------|-------------------|------------------| | | IN | OUT | |----------|-------------------|------------------| |Ingress | 00000000014a40c0 | 00000000014a40c0 | |----------|-------------------|------------------| |Egress | 000000000007e9dc | 000000000007e9dc | |----------|-------------------|------------------| |------------------------------------------------------------------------| | Device:Metropolis Role:REWR | | Packets |------------------------------------------------------------------------| Instance: 0 Ports:- |----------|-------------------|------------------| | | IN | OUT | |----------|-------------------|------------------| |Ingress | 00000000014a40c0 | 0000000001498ccc | |----------|-------------------|------------------| |Egress | 000000000007e9dc | 000000000007e9dc | |----------|-------------------|------------------| |------------------------------------------------------------------------| | Device:Octopus Role:QUE | | Packets |------------------------------------------------------------------------| Instance: 0 Ports:- |----------|-------------------|------------------| | | IN | OUT | |----------|-------------------|------------------| |Ingress | 0000000001498ccc | 0000000001498cc6 | |----------|-------------------|------------------| |Egress | 000000000007e9c5 | 000000000007e9dc | |----------|-------------------|------------------| *** Counters above represent packets combined into a larger one ***