Discards - vEdge Interface

[bradleyordner]

Hi, 

I see a lot of inbound discards on my ISP interfaces attached to my vEdge 5ks. Is there any commands I can use to narrow it down? There is a command - show interfaces errors, but is the error the actual discard?

Brad 

[ekhabaro]

yes, most of the times, see this example from the TAC lab:

vEdge1# show interface statistics ge0/0

                                                                                                                   PPPOE  PPPOE  DOT1X  DOT1X
                AF    RX                  RX      RX      TX                  TX      TX     RX   RX    TX   TX    TX     RX     TX     RX
VPN  INTERFACE  TYPE  PACKETS  RX OCTETS  ERRORS  DROPS   PACKETS  TX OCTETS  ERRORS  DROPS  PPS  Kbps  PPS  Kbps  PKTS   PKTS   PKTS   PKTS
-----------------------------------------------------------------------------------------------------------------------------------------------
0    ge0/0      ipv4  3765674  651559865  0       404487  3228700  594411312  0       2      16   21    13   17    -      -      0      0

vEdge1# show interface errors ge0/0
interface vpn 0 interface ge0/0 af-type ipv4
 arp-add-fails           72991
 rx-arp-reply-drops      0
 rx-arp-rate-limit-drops 0
 tx-arp-rate-limit-drops 1
 rx-arp-non-local-drops  399704
 tx-arp-request-fail     0
 tx-no-arp-drops         1
 rx-ip-ttl-expired       0
 interface-disabled      0
 rx-policer-drops        0
 rx-non-ip-drops         0
 filter-drops            0
 mirror-drops            0
 cpu-policer-drops       4791
 tx-icmp-policer-drops   0
 tx-icmp-mirrored-drops  0
 split-horizon-drops     0
 route-lookup-fail       0
 bad-label               0
 rx-policer-remark       0
vEdge1#

If you sum up cpu-policer-drops and rx-arp-non-local-drops drops, you will get RX drops from the interface statistics. 

[bradleyordner]

Thanks, I have a similar output. Is it normal to discard so much non local
ARP? This isn’t considered broadcasts is it?

I have my next hop constantly arping for my address although i see it in
tcp dump so it isn’t discarded I believe.

Is there any debugs to capture discards?

[ekhabaro]

yes it's normal. 

rx-arp-non-local-drop — Received ARP packets that do not match the destination IP address of any local IP address.

https://www.cisco.com/c/en/us/td/docs/routers/sdwan/command/sdwan-cr-book/operational-cmd.html#wp3001399095 

These packets may be counted under broadcast counter as well most likely, but not sure.

> Is there any debugs to capture discards?

tcpdump ?

[bradleyordner]

I tired this, but found discrepancy.

RX Drops - 57 

NON Local - 45

No policer yet. 

Ill keep my eye on it. As long as it does not impact any performance? 

[pgasparovic]

Sometimes just double-check if switch and VPN0 trunk a and service VPN subint configurations match as was my today case greatly overlooking that due to some forgotten experiments the switch was in access and vEdge in trunk, so ARPs were plain dropped.