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Cisco ASR 1000 Series Aggregation Services Routers Software Configuration Guide
OL-16506-17
Chapter 21 Packet Trace
Configuration Examples for Packet Trace
Router# debug platform packet-trace packet 2048 summary-only
Router# debug platform condition start
Router# debug platform condition stop
Router# show platform packet-trace summary | include DROP
403 Gi0/0/0 --- DROP 064.NatIn2Out
781 Gi0/0/0 --- DROP 064.NatIn2Out
1708 Gi0/0/0 --- DROP 064.NatIn2Out
The output shows that packets are dropped due to NAT configuration on Gigabit Ethernet interface 0/0/0,
which enables you to understand that an issue is occurring on a specific interface. Using this information,
you can limit which packets to trace, reduce the number of packets for data capture, and increase the
level of inspection.
Router# debug platform packet-trace enable
Router# debug platform packet-trace packet 256
Router# debug platform packet-trace copy packet input size 32 L3
Router# debug platform condition interface Gi0/0/0
Router# debug platform condition start
Router# debug platform condition stop
Router# show platform packet-trace summary | include DROP
14 Gi0/0/0 --- DROP 064.NatIn2Out
Router# show platform packet-trace 14
Packet: 14 CBUG ID: 17
Summary
Input : GigabitEthernet0/0/0
Output : ---
State : DROP 064.NatIn2Out
Timestamp: 1123438869354000
Path Trace
Feature: IPv4
Source : 10.1.1.1
Destination : 64.102.6.247
Protocol : 17 (UDP)
Feature: NAT
Direction : IN to OUT
Action : Drop
Sub-code : 027 - NON_PATTABLE
Feature: DROP
Code: 064.NatIn2Out
Packet Copy In
45000040 00020000 3C11E030 0A010101 406606F7 046D0035
From the show command output, you can see that there is some traffic that cannot be configured for Port
Address Translation (PAT). Hence, you should modify the ACL to spare this traffic from NAT
configuration, or disable the service for that kind of traffic. From the copy of the incoming packet, you
can see that the protocol is UDP, and the destination port is DNS, and that you should turn off the DNS
Application Layer Gateway (ALG).