Debug Command on CISCO Router/Switch

Command

Debug

Use

This is a very useful but sometimes dangerous command. It allows you to see how the router or switch processes many different protocols.
If your not careful you can lock yourself out of the device, or even lockup the router/switch so no further traffic will pass!!!!

Syntax

Router#debug

Optional Switches

IUA
aaa
aal2_xgcpspi
access-expression
acircuit
adjacency
alarm-interface
all
alps
apple
arap
archive
arp
asnl
aspp
async
backhaul-session-manager
backup
bcm560x
bgp
bsc
bstun
call
call-admission
call-mgmt
callback
cca
ccaal2
ccfrf11
cch323
ccm-manager
ccsip
ccswvoice
cdapi
cdp
ces-conn
chat
clns
cls
cns
compress
condition
configuration
confmodem
conn
cops
cpc
credentials
crm
crypto
ctunnel
custom-queue
dampening
decnet
dhcp
dialer
dialpeer
diffserv
dlsw
dnsix
domain
dot1x
drip
dsp-resource-manager
dspapi
dspfarm
dspu
dss
dtp
dxi
eigrp
entry
ephone
eswilp
etherchannel
ethernet-interface
event
event-manager
fastethernet
fax
flow-sampler
frame-relay
fras
fras-host
funi
glbp
gssapi
h225
h245
hpi
http
identity
interface
ip
iphc
ipv6
ipx
isis
javascript
kerberos
kron
l2cac
lane
lapb
lapb-ta
lat
ldap
line
list
llc2
lnx
local-ack
management
matm
memory
mgcp
mls
modem
monitor
mop
mpls
mpoa
mrcp
mwi
nbf
ncia
netbios-name-cache
network
nhrp
ntp
nvram
oer
packet
pad
pagp
pm
policy-manager
ppp
pppatm
pppoe
printer
priority
qdm
qllc
qos
radius
rapi
ras
resource
rif
route-map
rpms-proc
rscmon
rtpspi
rtsp
rudpv1
sccp
scp
sdlc
sdllc
serial
sgbp
sgf
smf
sna
snapshot
snmp
source
spanning-tree
srcp
srtp
ssl
sss
standby
stun
sw-vlan
tacacs
tag-switching
tarp
tbridge
tccs
telnet
template
tftp
tgrep
tgrm
token
track
translate
translation
tsp
tunnel
udptn
v120
vlan
voice
voip
vpdn
vpm
vpn
vprofile
vrrp
vtemplate
vtsp
vxml
webvpn
x25
x28
xcctsp
xconnect
xml
ISDN adaptation Layer options
AAA Authentication, Authorization and Accounting
AAL2_XGCP Service Provider Interface.
Boolean access expression
Attachment Circuit information
adjacency
Alarm Interface Card events
Enable all debugging
ALPS debug information
Appletalk information
Appletalk Remote Access
debug archive commands
IP ARP and HP Probe transactions
Application Subscribe Notify Layer
ASPP information
Async interface information
Backhaul SM options
Backup events
BCM560X L2 Driver
BGP information
BSC information
BSTUN information
Call Information
Call admission control
Call Management
Callback activity
CCA activity
ccaal2 information
CCFRF11 information
CCH323 information
Call Manager Application information
CCSIP information
ccswvoice information
CDAPI information
CDP information
Connection Manager CES Client Info
Chat scripts activity
CLNS information
CLS Information
CNS agents
COMPRESS traffic
Condition
Debug Configuration behavior
Modem configuration database
Connection Manager information
COPS
CPC Pak Subblock
credentials service
Carrier Resource Manager info
Cryptographic subsystem
Generic CTunnel Interface
Custom output queueing
Dampening
DECnet information
DHCP client activity
Dial on Demand
Dialpeer info
DiffServ COPS Client
Data Link Switching (DLSw) events
Dnsix information
Domain Name System
Dot1x debugging support
DRiP debug information
DSP Resource Manager Debug
Generic DSP API
DSPFARM Services
DSPU Information
Debug DSS
DTP debug information
atm-dxi information
EIGRP Protocol information
Incoming queue entries
ethernet phone skinny protocol
Eswilp information
EtherChannel/PAgP Shim debugging
Ethernet network interface events
Event related commands
Event manager activity
Fast Ethernet interface information
Fax
Debug flow sampler
Frame Relay
FRAS Debug
FRAS Host Debug
FUNI interface packets
Gateway Load Balancing Protocol (GLBP)
GSSAPI debugs
H.225 Library Debugging
H.245 Library Debugging
HPI (54x) DSP messages
HTTP Debugging
Identity debugging support
Interface Descriptor Block
IP information
IPHC information
IPv6 information
Novell/IPX information
IS-IS Information
Javascript Debugging
KERBEROS authentication and authorization
Kron subsys debugs
Enable/Disable l2cac debug messages
LAN Emulation
LAPB protocol transactions
LAPB Terminal Adapter information
LAT Information
LDAP debug commands
Line debugging
Set interface or/and access list for the next deb command
LLC2 type II Information
generic qllc/llc2 conversion activity
Local ACKnowledgement information
Management applications debugging
Debug Platform Independent Mac Manager
Memory related debugging
Media Gateway Control Protocol
mls debugger information
Modem control/process activation
SPAN debug information
DECnet MOP server events
MPLS debug
MPOA debug options
Media Resource Control Protocol client
mwi debug information
NetBIOS information
Native Client Interface Architecture (NCIA) event
NetBIOS name cache tracing
Network related debugging
NHRP protocol
NTP information
Debug NVRAM behavior
Optimized Exit Routing information
Log unknown packets
X25 PAD protocol
Port Aggregation Protocol
Port Manager debugging
Policy Manager
PPP (Point to Point Protocol) information
PPP over ATM
PPPoE information
LPD printer protocol
Priority output queueing
QoS Device Manager
qllc debug information
QoS debugging
RADIUS protocol
Debug Role API
H.323 RAS Library
Embedded Resource Manager Debug Commands
RIF cache transactions
Route-map
RPMS Process Information
Resource Monitor
RTP Service Provider Interface.
Real Time Streaming Protocol client
RUDP,V1 information
Skinny Client Control Protocol
SCP debugging
SDLC information
SDLLC media translation
Serial interface information
SGBP debugging
Stack Group Forwarding
Software MAC filter
SNA Information
Snapshot activity
SNMP information
Source bridging information
Spanning tree debugging
Simple Resource Coordination Protocol
SRTP Library
SSL Debug command
SSS information
Hot Standby Router Protocol (HSRP)
STUN information
vlan manager
TACACS authentication and authorization
Tag Switching (obsolete use “debug mpls …”)
TARP information
Transparent Bridging
Transparent CCS information
Incoming telnet connections
Template activity
TFTP debugging
tgrep debug
Trunk Group Resource Manager info
Token Ring information
Tracking
Protocol translation events
translation rule information
Telephony Service information
Generic Tunnel Interface
UDPtn async data transport
V120 information
vLAN information
VOICE information
VOIP information
VPDN information
Voice Port Module SPI information
VPN information
Virtual Profile information
Debug Virtual Router Redundancy Protocol
Virtual Template information
Voice Telephony Call Control information
voice xml debug information
WebVPN packet debugs
X.25, CMNS and XOT information
X28 mode
External Call Control TSP information
Xconnect debugs
Debug XML

Example

Since there are many different debugging options, we have added a debugging section with some of the more useful debugs for a CCNA candidate.

R2#debug ip packet
IP packet debugging is on
R2#
*Mar 1 04:35:42.078: IP: s=10.1.1.1 (FastEthernet0/0), d=224.0.0.10, len 60, rcvd 2
*Mar 1 04:35:42.994: IP: s=10.1.1.2 (local), d=224.0.0.10 (FastEthernet0/0), len 60, sending broad/multicast
R2#
*Mar 1 04:35:45.386: IP: s=10.2.2.3 (FastEthernet1/0), d=224.0.0.5, len 80, rcvd 0
R2#
*Mar 1 04:35:46.998: IP: s=10.1.1.1 (FastEthernet0/0), d=224.0.0.10, len 60, rcvd 2
*Mar 1 04:35:47.330: IP: s=10.1.1.2 (local), d=224.0.0.10 (FastEthernet0/0), len 60, sending broad/multicast
R2#
*Mar 1 04:35:48.874: IP: s=10.2.2.2 (local), d=224.0.0.5 (FastEthernet1/0), len 80, sending broad/multicast
R2#
*Mar 1 04:35:51.630: IP: s=10.1.1.1 (FastEthernet0/0), d=224.0.0.10, len 60, rcvd 2
*Mar 1 04:35:51.802: IP: s=10.1.1.2 (local), d=224.0.0.10 (FastEthernet0/0), len 60, sending broad/multicast
R2#
*Mar 1 04:35:55.386: IP: s=10.2.2.3 (FastEthernet1/0), d=224.0.0.5, len 80, rcvd 0
*Mar 1 04:35:56.158: IP: s=10.1.1.2 (local), d=224.0.0.10 (FastEthernet0/0), len 60, sending broad/multicast
R2#
*Mar 1 04:35:56.538: IP: s=10.1.1.1 (FastEthernet0/0), d=224.0.0.10, len 60, rcvd 2
R2#
*Mar 1 04:35:58.874: IP: s=10.2.2.2 (local), d=224.0.0.5 (FastEthernet1/0), len 80, sending broad/multicast
*Mar 1 04:35:59.338: IP: s=10.2.2.2 (local), d=224.0.0.9 (FastEthernet1/0), len 112, sending broad/multicast
R2#
*Mar 1 04:36:00.594: IP: s=10.1.1.2 (local), d=224.0.0.10 (FastEthernet0/0), len 60, sending broad/multicast
*Mar 1 04:36:00.802: IP: s=10.1.1.1 (FastEthernet0/0), d=224.0.0.10, len 60, rcvd 2
R2#
*Mar 1 04:36:04.322: IP: s=10.1.1.1 (FastEthernet0/0), d=224.0.0.9, len 92, rcvd 2
*Mar 1 04:36:04.418: IP: s=10.1.1.2 (local), d=224.0.0.9 (FastEthernet0/0), len 52, sending broad/multicast
*Mar 1 04:36:05.062: IP: s=10.1.1.2 (local), d=224.0.0.10 (FastEthernet0/0), len 60, sending broad/multicast
R2#
*Mar 1 04:36:05.374: IP: s=10.2.2.3 (FastEthernet1/0), d=224.0.0.5, len 80, rcvd 0
*Mar 1 04:36:05.406: IP: s=10.1.1.1 (FastEthernet0/0), d=224.0.0.10, len 60, rcvd 2
R2#
*Mar 1 04:36:08.874: IP: s=10.2.2.2 (local), d=224.0.0.5 (FastEthernet1/0), len 80, sending broad/multicast
R2#
*Mar 1 04:36:09.914: IP: s=10.1.1.2 (local), d=224.0.0.10 (FastEthernet0/0), len 60, sending broad/multicast
*Mar 1 04:36:10.306: IP: s=10.1.1.1 (FastEthernet0/0), d=224.0.0.10, len 60, rcvd 2
R2#do un al
*Mar 1 04:36:14.394: IP: s=10.1.1.2 (local), d=224.0.0.10 (FastEthernet0/0), len 60, sending broad/multicast
*Mar 1 04:36:15.250: IP: s=10.1.1.1 (FastEthernet0/0), d=224.0.0.10, len 60, rcvd 2
*Mar 1 04:36:15.374: IP: s=10.2.2.3 (FastEthernet1/0), d=224.0.0.5, len 80, rcvd 0

You can filter debugs using access-lists to help reduce the output and ease the load on the router.

R2(config)#access-list 101 permit icmp any any
R2(config)#do debug ip packet 101
IP packet debugging is on for access list 101
R2(config)#
*Mar 1 04:38:26.962: IP: tableid=0, s=10.1.1.1 (FastEthernet0/0), d=2.2.2.2 (Loopback0), routed via RIB
*Mar 1 04:38:26.962: IP: s=10.1.1.1 (FastEthernet0/0), d=2.2.2.2, len 100, rcvd 4
*Mar 1 04:38:26.962: IP: tableid=0, s=2.2.2.2 (local), d=10.1.1.1 (FastEthernet0/0), routed via FIB
*Mar 1 04:38:26.966: IP: s=2.2.2.2 (local), d=10.1.1.1 (FastEthernet0/0), len 100, sending
*Mar 1 04:38:27.066: IP: tableid=0, s=10.1.1.1 (FastEthernet0/0), d=2.2.2.2 (Loopback0), routed via RIB
*Mar 1 04:38:27.066: IP: s=10.1.1.1 (FastEthernet0/0), d=2.2.2.2, len 100, rcvd 4
*Mar 1 04:38:27.066: IP: tableid=0, s=2.2.2.2 (local), d=10.1.1.1 (FastEthernet0/0), routed via FIB
*Mar 1 04:38:27.070: IP: s=2.2.2.2 (local), d=10.1.1.1 (FastEthernet0/0), len 100, sending
*Mar 1 04:38:27.130: IP: tableid=0, s=10.1.1.1 (FastEthernet0/0), d=2.2.2.2 (Loopback0), routed via RIB
*Mar 1 04:38:27.130: IP: s=10.1.1.1 (FastEthernet0/0), d=2.2.2.2, len 100, rcvd 4
*Mar 1 04:38:27.130: IP: tableid=0,
R2(config)#s=2.2.2.2 (local), d=10.1.1.1 (FastEthernet0/0), routed via FIB
*Mar 1 04:38:27.134: IP: s=2.2.2.2 (local), d=10.1.1.1 (FastEthernet0/0), len 100, sending
*Mar 1 04:38:27.154: IP: tableid=0, s=10.1.1.1 (FastEthernet0/0), d=2.2.2.2 (Loopback0), routed via RIB
*Mar 1 04:38:27.154: IP: s=10.1.1.1 (FastEthernet0/0), d=2.2.2.2, len 100, rcvd 4
*Mar 1 04:38:27.154: IP: tableid=0, s=2.2.2.2 (local), d=10.1.1.1 (FastEthernet0/0), routed via FIB
*Mar 1 04:38:27.154: IP: s=2.2.2.2 (local), d=10.1.1.1 (FastEthernet0/0), len 100, sending
*Mar 1 04:38:27.170: IP: tableid=0, s=10.1.1.1 (FastEthernet0/0), d=2.2.2.2 (Loopback0), routed via RIB
*Mar 1 04:38:27.170: IP: s=10.1.1.1 (FastEthernet0/0), d=2.2.2.2, len 100, rcvd 4
*Mar 1 04:38:27.170: IP: tableid=0, s=2.2.2.2 (local), d=10.1.1.1 (FastEthernet0/0), routed via FIB
*Mar 1 04:38:27.170: IP: s=2.2.2.2 (local), d=10.1.1.1 (FastEthernet0/0), len 100, sending

Related Articles

guest
0 Comments
Inline Feedbacks
View all comments