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 listllc2 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