ARP / Router CPU History / TTL and DNS
So far during my studies, i came across ARP, Router CPU history, TTL value of a packet and DNS working.
To check ARP table on a CISCO router:
#show ip arp
It will display all the resolved addresses that are present on a router. Cisco router will keep ARP entry for around 4 hours. Off-course you do know ARP stands for Address Resolution Protocol.
DNS: Domain name System can either use UDP or TCP port 53. If a host is trying to resolve some domain name, it will send request using UDP to port 53 but if DNS doesn't respond, then the host will try sending request using DNS TCP port 53. UDP -- > TCP (53)
TTL (Time to Live) : Yes this field is used in data packet to make its life easy :) Each router through which the packet passes, will decrement the TTL value in data packet ( TTL value starts from 255) by one. Once it reaches zero, the packet will be discarded and hence it (Packet) will not circulate for ever. Just imagine if there was no TTL field in the packets which are roaming wildly the global internet !
MTU: Maximum transmission unite is 1500 bytes. its the maximum packet a router can transmit.
#show processes & #show processes cpu history
R1#show processes
CPU utilization for five seconds: 2%/0%; one minute: 0%; five minutes: 0%
PID QTy PC Runtime (ms) Invoked uSecs Stacks TTY Process
1 Cwe 6001F598 0 2 0 5664/6000 0 Chunk Manager
2 Csp 609F9CDC 0 2520 0 2524/3000 0 Load Meter
3 Lwe 611F71B8 8 436 18 5500/6000 0 CEF Scanner
4 Mwe 61D95244 0 1 023372/24000 0 EDDRI_MAIN
5 Lst 6001C4B0 6760 1384 4884 5416/6000 0 Check heaps
6 Cwe 60023228 0 1 0 5656/6000 0 Pool Manager
7 Mst 60F8C9B4 0 2 0 5496/6000 0 Timers
8 Mwe 600B448C 0 211 0 5700/6000 0 IPC Dynamic Cach
9 Mwe 600A59F4 0 1 0 5692/6000 0 IPC Zone Manager
10 Mwe 600A4C5C 36 12593 2 5608/6000 0 IPC Periodic Tim
11 Mwe 600A4AAC 44 12593 3 5632/6000 0 IPC Deferred Por
12 Mwe 600A56CC 0 1 0 5564/6000 0 IPC Seat Manager
13 Mwe 600AACD0 4 1 4000 5660/6000 0 IPC BackPressure
14 Mwe 60253CA4 0 1 011664/12000 0 OIR Handler
15 Mwe 60458374 0 1 023600/24000 0 Crash writer
16 Msi 6055E184 0 421 0 5492/6000 0 Environmental mo
17 Mwe 60B669BC 4 213 18 5648/6000 0 ARP Input
18 Mwe 60BC0B50 0 2 0 5448/6000 0 ATM Idle Timer
19 Mwe 60F48894 0 2 0 5484/6000 0 AAA high-capacit
20 Lwe 60F4C6C0 0 1 0 5688/6000 0 AAA_SERVER_DEADT
21 Mwe 60FB2F60 0 1 011644/12000 0 Policy Manager
--More--
To check ARP table on a CISCO router:
#show ip arp
It will display all the resolved addresses that are present on a router. Cisco router will keep ARP entry for around 4 hours. Off-course you do know ARP stands for Address Resolution Protocol.
DNS: Domain name System can either use UDP or TCP port 53. If a host is trying to resolve some domain name, it will send request using UDP to port 53 but if DNS doesn't respond, then the host will try sending request using DNS TCP port 53. UDP -- > TCP (53)
TTL (Time to Live) : Yes this field is used in data packet to make its life easy :) Each router through which the packet passes, will decrement the TTL value in data packet ( TTL value starts from 255) by one. Once it reaches zero, the packet will be discarded and hence it (Packet) will not circulate for ever. Just imagine if there was no TTL field in the packets which are roaming wildly the global internet !
MTU: Maximum transmission unite is 1500 bytes. its the maximum packet a router can transmit.
#show processes & #show processes cpu history
R1#show processes
CPU utilization for five seconds: 2%/0%; one minute: 0%; five minutes: 0%
PID QTy PC Runtime (ms) Invoked uSecs Stacks TTY Process
1 Cwe 6001F598 0 2 0 5664/6000 0 Chunk Manager
2 Csp 609F9CDC 0 2520 0 2524/3000 0 Load Meter
3 Lwe 611F71B8 8 436 18 5500/6000 0 CEF Scanner
4 Mwe 61D95244 0 1 023372/24000 0 EDDRI_MAIN
5 Lst 6001C4B0 6760 1384 4884 5416/6000 0 Check heaps
6 Cwe 60023228 0 1 0 5656/6000 0 Pool Manager
7 Mst 60F8C9B4 0 2 0 5496/6000 0 Timers
8 Mwe 600B448C 0 211 0 5700/6000 0 IPC Dynamic Cach
9 Mwe 600A59F4 0 1 0 5692/6000 0 IPC Zone Manager
10 Mwe 600A4C5C 36 12593 2 5608/6000 0 IPC Periodic Tim
11 Mwe 600A4AAC 44 12593 3 5632/6000 0 IPC Deferred Por
12 Mwe 600A56CC 0 1 0 5564/6000 0 IPC Seat Manager
13 Mwe 600AACD0 4 1 4000 5660/6000 0 IPC BackPressure
14 Mwe 60253CA4 0 1 011664/12000 0 OIR Handler
15 Mwe 60458374 0 1 023600/24000 0 Crash writer
16 Msi 6055E184 0 421 0 5492/6000 0 Environmental mo
17 Mwe 60B669BC 4 213 18 5648/6000 0 ARP Input
18 Mwe 60BC0B50 0 2 0 5448/6000 0 ATM Idle Timer
19 Mwe 60F48894 0 2 0 5484/6000 0 AAA high-capacit
20 Lwe 60F4C6C0 0 1 0 5688/6000 0 AAA_SERVER_DEADT
21 Mwe 60FB2F60 0 1 011644/12000 0 Policy Manager
--More--
its quite a detailed command, showing memory utilization for each running process and as you can expect there are a lot of processes running on a CISCO router to enable the magic on it. One more output for your consideration, i would personally recommend below mentioned command, which plot a nice graph of the cpu utilization:
R1#show processes cpu history
R1 03:32:13 AM Friday Mar 1 2002 UTC
22211111
100
90
80
70
60
50
40
30
20
10
0....5....1....1....2....2....3....3....4....4....5....5....6
0 5 0 5 0 5 0 5 0 5 0
CPU% per second (last 60 seconds)
112 11 1111 111 111 111 1 1 11 1 1 11 1 213
100
90
80
70
60
50
40
30
20
10
0....5....1....1....2....2....3....3....4....4....5....5....6
0 5 0 5 0 5 0 5 0 5 0
CPU% per minute (last 60 minutes)
* = maximum CPU% # = average CPU%
342
100
90
80
70
60
50
40
30
20
10
0....5....1....1....2....2....3....3....4....4....5....5....6....6....7..
0 5 0 5 0 5 0 5 0 5 0 5 0
CPU% per hour (last 72 hours)
* = maximum CPU% # = average CPU%
I hope you enjoyed reading above post. Please do comment and let me know your feedback, please also post your questions and confusions in below comments box. Thanks
Categories:
ARP,
CCNA Dumps,
CCNA Notes,
CPU,
CPU Router History,
DNS,
Domain Name Server,
IOS,
Time to Live,
TTL
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