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Community Member

Novice questions

Hi. I have several novice questions pertaining to routers.

1. Can anyone tell me the purpose of an auxiliary port?

2. How can you tell if a serial port is for DCE? I tried checking it with the command: sh ip int s0 and with sh int s0 but there is no information there to confirm whether the port is DCE.

3. What is the tftp-server command?

4. What does ' ip-directed broadcast' mean?

5. How does one view icmp logs?

Thanks in advance to anyone who could help.


Re: Novice questions


1.Auxiliary port is used for reverse telnet.

2.U can issue this command sh controllers serial 0

3.i didnt get what u mean,i assume that this is used for auto install





Community Member

Re: Novice questions

Regarding reverse telnet, when is this helpful? I mean why would you need to reverse telnet. Sorry this is the first time i heard about reverse telnet. I would appreciate it if you could expound on the matter.

Hall of Fame Super Blue

Re: Novice questions

Following on from Mahmood's post

3) Use this command if you want the router to be a tftp-server. You may want to do this if you want to copy an IOS off the router to another router.

4) A directed broadcast is a broadcast for all hosts on a particular subnet eg. would be the directed broadcast. It is directed becasue rather than being sent to all hosts it is sent to all hosts within the 192.168.5.x subnet.

5) Not sure what you mean. "sh logging" will show you the router logs.


Community Member

Re: Novice questions

Hi Jon. Thanks for replying. I just have a quick query regarding what you said about directed broadcasts. Is it advisable to disable ip directed broadcasts? Could you tell me the pros and cons of this particular function? Thanks.

Hall of Fame Super Blue

Re: Novice questions

Routers by default will not forward broadcasts but if you allow directed broadcasts then you could initiate a denial of service against a subnet by sending packets to the directed broadcast address and the router will forward the packets onto the subnet.

If you don't need them then disable them. if you do then don't worry too much as there are a lot of other things to worry about security wise :-)


Super Bronze

Re: Novice questions

"5. How does one view icmp logs?"

An ICMP log? Do you have perhaps in mind syslog? If so, "show log" will note the current logging configuration. If a local logging buffer is defined, it will also show recent syslog messages (oldest will be lost from the logging buffer if the buffer overflows).

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