# Status of interfaces



## m69 (Sep 24, 2012)

Hi 
I want to understand when a connection is ok, It means that when the other connection side is up,Status of interfaces become up when the other side has an ip,even it doesn't up.
Is there any service or option that show me when the other side's interface is up ?
Thnaks


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## SirDice (Sep 24, 2012)

m69 said:
			
		

> Is there any service or option that show me when the other side's interface is up?


ping(8)


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## m69 (Sep 24, 2012)

Thanks for your quick reply, I have an other question, If two systems can't ping each other because of firewall or other reasons what should I do to know the status of the other connection side?
Thanks


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## SirDice (Sep 24, 2012)

m69 said:
			
		

> Thanks for your quick reply, I have an other question, If two systems can't ping each other because of firewall or other reasons what should I do to know the status of the other connection side?


You simply can't tell.


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## gkontos (Sep 24, 2012)

m69 said:
			
		

> Thanks for your quick reply, I have an other question, If two systems can't ping each other because of firewall or other reasons what should I do to know the status of the other connection side?
> Thanks



ICMP (4)() and ICMP6 (4)() are being used as a first step to monitor network reachability. Therefore, intermediate firewalls have to be adjusted to permit those packets.


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## Uniballer (Sep 24, 2012)

You could certainly create your own "link is up" feature on a new or existing TCP or UDP application.  But it may be difficult to get real-time status using TCP, especially if the link is experiencing intermittent routing problems.  And UDP might become problematic when/if your links are congested.  And you certainly don't want to waste a lot of bandwidth etc. just finding out if the link is still up.  The best you can probably do is to know that you probed for connectivity 10 times in the last 5 minutes and 9 out of 10 probes were successful.


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## Morte (Sep 24, 2012)

if ICMP is blocked, and you're interested in a particular port, nc() can tell you useful information (nmap is a more advanced alternative).

```
nc -zv 127.0.0.1 25
```


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