SUMMARY etherfind&arp

Date: Thu Feb 16 1995 - 16:38:04 CST


    could someone tell me where i can find the source code of
etherfind command of SUNOS4.1.3 ? or a program has same function?
i found it is useful when i do some checking.
    another question: i don't understand the arp command , when
i try arp <myhostname>, it said no entry. when i try arp -a ,i can
find some hosts' ethercard address ,but not all . should i do something?


From: MX%"" 10-FEB-1995 03:02:47.75

The arp cache only contains entries that your host has communicated with.
You will not have an entry for your localhost because it does not need
its own ethernet address to talk to itself over the network (it uses loopback).
If you want all hosts from the local network in the arp cache, simply ping
each host. (Keep in mind that the arp cache is temporary and will go
away when you reboot.)
To look up your own ethernet address, you can use the command dmesg to
display the system boot messages. Unless you have had many errors since
boot, you will see the ethernet address as one of the listings.

From: MX%"synacom!" 10-FEB-1995 03:06:23.10
You can find tcpdump at a site near you.

From: MX%"" 10-FEB-1995 03:50:47.34

ping first then arp.

From: MX%"" 10-FEB-1995 08:03:10.05

Etherfind is Sun source, and not available to my knowledge. You
can get the public domain snoop program though, which does a better
job anyway. archie should be able to tell you where to find it.

You don't need an entry for your machine, it never goes via the hardware.
The ARP cache is just that, a cache. If you haven't talked to a machine,
it won't be there, and entries age and are removed over time as well. Try
pinging a machine and then looking, it will be there.

From: MX%"" 10-FEB-1995 19:05:24.36

There's only something in the arp cache when you've had a
communication between the machines. Force something in there
with a ping first.
Or get the prog getethers which will do it all

From: MX%"" 10-FEB-1995 19:09:33.41

> another question: i don't understand the arp command , when
>i try arp <myhostname>, it said no entry.

That's because your machine doesn't need to know its own Ethernet address to
talk to itself.

>when i try arp -a ,i can find some hosts' ethercard address ,but not all .
should i do something?

ARP entries are added only when your machine communicates with another host,
so the hosts for which you can't find the addresses are ones with which
you've had no contact. Note that entries may not be permanent; they may only
be cached for a while.

The best way to force arp to add entries for all hosts on your subnet is to
send a broadcast to all hosts. Find your host's IP address and your netmask,
and turn it into a broadcast address:

<broadcast> = (<host address> AND <netmask>) OR (NOT <netmask>)

Then ping that address, and do an arp -a.

From: MX%"" 10-FEB-1995 19:30:34.55

 arp -a only gives you the adresses currently in cache.
 Try pinging to the broadcast adress: ping
 and then do arp -a. The should be all the machines in the local net.

PS: adresses stay in cache for a small time.

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