Re: arp who-has? tell?

[John Cornelius <jc@xxxxxxx>]

Actually, these messages are coming from the DHCP server for the physical segment (not subnet) that the modem is on. It's updating its tables of active addresses so that it can put inactive ones back into the mix for subsequent allocation to other sites. The 98.203.0.1 address is the address of the DHCP server.

ARP requests are done at the network's physical layer because interfaces are not guaranteed to have an IP address so while subnet masks don't effect them physical segmentation does.

It's pretty normal for cable internet providers to do this to keep their tables up to date. They can also have more than one network on a physical segment which might explain the "strange" addresses.

Finally, all interfaces will generate ARP requests because when you try to make a connection to an IP address on the same subnet you don't know what its physical address is so your computer issues an ARP request of the form "who has nn.nn.nn.nn". Whoever has that address responds with its physical address and then you can make your connection. All ethernet communications is ultimately done between physical addresses which may explain why we go to all of this trouble.

--jc

Jacques B. wrote:

<snip>
  

I can see the 98.203.0.1 entries being potentially normal.  Depending
how they set things up, you could have an entire street or
neighbourhood on a subnet.  ARP requests are broadcast ARPs which
would be seen by all hosts on the subnet, so normal traffic.  I am at
a lost for explaining the ARP requests coming from other ranges of IPs
that are no doubt not in your subnet.  What is your subnet mask?  That
would help determine what broadcast traffic you should see.

Jacques B.

    

Further to my last message, what is your default gateway as well (I'm
guessing 93.203.0.1 but I shouldn't assume)?

Jacques B.

  

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