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Thread: : arp tables
www.piclist.com/techref/mems.htm?key=table
face picon face BY : Justin Richards email (remove spam text)



Hi Folks,

my understanding of arp tables is that when a layer 3 packet is
destined for a given ip an arp request is sent out the adapter.

The arp request is in the form of 'who has ip 192.168.0.1'.  If that
host 192.168.0.1 is on the network segment then it will reply with its
mac address.  This is then added to the arp table and the packet is
encapsulated with the layer 2 frame with the destination mac it just
learnt.

If the destination host is via a router then the router will respond
with its mac address and the packet is encapsulated with that mac
address and the router takes care of it.

This appears to agree with the info when googled.

I am experincing conflicting results on what appears to be identicle
setups as follows:-

1. Any destination ip address handled by the gateway device does NOT
result in an arp entry but all local ip address are added.
2. Any destination ip address handled by the gateway device does
result in an arp entry but all local ip address are added.

Perhaps this should not go to the piclist, but all the info I have
gathered from the web is that there should be an individual arp entry
for each ip address.

Any explaination as to why a setup would behave one way or the other.

Platforms
2 x TRU64 on Alpha1400's where i get both results
1 x XP profession where I dont get an entry for remote hosts.

I am using pings to test and I know there are connections to other remote hosts.

Cheers Justin
<9c638c4a0808200400j27952be1kb09c7fdeb6c6db8b@mail.gmail.com> 7bit

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