Re: ARP cache entry for router
Re: ARP cache entry for router
- Subject: Re: ARP cache entry for router
- From: "Duane Murphy" <email@hidden>
- Date: Thu, 6 Nov 2003 08:44:34 -0800
--- At Wed, 5 Nov 2003 18:44:03 -0800, Ryan McGann wrote:
>
Short question: When we receive a notification from SystemConfiguration
>
that the default route has changed, I want to get the link layer
>
information for the router if applicable. From what I can tell, an ARP
>
entry always exists for the router, and I'm assuming it's added by the
>
kernel when the route is added. But can there be a case when this will
>
not be true? In other words, should I go to the trouble of crafting an
>
ARP packet and waiting for the reply, or is it a "99% safe" assumption
>
that the ARP entry will exist (assuming the router information is correct
>
in the user's settings)?
I cant tell you if the router will always be in the arp table. It kind of
makes sense to me, but there may be other cases.
What I can tell you is that listenting for ARP packets is not obvious.
You cannot just use a raw ethernet socket. You have to use a bpf filter
in order to listen for ARP.
...Duane
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