Date: Mon, 4 Dec 2006 19:20:11 +0100 From: Jona Joachim <jona.joachim@free.fr> To: a@zeos.net Cc: freebsd-questions@freebsd.org Subject: Re: How does my computer work with an empty arp table? Message-ID: <20061204192011.430c3352@localhost> In-Reply-To: <20061204061444.GA653@host.my.domain> References: <20061203174849.GA4561@host.my.domain> <df9ac37c0612031453s31f91172wd07dc3a9c8e571b0@mail.gmail.com> <20061204061444.GA653@host.my.domain>
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On Mon, 4 Dec 2006 08:14:44 +0200 a@zeos.net wrote: > On Sun, Dec 03, 2006 at 02:53:44PM -0800, Atom Powers wrote: > > On 12/3/06, a@zeos.net <a@zeos.net> wrote: > > >My computer is connected to ISP via ADSL and works properly. > > > > > >I typed > > > > > >arp -a > > > > > >and saw an empty table, although I pinged successfully an Internet > > >host one second ago. > > > > The ARP table is a cache of known ARP<->IP addresses. If there are > > no addresses in the ARP table then the system will send out an ARP > > broadcast to discover the ARP address that belongs to the IP > > address. Of course only the Ethernet hosts on your local network > > will be in your ARP table. > > > > -- > > -- > > Perfection is just a word I use occasionally with mustard. > > --Atom Ray Powers-- > > Thank you for response. > > But why there is no MAC address of my ADSL modem connected via > Ethernet? Does my host send broadcast frames to communicate with > modem everytime? > > Furthermore, when I ping the modem, a proper entry appears in table: > > ------------------------------------------------------------------------ > $arp -a > > $ping -c 1 rt # It is my modem > PING rt.my.domain (192.168.1.1): 56 data bytes > 64 bytes from 192.168.1.1: icmp_seq=0 ttl=254 time=1.298 ms > > --- rt.my.domain ping statistics --- > 1 packets transmitted, 1 packets received, 0% packet loss > round-trip min/avg/max/stddev = 1.298/1.298/1.298/0.000 ms > > $arp -a > rt.my.domain (192.168.1.1) at 00:13:49:61:f9:b2 on rl0 [ethernet] > ------------------------------------------------------------------------ > > But no entry appears when I communicate trough the modem. Perhaps your modem works as a transparent bridge. Jona
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