At 05:33 PM 4/10/01, Chuck Larrieu wrote:
>Priscilla, does the routing protocol itself deal at the MAC layer? Or is
>that a function of the router hardware interface process?
Well, here's how I would say it. The routing protocol gives its packet to
the network layer which hands the packet to the software driver for the
interface. Somewhere in the middle of the network layer and the MAC layer
the software converts the destination broadcast or multicast appropriately.
255.255.255.255 and 0.0.0.0 probably always get converted to
FF:FF:FF:FF:FF:FF on Ethernet. IPX broadcasts probably always get converted
to all Fs too. AppleTalk never broadcasts, so the driver must be smart
enough to send to the AppleTalk multicast 09:00:07:FF:FF:FF. Finally, the
driver must also be smart enough to convert IP multicasts used by RIPv2,
EIGRP, and OSPF to the proper data-link layer multicast, using the
algorithm in RFC 988 ("Host Extensions for IP Multicasting.")
Another way to look at it is that the routing protocol specifications don't
specify the MAC destination address, which I think is what you are getting
at. The IGRP Rutgers document just says send to broadcast. The OSPF RFCs
just say the IP multicast destination. The IPX RIP document just says to
broadcast. Inside AppleTalk says to broadcast (even though it really uses
multicasts.)
Where do you put ARP? This is an analogous question, I think? Please let's
not really discuss that though. ;-)
Priscilla
>Chuck
>
>-----Original Message-----
>From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of
>Priscilla Oppenheimer
>Sent: Tuesday, April 10, 2001 6:25 PM
>To: [EMAIL PROTECTED]
>Subject: Re: Broadcast [7:132]
>
>At 07:38 PM 4/10/01, Hingchuen Chan wrote:
> >Hi guys,
> >
> >I read that distance vector routing protocols use the logical broadcast to
> >send its periodic update. What MAC address does it use then? Broadcast
too?
>
>Yes, broadcast or multicast.
>
>RIPv1 sends to IP destination 255.255.255.255 and Ethernet destination
>FF:FF:FF:FF:FF:FF. I have also seen RIP implementations that send to
>0.0.0.0 and implementations that send to network.0, (where the number of
>zeros depends on class), but all the implementations seem to send to
>FF:FF:FF:FF:FF:FF at the MAC layer.
>
>RIPv2 sends to IP destination 224.0.0.9 and Ethernet destination
>01:00:5E:00:00:09.
>
>Novell IPX RIP sends to IPX destination network.FF:FF:FF:FF:FF:FF and
>Ethernet destination FF:FF:FF:FF:FF:FF.
>
>RTMP sends to DDP destination network.255 and Ethernet destination
>09:00:07:FF:FF:FF.
>
>IGRP sends to IP destination 255.255.255.255 and Ethernet destination
>FF:FF:FF:FF:FF:FF.
>
>EIGRP sends hellos to IP Destination 224.0.0.10 and Ethernet destination
>01:00:5E:00:00:0A.
>
>With OSPF, though not distance vector and not what you asked about, Hello
>packets are sent to the multicast destination AllSPFRouters. The Designated
>Router and its Backup send both Link State Update Packets and Link State
>Acknowledgment Packets to the multicast address AllSPFRouters, while all
>other routers send both their Link State Update and Link State
>Acknowledgment Packets to the multicast address AllDRouters.
>
>AllSPFRouters is 224.0.0.5 and 01:00:5E:00:00:05.
>
>AllDRouters is 224.0.0.6 and 01:00:5E:00:00:06.
>
> >Also, would the recipient of the periodic update send it out again because
> >it is a logical broadcast?
>
>If the recipient were a switch or bridge, yes. Otherwise, no.
>
>Priscilla
>
>
> >Thanks in advance.
> >
> >
> >Hing
> >_________________________________________________________________________
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>
>________________________
>
>Priscilla Oppenheimer
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