the pointtopoint flag is something typical for the medium used. E.g. ethernet is by nature a broadcast medium and thus not pointtopoint. PPP, as its name says,is a point to point protocol. So this is (or should be) not configurable, unless you are trying some weird setups. Guy mike stjohn wrote:> how do you set the pointopoint flag using ip command? > > is it an automatic setting when ip is configuring a ppp link | or am I > missing something in the ip-cref. > > > thanks > > msj > > > _______________________________________________ > LARTC mailing list / LARTC@mailman.ds9a.nl > http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://ds9a.nl/2.4Routing/
how do you set the pointopoint flag using ip command? is it an automatic setting when ip is configuring a ppp link | or am I missing something in the ip-cref. thanks msj
On Thu, Mar 22, 2001 at 11:20:00PM +0100, Guy Van Den Bergh wrote:> the pointtopoint flag is something typical for the medium used. > E.g. ethernet is by nature a broadcast medium and thus not pointtopoint. > PPP, as its name says,is a point to point protocol. So this is (or > should be) not configurable, unless you are trying some weird setups.You CAN use Ethernet in a point-to-point configuration, by the way. Saves some IP adresses. Regards, bert -- http://www.PowerDNS.com Versatile DNS Services Trilab The Technology People ''SYN! .. SYN|ACK! .. ACK!'' - the mating call of the internet
bert hubert wrote:> > You CAN use Ethernet in a point-to-point configuration, by the way. Saves > some IP adresses. >How do you that? PPPoE (PPP over Ethernet)? This is more like ppp emulation over ethernet. And thus this introduces protocol overhead. What do you mean by this? I''m puzzled. Guy
bert hubert wrote:> On Sun, Mar 25, 2001 at 08:07:48PM +0200, Guy Van Den Bergh wrote: > > >>> You CAN use Ethernet in a point-to-point configuration, by the way. Saves >>> some IP adresses. >> >> How do you that? PPPoE (PPP over Ethernet)? This is more like ppp >> emulation over ethernet. And thus this introduces protocol overhead. >> >> What do you mean by this? I''m puzzled. > > > It''s still ethernet. But instead of assigning a /30 with 4 IP addresses, you > just route to your device. Not rocket science, just saves IP addresses. > > Regards, > > bert hubertBut you require the next hop to do proxy arp if you would like this to work! And certainly this is not a point-to-point configuration of ethernet. If you route to your device instead of your nexthop the kernel is going to send an arp request for de destination address, and if the destination is not on the lan, some router on the lan has to do proxy arp on behalf of the destination. Otherwise your packets will be dropped. The kernel still thinks the lan is a broadcast medium. I believe this is a lot more complicated than "just routing to your device"! Even if you have a crossconnect cable between two hosts or routers, the medium inbetween is still broadcast and not point-to-point. I know this discussion is going way too far into semantics, but as far as I know there is no such thing as point-to-point mode of ethernet. Guy
On Sun, Mar 25, 2001 at 08:07:48PM +0200, Guy Van Den Bergh wrote:> > You CAN use Ethernet in a point-to-point configuration, by the way. Saves > > some IP adresses. > > How do you that? PPPoE (PPP over Ethernet)? This is more like ppp > emulation over ethernet. And thus this introduces protocol overhead. > > What do you mean by this? I''m puzzled.It''s still ethernet. But instead of assigning a /30 with 4 IP addresses, you just route to your device. Not rocket science, just saves IP addresses. Regards, bert hubert -- http://www.PowerDNS.com Versatile DNS Services Trilab The Technology People ''SYN! .. SYN|ACK! .. ACK!'' - the mating call of the internet
On Sun, Mar 25, 2001 at 09:29:30PM +0200, Guy Van Den Bergh wrote:> But you require the next hop to do proxy arp if you would like this to work! > And certainly this is not a point-to-point configuration of ethernet. If you route to your device instead of your nexthop > the kernel is going to send an arp request for de destination address, and if the destination is not on the lan, > some router on the lan has to do proxy arp on behalf of the destination. Otherwise your packets will be dropped. > The kernel still thinks the lan is a broadcast medium. > > I believe this is a lot more complicated than "just routing to your device"! > > Even if you have a crossconnect cable between two hosts or routers, the medium inbetween is still broadcast and not > point-to-point. > > I know this discussion is going way too far into semantics, but as far as I know there is no such thing as point-to-point mode of ethernet.You can disable arp and set static arp entries. Do that, plus a crossover cable and full-duplex, and I''d have a very hard time calling your ethernet anything but point-to-point. :)
Gregory Maxwell wrote:> On Sun, Mar 25, 2001 at 09:29:30PM +0200, Guy Van Den Bergh wrote: > >> >> Even if you have a crossconnect cable between two hosts or routers, the medium inbetween is still broadcast and not >> point-to-point. >> >> I know this discussion is going way too far into semantics, but as far as I know there is no such thing as point-to-point mode of ethernet. > > > You can disable arp and set static arp entries. Do that, plus a crossover cable > and full-duplex, and I''d have a very hard time calling your ethernet > anything but point-to-point. :)The point was that it is a lot more complex than simply adding a route to the device instead of to the nexthop. Let''s remember that ethernet is by nature a broadcast medium and if you want it to behave like a point-to-point link you will have to be careful. Adding static arp entries has some drawbacks which you do not have on real point-to-point links. In the end you are still trying to let a broadcast medium behave like a point-to-point link. Nothing more and nothing less. Guy