On 9 October 2014 22:01, Owen DeLong <[email protected]> wrote: > > Why do people assign addresses to point-to-point links at all? You can > just > > use a host /128 route to the loopback address of the peer. Saves you the > > hassle of coming up with new addresses for every link. Same trick works > for > > IPv4 too. > > > > Regards, > > > > Baldur > > <SARCASM> > > And it makes your trace-routes across parallel links oh so easy to > identify which of them is at fault for the packet loss, too. > > </SARCASM> >
There are a ton of other technologies with the same problem. Do you never use link aggregation? My "parallel links" are all link aggregations, so I would not have a way to identify links by traceroute anyway. There are a number of good technical reasons to want distinct addresses on > point to point links. > I am sure there are. Tell me about them. I am not disputing that there are many reasons to sometimes use link addresses. My question is why do you do it by default? So far we have heard two arguments: 1) You can ping the link address. I assume his equipment will down the address if the link is down. My equipment does not do this, I can ping it as long it is administrative up no matter link status. So this test is useless to me. I am monitoring links by SNMP anyway. 2) Parallel links. I don't have many of those, and the ones I have are link aggregations. MPLS interferes with this too. On the other hand not using link addresses has some advantages: 1) You don't need to assign and document them. 2) It is easy to think about: Router A talks to Router B on link AB. Every router has only one address so you don't need to remember which address to use. 3) You avoid having a lot of addresses configured on your router. 4) You are immune to all the NDP attacks. 5) You are immune to the monthly NANOG debate about using /127 vs /126 vs /124 vs /64. The correct answer is clearly use /128 :-). Regards, Baldur
