On 07.06.2016 12:46, Krishna Mohan wrote: > HI All, > I have a question to determine the uses of multiple loopbacks > interfaces(int loopback) in routing(quagga) on linux kernel. Please > apologise if it is a dumb question. This is what I understand, please > clarify if my understanding is correct. > > 1. we need them to represent a /32 ip, normally used for router-id. > 2. we can measure traffic destined to that ip, via its independent > statistics per loopback interface. > 3. ip unnumbered uses loopbacks to represent that ip. > > my question is, is it necessary to have ifindex per loopback interface > we create? if I create kernel loopback as lo:1 (as subinterface on > default loopback in kernel) with ip assigned to it will do 1. for > getting 2 and 3 done, loopback needs to be a separate netdev. is that > correct?
That is correct, you can terminate the ip addresses for iBGP (or router-id in this case) connections easily on any ip address that is bound to some interface within the kernel. Note, that you don't necessarily get the statistics correctly updated if you short-cut the packet internally in the kernel. So the statistics on the dummy or loopback device might not be accurate in such a setup. > Will I be having any advantage if I configure the interface as lo:1 vs > a separate netdev per loopback interface (i mean dummy netdev) to > terminate the /32 destined traffic? >From kernel PoV it doesn't matter. It is a question of taste and what your tools prefer. Bye, Hannes
