You can do a lot of these things without loopbacks but that requires you to implement kludges and hacks. Router / cluster IDs, iBGP peering backed by an IGP such as OSPF, PIM RPs, MSDP peering, tunnel sources and destinations, NAT sources, VRF targets / identifiers… the uses are a plenty. Most non-trivial routing protocol and NAT setups need loopback addresses for, well, many things, pretty much any network engineer will tell you that. Loopbacks are commonly used as traffic sources and destinations - software can listen on a loopback interface (like it does on 127.0.0.1). From a routing point of view this is important because a route to a loopback IP address will therefore always be active in the routing table. not bound to any NIC) which unless shutdown, are permanently in the "up" state. Some GUI functions don't support loopbacks (say GRE tunnels - you can't specify a loopback-based source of the tunnel), but you're OK using them in bgpd configs, to what loopback interfaces are: they are software-driven interfaces (i.e. Or make it an alias (secondary IP) for lo0. This has been mentioned in this forum before. To the OP: as suggested above, install the shellcmd package (if your platform allows package installation) and add the necessary "ifconfig lo1 create ifconfig lo0 up inet a.b.c.d 255.255.255.255" into early start commands. I think this should be raised as a feature request: allow the creation and control over loopback interfaces.
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