[Xorp-users] Virtual interfaces in GNU/Linux

[Pavlin Radoslavov]

Pepo <pmancheno at gmail.com> wrote:

> El Domingo, 17 de Diciembre de 2006 11:50, escribió:
> > > I am trying with Xorp for my multicast thesis and looks terrific :) my
> > > tests were using (just one) Debian Etch box and Qemu so I had a virtual
> > > network just like the image attached; but now I have to show my tests in
> > > a real network.
> > >
> > > For my real-test I will use normal computers and some others as routers
> > > with Xorp, but I have just one NIC in each PC, so, How do I can use
> > > virtual interfaces just like in a normal GNU/Linux.
> > >
> > > 	ifconfig ethN:X <address>
> > > 	(ifconfig eth0:1 192.168.1.1)
> >
> > First, you need to configure manually the virtual interfaces; i.e.,
> > in advance before starting XORP (in the future XORP should have
> > support for configuring virtual interfaces).
> >
> > Then, inside the XORP configuration you use the virtual interfaces
> > as any other (physical) interface. For example, if the interface
> > names shown by "ifconfig -a" are eth0:1 and eth0:2, then your
> > configuration might look like the one below.
> > Though, double-check that eth0:1 and eth0:2 are indeed configured
> > with IP addresses, they are multicast capable (the MULTICAST flag is
> > set), and are UP.
> >
> > Please let us know if this setup is not working properly.
> >
> > Regards,
> > Pavlin
> >
> > ================================================================
> >
> > interfaces {
> >     interface eth0:1 {
> >         default-system-config
> >     }
> >     interface eth0:2 {
> >         default-system-config
> >     }
> > }
> >
> > plumbing {
> >     mfea4 {
> >         interface eth0:1 {
> >             vif eth0:1 {
> >                 disable: false
> >             }
> >         }
> >         interface eth0:2 {
> >             vif eth0:2 {
> >                 disable: false
> >             }
> >         }
> >         interface register_vif {
> >             vif register_vif {
> >                 disable: false
> >             }
> >         }
> >     }
> > }
> >
> > protocols {
> >     igmp {
> >         interface eth0:1 {
> >             vif eth0:1 {
> >                 disable: false
> >             }
> >         }
> >         interface eth0:2 {
> >             vif eth0:2 {
> >                 disable: false
> >             }
> >         }
> >     }
> >
> >     pimsm4 {
> >         interface eth0:1 {
> >             vif eth0:1 {
> >                 disable: false
> >             }
> >         }
> >         interface eth0:2 {
> >             vif eth0:2 {
> >                 disable: false
> >             }
> >         }
> >         interface register_vif {
> >             vif register_vif {
> >                 disable: false
> >             }
> >         }
> >
> > 	static-rps {
> > 	    rp 10.0.0.1 {
> > 		group-prefix 224.0.0.0/4 {
> > 		}
> > 	    }
> > 	}
> >     }
> >
> >     fib2mrib {
> >         disable: false
> >     }
> > }
> >
> > ================================================================
> 
> What if I use:
> 
> interfaces {
> 	interface eth1 {
> 		disable: false
> 		vif eth1 {
> 			disable: false
> 			address 192.168.1.10 {
> 				prefix-length: 24
> 				broadcast: 192.168.1.255
> 				disable: false
> 			}
> 			address 192.168.13.1 {
> 				prefix-length: 24
> 				broadcast: 192.168.13.255
> 				disable: false
> 			}
> 		}
> 	}
> }
> 
> plumbing {
> 	mfea4 {
> 		disable: false
> 		interface eth1 {
> 			vif eth1 {
> 				disable: false
> 			}
> 		}
> 		interface register_vif {
> 			vif register_vif {
> 				disable: false
> 			}
> 		}
> 	}
> }
> 
> protocols {
> 	igmp {
> 		disable: false
> 		interface eth1 {
> 			vif eth1 {
> 				disable: false
> 			}
> 		}
> 	}
> 	pimsm4 {
> 		disable: false
> 		interface eth1 {
> 			vif eth1 {
> 				disable: true
> 			}
> 		}
> 		interface register_vif {
> 			vif register_vif {
> 				disable: false
> 			}
> 		}
> 		bootstrap {
> 			disable: false
> 			cand-bsr {
> 				scope-zone 224.0.0.0/4 {
> 					cand-bsr-by-vif-name: "eth1"
> 				}
> 			}
> 		}
> 	}
> }
> 
> I mean just using differents IPs in the same NIC --> Do it works? efficient?
> 
> In my virtual test I have a PC with 4 NICs, I dont if using 4 IPs is the same 
> (efficient) of 4 NICs.

Yes, the above setup is correct (modulo the fact you are missing the
fib2mrib configuration), but you should have in mind that
you actually have a single network interface with two IP
addresses, and this is different from having virtual interfaces
(your original question).

Futhermore, you cannot perform multicast routing between two IP
addresses that belong to the same network interface, otherwise the
multicast data packets will start looping.

Pavlin