None

13 Jun 2026

      interfaces.  Suppose the following configuration for router A,

# ifconfig eth0 10.1.1.1 netmask 255.255.255.0 broadcast 10.1.1.255
# ifconfig eth1 10.2.2.2 netmask 255.255.255.0 broadcast 10.2.2.255
# ifconfig eth0:0 10.10.10.1 netmask 255.255.255.0 broadcast 10.10.10.255

and a similar one for another router B,

# ifconfig eth0 10.1.1.42 netmask 255.255.255.0 broadcast 10.1.1.255
# ifconfig eth1 10.3.3.42 netmask 255.255.255.0 broadcast 10.3.3.255
# ifconfig eth0:0 10.10.10.42 netmask 255.255.255.0 broadcast 10.10.10.255

and then for each say we set up OSPF on eth0:0 such as

protocol ospf {
  ...
  area 0.0.0.0 {
    interface "eth0:0" {
      cost 10;
      stub no;
      hello 10;
      ...
      type nonbroadcast;
      strict nonbroadcast yes;
      authentication none;
      neighbors {
        10.10.10.42 eligible;
      };
    };
    interface "eth1" {
      cost 10;
      stub yes;
      ...
    };
  };
}

If we check the configuration for ospf, we don't see interface eth0:0 at
all:

# birdc
BIRD 1.0.4 ready.
bird> show ospf interface
ospf1:
Interface "eth1":
	Area: 0.0.0.0 (0)
	Type: broadcast
...

and note the signifigant absence of eth0:0.

So apparently we can't route over alias interfaces?  Is there any
technical reason for this?  I'd really like to be able to because I have a
number of routers with different subnets hanging off of them, and some
routers beneath those subnets.  But I can only route over one particular
subnet per interface, the one assigned to the physical interface.

Thanks!
'james

-- 
James A. Crippen <james@unlambda.com> ,-./-.  Anchorage, Alaska,
Lambda Unlimited: Recursion 'R' Us   |  |/  | USA, 61.2069 N, 149.766 W,
Y = \f.(\x.f(xx)) (\x.f(xx))         |  |\  | Earth, Sol System,
Y(F) = F(Y(F))                        \_,-_/  Milky Way.