[Xorp-users] VLAN Interfaces

[Ray Soucy]

I'm not really sure what the best way to address VLAN support in XORP
is.  It's definately broken and it breaks more than just the ability
to create a VLAN interface from XORP.

In its current design, for a port with one VLAN and no untagged
interface address, it should look like:

   interface eth0 {
        description: "Trunk Port"
        disable: false
        discard: false
        unreachable: false
        management: false
        vif eth0 {
            disable: false
        }
        vif "eth0.2" {
            disable: false
            vlan-id: 2
            address 192.168.0.1 {
                prefix-length: 24
                disable: false
            }
        }
    }

This would create the sub-interface from XORP.  Or you could import
interfaces created outside of XORP:

   interface eth0 {
        description: "Trunk Port"
        disable: false
        discard: false
        unreachable: false
        management: false
        default-system-config {
        }
    }

This is not the case.

The solution many have discovered, is to create the VLAN interface
outside of XORP, then configure it as a physical interface in XORP.
One would expect that this would look like this:

   interface "eth0.2" {
        description: "VLAN 2"
        disable: false
        discard: false
        unreachable: false
        management: false
        default-system-config {
        }
    }

Unfortinately it doesn't seem to.  My guess is that
"default-system-config" can only be applied to a physical interface.

This would be fine, if using "default-system-config" on the parent
interface would also import sub-interfaces (which I believe was the
intent of how it would work), but that is certainly broken.

In addition, if you use "default-system-config" on a parent interface,
but explicitly deinfe a sub-interface, that will break XORP interface
indexing as well.

In its current state the only way to get around this is to explicitly
define the IP address of any interface using VLAN's and define all
VLAN sub-interfaces as if they were physical interfaces (even if you
don't give the untagged interface an address):

   interface eth0 {
        description: "Trunk Port"
        disable: false
        discard: false
        unreachable: false
        management: false
        vif eth0 {
            disable: false
        }
   }
   interface "eth0.2" {
        description: "VLAN 2"
        disable: false
        discard: false
        unreachable: false
        management: false
        vif "eth0.2" {
            disable: false
            address 192.168.0.1 {
                prefix-length: 24
                disable: false
            }
        }
    }

While you could change XORP to better support defining VLAN interfaces
as if they were physical interfaces rather than VIF's, I think this
would ultimately break more of XORP (because everything seems to be
designed around this concept of how interfaces are represented) and
ultimately be more work than trying to fix the original design.

Either way, I think the documentation might need to be updated to
reflect the current state of VLAN support so we see less frustration
towards XORP and perhaps more community support.

On Tue, Feb 15, 2011 at 3:25 PM, Joe Coco <jcoco at meccorp.mec.edu> wrote:
>> Yes, but the interface will not be admin up, and all sorts of code will not
>> actually function properly.
>
> How do you tell if it is 'admin up' ?
>
> The hack I wrote, seems to make it work although I have not tested much more than basic pinging.
>
> xorp at asterisk# show interfaces interface eth1
>    description: "Eth1"
>    vif "eth1.100" {
>        vlan {
>            vlan-id: 100
>        }
>        address 1.1.1.1 {
>            prefix-length: 24
>        }
>    }
>    vif "eth2.100" {
>        vlan {
>            vlan-id: 200
>        }
>        address 2.1.1.1 {
>            prefix-length: 24
>        }
>    }
>
> [edit]
> xorp at asterisk#
>
>
>> I remain convinced that making the vlans a normal interface in the config file
>> (and xorpsh), and adding some vlan-id and parent-dev fields so that we can
>> create them properly is the way to actually get this working.
>
>>This would still be a decent amount of work...
>
> Probably. ZebOS does this kind of. You set switchport access under the physical interface (which vlans can pass), but the actual
> 'vif' is a vlanvid device that is treated like a normal interface not attached to the physical. With this config for example, you can
> put eth1 and eth2 both in vlan5 in bridge mode.
>
> If we could do something as simple as:
>
> # create interface vlan 100 disable false
> # create interface vlan 100 physical eth1 mode trunk
> # create interface vlan 100 physical eth2 mode access
> # create interface vlan 100 bridge-id 1
> # create interface vlan 100 address 1.1.1.1 prefix-length 24
>
> Which would then create a vlan100 interface, I think that would work just fine.
> In the above example, it would be in trunk (tag) mode on eth1, but native access
> mode on eth2 with a bridge group of 1. This could be built on for q-in-q support, etc.
>
> -- Joe
>
>
>
>
> -- Joe
>
>
>
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-- 
Ray Soucy

Epic Communications Specialist

Phone: +1 (207) 561-3526

Networkmaine, a Unit of the University of Maine System
http://www.networkmaine.net/