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iw-interfaces and stitching pseudowires

[ Edited ]
‎04-29-2009 05:16 AM

Hi,

I need some guidance to understand a given configuration:

 

There is a configuration for pseudowire emulation with juniper mx960 up and running in our lab. This mx960 is working as a switching pe to connect to devices, oncee with martini-signaling, the other with kompella-signaling.

 

Could you explain the usage of iw-interfaces in this context to me, please?

Is it correct, that this interfaces switch and stitch the pseudowires? Could you explain that please (or maybe give me a helpful link)?

 

Do I need the part "site sitename {....}"  if there is no multi-homing? 

 

Some parts of our config is posted below, maybe this is helpful for understanding. 

 

Thanks,

Christian 


 

iw0 {

        description iw-l2vpn-l2ckt;

        }

        unit 50 {

            encapsulation vlan-ccc;

            vlan-id 1000;

            peer-unit 51;

        }

        unit 51 {

            encapsulation vlan-ccc;

            vlan-id 1000;

            peer-unit 50;

        }

}

 

 

l2circuit {

        neighbor XX.XX.XX.XXX {

            interface iw0.51 {

                virtual-circuit-id 2005;

                description eline5-l2ckt;

                no-control-word;

                mtu 8990;

            }

        }

 

 

eline5-l2vpn {

        instance-type l2vpn;

        interface iw0.50;

        route-distinguisher XXXXX:1051000;

        vrf-target target:XXXXX:1051000;

        protocols {

            l2vpn {

                encapsulation-type ethernet-vlan;

                no-control-word;

                site sitename {

                    site-identifier 2;

                    site-preference primary;

                    interface iw0.50 {

                        remote-site-id 1;

                    }

                }

                mtu 8990;

            }

        }

Message Edited by bookweb on 04-29-2009 06:26 AM
2 REPLIES 2
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Re: iw-interfaces and stitching pseudowires

‎04-30-2009 07:13 PM

Christian,

 

This is a relatively new feature in JUNOS 9.3.  As far as I can tell, it basically implements a "stitch" of two pseudowires which have their inner label derived through different control plane mechanisms.

 

According to the information I've seen, it looks like the iw0 interface is really a control plane construct that's used to program the hardware to do an inner-label and outer-label swap on traffic between two pseudowires.

 

So, the good news is that this allows the stitching of the pseudowires straight-through the ASICs, without having to use a tunnel services interface (as was previously required before this feature).  Since it's effectively not terminating each pseudowire at dataplane, the encapsulation types must match.  It is literally just doing the label swaps to push traffic from one PW to another.

 

Since the martini l2circuit is using targeted LDP to exchange the inner label based on the VC-id, the ID must match on both sides of the martini tunnel.  In the L2VPN, the routing-instance uses the Kompella algorithm to automatically calculate the inner label from the label base and offset, so it will require you to include the site-id (which is used to advertise the offset to remote peers).  Even if the L2VPN has only two remote sites, it will normally require the site-ID.

Dan Backman
JNCIE-ER #6 / JNCIE-M #265 / JNCI
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Re: iw-interfaces and stitching pseudowires

‎01-06-2014 03:00 AM
Detail the HW resources involved to implement the PW-HE functionality. Assume that the PE equipment has 2 MPLS core links in different line cards. Detail the impact on the PW-HE and describe what happens in terms of HW resources involved in the PW-HE termination the impact of the following failures:
- Core link failure
- Line card failure
- Route Processor failure
- Switch Fabric failure
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