External Layer2 Concentrator support

This feature is available from Release 1.0.1 onwards and applicaple when Layer 2 bridging is enabled.

Adding and removing Layer2 GRE headers puts processing overhead on the POP radio. External Concentrator could be a Linux server or any router/ switch supporting IPv6 L2GRE tunnels. eg Juniper MX 100 or router which support Layer 2 GREv6 tunneling . It can also be a POP node in the mesh.Make sure to setup MTU size as 1986 (atleast 1600) on all switches between POP and Tunnel Endpoint. This configuration is present in Network Configuration and is applicable to all the nodes of that site.

Enter IPv6 address of Tunnel Concentrator in Static.

Under Network Configuration.
Select ‘Static’ Tunnel concentrator option and configure external concentrator IPv6 address.


Ubuntu Script for L2 GRE Tunnel
gre.txt (1.2 KB)


4 posts were split to a new topic: When will external layer 2 concentrator support be available

A post was split to a new topic: System requirements for External Layer 2 Concentrator

How many tunnels will work without having to use an external concentrator? If this value is low then we will go ahead with an external concentrator from the start. Thanks.

Number of tunnels is not the limitation, but the PPS/throughput.
With POP using single sector, there is no issue.
With both sectors at MCS12 and bidirectional traffic, 20% throughput reduction is seen with onboard concentrator. In Q4 release, We will be moving to a different datapath architecture implementation called Vector Packet Processing (VPP), we expect to bridge this gap significantly.
We recommend to start with POP as concentrator.


Hello @Kiran_Avva

I have a challenge with a v5000 onboard controller as layer2 is enabled but it shows 0tunnel as seen attached. Hence no traffic on the v1k

kindly assist.

Are you using external concentrator ? Can you please collect field diags and send. The file will be about ~20 MB. You can upload somewhere and DM the link to me.

Thank you for your response.

I have been able to resolve the issue. I forgot to check the pop node box.

do you support Cisco ASR 9k as a concentrator?

When we checked an year back, there was no IPv6 Layer 2 GRE support in Cisco ASR 9K. IPv4 L2GRE and IPv6 Layer 3 GRE was present.

Please check if IPv6 Layer 2 GRE is available in latest SW version of Cisco.

Did anyone ever find out if Cisco added IPv6 L2 GRE?

Can you confirm if the V3000 has the same processing capacity to act as a POP (and tunnel endpoint) as the V5000? We have a couple of cases where the POP node will be a V3000, as point to point link from our fibre to a DN site, and I just wanted to be sure this would not impose any particular capacity issues instead of using a V5000 as the POP node. Thanks.

The V3000 is capable of acting as a POP and terminating the tunnels. In theory it has even more processing capacity then the V5000.

The use of the V3000 either acting as a PTP and relay to the V5000 or directly to the V5000 DN-DN is a nice solution to inject the POP capacity in to the distributed network.