Network Technical Specifications


Ports, IPv4 and IPv6

All ports on the LU-CIX public exchange infrastructure are Ethernet and are available at the following speeds:

  • 1 Gbps (GE) - 1000BASE-LX
  • 10 Gbps (10GE) - 10GBASE-LR
  • 100 Gbps (100GE) – 100GBASE-LR4

Additionally, LU-CIX is able to aggregate GE, 10GE or 100GE ports to provide higher bandwidth trunks.

Members can peer with IPv4, IPv6 or both. LU-CIX strongly recommends peering with both IPv4 and IPv6 address families.


MAC Layer

Ethernet framing

The LU-CIX infrastructure is based on the Ethernet II (or “DIX Ethernet”) standard. This means that LLC/SNAP encapsulation (802.2) is not permitted.


Frames forwarded to LU-CIX ports must have one of the following Ether types:

  • 0x0800 - IPv4
  • 0x0806 - ARP
  • 0x86dd - IPv6

One MAC address per port

Frames forwarded to an individual LU-CIX port shall all have the same source MAC address.

No proxy ARP

Use of proxy ARP on the router's interface to the Exchange is not allowed.

Unicast only

Frames forwarded to LU-CIX ports shall not be addressed to a multicast or broadcast MAC destination address except as follows:

  • broadcast ARP packets
  • multicast ICMPv6 Neighbour Discovery packets. This DOES NOT include Router Discovery packets.
  • multicast is only allowed on the separated Multicast VLAN

No link-local traffic

Traffic for link-local protocols shall not be forwarded to LU-CIX ports.
Link-local protocols include, but are not limited to, the following list:

  • IRDP
  • ICMP redirects
  • IEEE 802 Spanning Tree
  • Vendor proprietary protocols. These include, but are not limited to:
    - Discovery protocols: CDP, EDP - VLAN/trunking protocols: VTP, DTP
    Interior routing protocol broadcasts (e.g. OSPF, ISIS, IGRP, EIGRP)
  • PIM-SM
  • PIM-DM
  • ICMPv6 ND-RA
  • UDLD
  • L2 Keepalives

The following link-local protocols are exceptions and are allowed:

  • ARP
  • IPv6 ND


BFD (Bidirectional Forwarding Detection)

LU-CIX recommends configuring BFD as a failure detection mechanism on all BGP peering sessions, be it peer-to-peer or with the route servers.

BFD is a generic keepalive and failure detection protocol that runs over almost any communication media. It allows sub-second failure detection, if participating systems are fast enough. It is designed as a lightweight protocol that can run autonomously in the forwarding engine of network devices, independent of the control plane.

In our case, BFD can be configured as an additional failure detection mechanism for BGP. Each BGP session will be doubled by a dedicated BFD session that runs on UDP ports 3784 and 3785, on the same IPv4 or IPv6 addresses as the BGP session itself. When BFD detects the failure of a neighbor, it informs the BGP process which triggers immediately the withdrawal of the neighbor’s routes, shortcutting the overly generous BGP timeouts and enabling the immediate use of an alternate route.

On LU-CIX, we now encourage members to use BFD on their peer-to-peer peering sessions. This allows for extremely fast failover in case of data path outages for whatever reason. In addition, we will start offering BFD support on the route servers. Thus, BGP sessions with the route servers can also be protected with BFD.

The following are our current recommended timer values for BFD:

  • Min Rx interval     300ms
  • Min Tx interval     300ms
  • Idle TX interval    1000ms
  • Multiplier              3

These are preliminary values that we use on the route servers. If you are interested to trial BFD on the route servers with us, please contact us at support[at]lu-cix[dot]lu. We are looking for testers!