As of yesterday morning the Level 3 fibre is now live with customer traffic, and takes over the default routing previously had by Virgin Media.
We’ve also enabled our “floating default gateway”, based on Cisco’s GLBP (Gateway Load Balancing Protocol), which provides outbound load-balancing, and allows us to “flip” between Level 3 and BT.
As always when you get a new internet connection, the first thing you do is speed test it! We’ve not been able to find a UK server with enough bandwidth to fully test the 1Gbit link, the closest we could find was a server in London:
Customers may notice traffic coming in or going out of the Sheffield Data Centre via different paths, and perhaps not the path they were expecting. This is normal.
DrayTek routers and Cisco GLBP
We’ve found that DrayTek routers don’t seem to like the “floating” part of the load balancer. In basic terms, Cisco GLBP works by having a “master” ARP the MAC addresses of the “slave” routers to clients when they request the MAC of the default gateway to send traffic to. That way the gateway and MAC can be switched to the other router for failover, and the “master” can load-balance outbound traffic across the two links. DrayTek routers don’t seem to respond to the ARP request properly and never get the MAC address of the router.
We have a fix in place, and are working with affected customers. This only seems to affect customers with DrayTek hardware, all other routers, firewalls, and servers seem to be OK.