Comcast (xfinitiy) Arris modem link light blinks orange (yellow?) rather than green - check your ethernet cable.

[jump to the update on this one, it’s not what I thought it was…]

When I switched from CenturyLink to Comcast two months ago my “boost” speeds were 50 up and 10 down on a rented Arris modem. The modem lights were green and i thought the link light was blinking green.

Recently comcast claimed to have doubled my internet speed. It did go up briefly to 100+ mbps, but now it’s back down again. Around the same time I noticed my modem link light started blinking yellow/orange.

It sounds like this may be associated with a > 100 mbps connection, but I suspect it also happens when there’s something amiss with Comcast’s network. Based on what I read and a call to Comcast there’s nothing to do about it as long as you’re getting the speed you paid for (which may not be the speed comcast promised, but there you go.) The comcast rep did say my area was suffering from network issues.

Update: A better thread on Amazon (!) says: "The light is orange when connected to a 100 Mbit device, and blue when connected to a 1 Gbit device”. My modem is connected to a GB device though (Airport Extreme), and the link light should be for upstream connection, not downstream. I may try a different ethernet cable...

Update b: I’m surprised, it’s not at all what I thought. The link light isn’t for upstream connections, it indicates downstream (internal) connection mode — 10/100 is yellow/amber/orange, 1000 (gb) is green. I’d forgotten that, in the midst of resolving an issue with a dying time capsule, I swapped out the ethernet cable connecting my Comcast modem to my Airport extreme. The new cable was a better length, and I thought it was excellent quality. Turns out it wasn’t so excellent! I swapped my original cable back in and the light immediately went green.

I then repeated the Comcast speed test, this time with my Macbook Air within a few feet of my router. For convenience I tried with 5GHz Wifi, not wired gb ethernet. Comcast more than passed the speed test — delivering 125 mbps over wifi. I don’t know if my modem reports a faster internal speed to Comcast and if that impacts provisioning. I’m used to berating my ISP, but Comcast did very well on this one. With 100+mbps (much less gbps) broadband internal networks matter.

In the dining room, a floor below and about 20’ feet away, the same speedtest over 5GHz wifi gave me about 73 mbps (my 11” Air might have been a wee bit faster than my 13” Air). Quite an impressive reduction.