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Comment by zrail | Hacker News Reader

I just picked up a Mikrotik CRS305 from Amazon and a pair of used Intel X520T dual SPF+ cards from eBay, plus a couple DAC (direct attach copper) cables for maybe $300 total. I'm very happy with the performance of this setup.

One thing to keep in mind about the CRS305 is that it can't handle more than one or maybe two SFP+ copper modules. They use a lot of power and put out a lot of heat. I think the CRS309 has fewer restrictions.

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I find having a 120mm pc fan sitting on top blowing down through the case's top holes keeps everything sane. A 120mm fan matches the size almost perfectly, and there are even some usb powered ones available online. Running the fan slow and with rubber standoffs to help air move freely allows it to be nearly silent. Without that, even a single sfp+ to rj45 copper module can overheat and become unstable under load. Other than that the switches work great, perfect option for small scale cheapish 10G networking.

The transceivers get up to 90-95°C (enough to leave a little burn!) if you plug them next to each other.

They can work in that configuration (with up to 4 in that enclosure) but I'd only do it if you have a fan on the thing. It relies entirely on passive ventilation, and the enclosure gets hot, too, like 60°C or more!

Oh hey I just read the post about transceivers being slow only in one direction. I have the same problem on a different scale. Two X520T cards, one in a Dell T20 and the other in a Dell T30. Both connected with DACs to the CRS305. 9.something Gbps one direction, 7.something Gbps the other.

I haven't bothered to do much actual diagnosis on this because I'm satisfied with the speed as-is, but it's another illustration of weirdness where you'd least expect it.

Yeah; I've noticed asymmetric speeds in certain situations with the CRS305 as well... I thought it was just me, but I'm glad (sad?) to know someone else sees the same thing too :)

Could you recommend a PCIe adapter to receive a Nokia 3fe4960ac SFP+ transceiver (AT&T fiber) and maybe one or two 2.5G or 10G modules?

Oh I have no idea. You'd need to do some digging. I picked the Intel card because it was decently priced and I knew it would be reasonably compatible with what I was doing. Sounds like maybe you want a quad SFP+ card?

You can’t bypass AT&T’s absolutely craptastic fiber modem, even if you got the bidi transceiver you needed. The connection is encrypted with keys hardcoded into the modem.

And this thing doesn't have a JTAG?

For their craptastic router you could downgrade the firmware, use an old exploit to root, extract the keys, and then use those keys on your own Linux box to authenticate as the router…

For the fiber ONT (what I realize now you may be calling their fiber modem) I would love to see a similar attempt to get their hardware out of the loop.

Yeah, I’m referring to the ONT - which is now additionally bundled into their router + wifi box. There’s similar exploit to bypass the router part of the equation but you still need the ONT to negotiate the connection.

Do you have a link to this exploit?

Is it actually encrypted? or is it just 802.1x like it used to be (I moved away from the service area when they were still doing separate ONT and crappy 'internet gateway' that turned ethernet into ethernet.

The latter. The session negotiation is encrypted. You can technically shelve the unit after that’s been negotiated but it would need to be plugged back in each time your connection reset for some reason.

You can also keep the unit online, but only pass it the 802.1x frames. You'll be out pennies of electricity, of course.

Yeah, I saw some setups doing that. It seems like too much hackery involving a very core piece of network hardware, which is something I’d prefer to avoid. Fortunately it wasn’t my connection so I could live easier with deciding to keep the ONT.

I dunno, if the new ONTs are as braindead as the old Residential Gateways, it's probably worthwhile, but sure, it's a little hacky. I also wonder if you can get a higher data rate using the transceiver directly; GPON is 2.5G down/1.25G up IIRC, where the ONT I used was limited to 1G ethernet (although maybe you could do bonding, but obviously AT&T wouldn't set that up)

I get a symmetrical 1G on the GPON while I thought I had the best plan... maybe I need to pay even more?

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