I swapped out my T-Mobile SIM card yesterday for one of their new Advanced Security SIMs, and WiFi calling suddenly stopped working. I poked around the Internet and found a lot of posts about REG09 and REG99, but not much on REG90 except one misinformed post where someone said that they had to return their phone.
If you're like us (and most places), you want to look at traffic from time to to time...or all the time. Juniper doesn't let you create a "span" port or mirror port on their routers -- only on their switches. You can't get any of the layer 2 stuff, only layer 3 and up (family inet).
One of my goals in writing this blog is to help other people in the operations field. It's not a point of bragging or telling other people how to do their job. It's just a helpful guide that isn't full of sales pitches. That said, I'm going to say something somewhat inflammatory. You're crazy if you still run 1U "pizzabox" servers as your web front ends. Seriously.
As operations employees, we should strive to reduce downtime (at a reasonable cost) whenever we can. Sometimes, it's the little things that can go a long way. Using PDU secure sleeves in your datacenter racks is a simple, low-cost method to prevent admin-induced outages when working on equipment.
PDU outlet tolerances and cabling tolerances don't always match up. If you've ever used a PDU that uses C14 or C20 connectors, you know what I mean. You plug something in, but the cable on the PDU side is a bit jiggly. It's in there but not snug. Not like what you expect from something plugged into a 110V 3-prong outlet. Luckily, there's a cheap, simple solution called secure sleeves.
Secure sleeves are plastic molds that simply slide over your existing power cables. When inserted into the outlet, the sleeves compress, and friction holds the plug in place. Brilliant! I've posted a quick video (below) showing how well they work.
We buy ours from Stay Online for 50 cents each. They even have the inserts for the other C13/C19 sides. Stay Online says that they only work with PowerFig or Yung Li cables; not a problem for us as we buy all of our PowerFig cables from them. You should check out the stuff at Stay Online, they've got good stuff at good prices. No, I don't get any referral money from them; I'm just a happy customer.
This post is short and sweet since it probably affects a narrow range of people. If you run Aruba wireless gear and your Android users have started to complain about connectivity issues, here's the fix. Set "no broadcast-filter arp" on your wlan virtual-ap.
The longer story is that Aruba gear (by default) will send ARP responses as unicast instead of broadcast. This is a trick to conserve RF network capacity and extend battery life for devices. The problem is that Android (and I'm guessing Linux) devices treat the responses as invalid. It sent a broadcast and receieved a unicast response.....that does seem kind of fishy. I don't know if this behavior is against some sort of RFC or is frowned upon or what. I think it sounds neat....until it breaks stuff.
No other devices we saw (Macs, PCs, iPhones) were affected by this. The Android phones would associate with a radio, join the network, get an IP, then go nowhere. No kind of network access would work. The tell-tale test was a basic ping from the controller to the device. That failed even with static ARP entries on the controller (because the client was ignoring ARP responses).
You want to use a RHEL 6/CentOS 6 server as an IPSec/VPN gateway?
Here's the tl;dr.... don't do it. Buy some Juniper SRX210's on eBay for $200/each instead.
The Linux kernel team massively broke IPSec performance somewhere between kernels 2.6.18 and 2.6.35. The good news is that it's supposedly fixed in 2.6.35. I haven't tested it, but reports are that it works OK. So if you must stay with RHEL or CentOS, compile your own kernel (I'd recommend doing that anyway).
So back to the long story.
A Creole coonass just trying to get by. I live in San Francisco and work as a digital plumber for the joint that runs this thing. (Square/Weebly) Thoughts are mine, not my company's.