tag:blogger.com,1999:blog-3993498847203183398.post5747657006048424605..comments2024-03-28T09:19:27.451+00:00Comments on RevK<sup>®</sup>'s ramblings: Number right?RevKhttp://www.blogger.com/profile/12369263214193333422noreply@blogger.comBlogger8125tag:blogger.com,1999:blog-3993498847203183398.post-82619347633279270972018-02-04T13:14:52.844+00:002018-02-04T13:14:52.844+00:00If you ever need to sell on Amazon, their essentia...If you ever need to sell on Amazon, their essential unique identifier for a product is the EAN/UPC barcode. They then group together "offers" from different sellers using that code. We hit problems where we listed items, and they were associated with completely different products, because somebody else had previously listed something that itself had no code against a then-unlisted barcode that actually belonged to the product we were trying to sell! Or they offer a multiple of an item (because it's small or low-value) using the code from the individual item. <br /><br />Because the sellercentral console lists items using the data *you* provided, not the generic, aggregated, data, you usually only find this out when somebody orders something, you ship it, and they then complain it's not what they expected. Much fun then ensues. ..not!<br /><br />The "solution" is to email amazon with photos of the real product, including barcode, and then, maybe, they will split the listing. But you still have an angry customer to deal with, who was expecting a product that you don't even have!Robhttps://www.blogger.com/profile/15492761714688454925noreply@blogger.comtag:blogger.com,1999:blog-3993498847203183398.post-70691951931894236332018-02-03T08:23:28.359+00:002018-02-03T08:23:28.359+00:00Some years ago I bought some dirt cheap usb ethern...Some years ago I bought some dirt cheap usb ethernet adapters on ebay. As well as being usb1.1 (sticker says 2.0) they all have identical MAC addresses!<br /><br />It appears there is no eeprom at all and this is 'by design'<br /><br />I only wanted them for some testing and I can change the MAC address at runtime so I kept them but caused quite a lot of head scratching when I first started trying to test some complex iptables rules - not least because which adapter was on which link wasn't stable and depended which usb port it was plugged in to.<br /><br />And twice now they've helped friends who have had network ports fail - leave them with one of them that gets things working again however slowly (and instructions to go and buy a proper one and then bin the toy)Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-3993498847203183398.post-15031933612865754552018-02-03T01:42:59.920+00:002018-02-03T01:42:59.920+00:00We actually did that on the first FireBricks...We actually did that on the first FireBricks...RevKhttps://www.blogger.com/profile/12369263214193333422noreply@blogger.comtag:blogger.com,1999:blog-3993498847203183398.post-76164945636789660242018-02-03T00:51:03.755+00:002018-02-03T00:51:03.755+00:00Here's an interesting example, with IP address...Here's an interesting example, with IP addresses: EMC have a range of NAS boxes that use IP for their back-end traffic, on two dedicated networks that are only meant for inter-box traffic (end-user traffic use different ports).<br /><br />The back-end network interfaces use IPs in the 128.221.252.0/24, 128.221.253.0/24, and 128.221.254.0/24 ranges. Yes, those are public IP addresses. But, EMC have the entire 128.221.0.0/16 range. And, looking at routeviews, it seems that those three /24s are not being announced on the Internet.<br /><br />So, rather than pick some random 10.xxx range (that might conflict with customers), EMC allocated a chunk of their public range, and then ensured that it would not conflict with anything.Anonymoushttps://www.blogger.com/profile/04428564417365417467noreply@blogger.comtag:blogger.com,1999:blog-3993498847203183398.post-39925261840616206752018-02-02T17:25:47.008+00:002018-02-02T17:25:47.008+00:00With MAC addresses you do have the distinction of ...With MAC addresses you do have the distinction of whether they are universally or locally administered, indicated by the second LSB of the first octet - the latter not needing to be allocated by anybody and thus you are free to make them up.<br /><br />I don't know if there's anything which states e.g. that you should use universally administered addresses on items you sell or intend to be used outside of a network you control...Alexhttps://www.blogger.com/profile/13535977952530779134noreply@blogger.comtag:blogger.com,1999:blog-3993498847203183398.post-14838788785174522382018-02-02T10:28:07.176+00:002018-02-02T10:28:07.176+00:00We bought 2 very dodgy webcams a couple of years b...We bought 2 very dodgy webcams a couple of years back, and their vendors weren't even trying with the MAC addresses: 00:00:00:00:0F:46 and 00:00:00:00:0F:48 !Matthewhttps://www.blogger.com/profile/04311149395810537121noreply@blogger.comtag:blogger.com,1999:blog-3993498847203183398.post-7143455847761097982018-02-02T10:07:31.935+00:002018-02-02T10:07:31.935+00:00Wow, and indeed the way MACs are transmitted on th...Wow, and indeed the way MACs are transmitted on the wire is rather counter intuitive.RevKhttps://www.blogger.com/profile/12369263214193333422noreply@blogger.comtag:blogger.com,1999:blog-3993498847203183398.post-11738169656297186752018-02-02T10:05:01.273+00:002018-02-02T10:05:01.273+00:00I don't know if it's still the case, but h...I don't know if it's still the case, but historically there was never any standard for endianness in MAC address encoding. In the mid-1990s I worked at IBM and discovered they encoded theirs backwards compared to everyone else, resulting in the potental for collisions.DougMhttps://www.blogger.com/profile/05242392819960202688noreply@blogger.com