Author: john

Categories
Admin Proxy

Google Hangouts Meet – what do these IPs all have in common?

2021 update

142.250.82.77

142.250.82.113

142.250.82.28

142.250.82.126

2020 update

142.250.82.42

142.250.82.71
142.250.82.78
209.85.144.127
74.125.250.71

Suspected additional IPs

And I observed the user agent “Google Hangouts” trying these IPs, but by the FQDN mtalk.google.com (whose resolution must by very dynamic) rather than raw IP:

142.250.31.188
172.253.122.188
172.253.63.188

Older IPs
173.194.207.127
209.85.232.127
64.233.177.127
64.233.177.103
74.125.196.127

They all have been used by Google’s Hangouts Meet based on my observation.
If you have an environment which uses proxy authentication, the above IPs do not play well with that. So you’ll need to disable proxy authentication for them for Hangouts Meet to work.

Otherwise you can do the initial connect but will be dropped after about 45 seconds.

Finally, although you can look up each individually and learn of its association to Google, Google’s own documentation is devoid of any references to them. That is unfortunate.

So the IPs in actual use is probably much larger, but these are what I’ve observed over the course of a few days of testing.

What I’ve done
Google is very hard to reach. They only provide indirect means for regular users. So not knowing any insiders I submitted feedback at https://meet.google.com/ which is what they suggest. I provided a detailed description. I doubt they will do anything with my feedback. We’ll see. Update. Correct. Months have passed and they never bothered to get back to me.

Conclusion
Google has an undocumented dependency on a whole set of IPs for hangout Meets to actually work through a proxy which requires authentication. Contacting Google for more information is probably impossible, but I will try.

Categories
Consumer Tech

Consumer Tech: amazing little Bluetooth adapter for your car

Intro
My old car I decided finally needed a touch of Bluetooth connectivity. But how to do it without spending a fortune?

The details
I found this amazingly inexpensive gadget on Amazon that describes itself as follows: Handsfree Call Car Charger,Wireless Bluetooth FM Transmitter Radio Receiver&Mp3 Music Stereo Adapter,Dual USB Port Charger Compatible for All Smartphones,Samsung Galaxy,LG,HTC,etc.

I guess it’s normally $16 but I bought on Cyber Monday so it was about $12. 12 dollars! I think if I had gone to the dealer for an after-market solution it would have been $500.

The bad first
Let’s get the bad out of the way, bearing in mind my expectations were rather low so I may be leaving out some obvious “of course it doesn’t have that…” type of stuff.

This device does an FM broadcast and you pick an unoccupied FM frequency to listen to it. On the other side it connects to a Bluetooth device such as a phone. In IT terms I’d call it a gateway since it converts one protocl to another (Bluetooth to FM). Having read the reviews, but not finding anything addressing my interests, my idea was to continue to use my FM stations, and put the station used by this device on a preset so when a call comes in to my phone I hit the station preset and accept the call on the device.
Well, you basically can’t listen to other FM stations as long as this thing is powered up. So even tuned to 88.7 at the far end of the dial, it interferes with stations up and down the dial for some reason. It’ not impossible but you’d have to have a high tolerance for static to use it that way.

Also, I’ve read that these little things break on some people after a few months. But I would no feel cheated, remember, low expectations?

The good
– microphone is good
– compatible with Samsung
– capable of audio program controls
– boots up quickly, maybe 10 seconds

My solution
I only really listen to NPR. I tried the WNYC app in the Playstore. I used to think it was buggy – stopping at random times. But I’ve had good luck my first few trips. Plays great through this thing! In many ways it’s better than FM because I don’t have to change NPR stations as I drive to work, etc, and its signal is often better. There is some static background however. Now my phone GPS talks to me through the speakers (it used to be silent in the car).

The unknown
Not sure about outbound calls to much. If you hit the button twice it seems to call the last dialed number. There are these settings U01, U02, U30. maybe those are for speed dialing?
Precisely why it has to so broadly interfere with all FM stations is a mystery.

Being a thoughtful person, I also wonder what it does to the FM reception of cars around me, ha ha? Could they pick up my call? Now that I think of it, I do remember hearing someone’s phone call on my FM radio once, many years ago. Use of an aux cord would be a way around that, but this little device does not support that.

The amazing
How cuold they pack all this tech, make something that basically works as it’s supposed to, and sell it for $12? I’m in awe.

References and related
https://smile.amazon.com/gp/product/B01M0SFMIH/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1

Categories
Admin Security

Great serial port concentrator: Raritan Dominion

Intro
Every now and then you find a product that is a leap ahead of where you were. Such is the case for us with regards to our product of choice for serial consoles.

The old
For Bluecoat (Symantec) proxy and AV systems, we had been using an ancient Avocent CPS device. It permitted ssh connection. It was slow and the menu very limited. But it did permit us to connect multiple serial consoles to one concentrator device at least.
For low-end firewalls we had been using DigiConnects, one per firewall. They are small, which may be thir one advantage. They are tricky to initially set up. Then they are slow to use.

In with the new
We heard about the Raritan Dominion line of products, stranegly enough, from some IT guys in Europe. It’s strange because they are right here in New Jersey – the company name probably comes form the Raritan river. But our usual reseller never heard of them. The specific device is a Dominion SXII.

It’s so much better than those older products. You can use their GUI to connect. This is a vendor who got their act together and eliminated Java. So many other security vendors have yet to do that, incredible as it is to say that.
It tries to autosense the wiring of the serial connector. That doesn’t always work, but it’s very easy for you to hardwire a port as DCE, or if that dosn’t work, try DTE. I use one type for my Symantec devices, another for firewalls.

Labelling the port with meaningful names is a snap, of course.

The Digis would interfere with the reboot process of the firewall so we’d have to detach them if we were going to rbeoot the firewall. These do not. So much better…

You can combine them with power control but we aren’t going to do that.

Don’t want to use the GUI? No problem, console access through ssh is also possible. Of configure dedicated ports that you ssh to for individual consoles.

Sending signals and cleanly disconnecting is easy with their menuss. Connecting to multiple consoles is alsono problem.

They have something called in-the-rack access. I know this will be useful but I haven’t figured out how to use it yet. But if it is what it sounds like it is, it will allow me to be in the server room and access any console by using a direct connection of some sort to the Dominion SXII.

And they’re just plain faster. A lot faster.

And, considering, they’re not so expensive.

They worked so much better than expected that we pretty much immediately filled up the ports with firewalls and other stuff.

Conclusion
A leap forward in productivity was realized by utilizing Raritn’s Dominion SXII serial port concentrator. Commissioning new security gear has never been esaier…

References and related
Raritan’s web site: https://www.raritan.com

Categories
Admin Perl

Counting active leases on an old ISC DHCP server

Intro
Checkpoint Gaia offers a DHCP service, but it ias based on a crude and old dhcp daemon implementation frmo ISC. Doesn’t give you much. Mostly just the file /var/lib/dhcpd/dhcpd.leases, which it constantly updates. A typical dhcp client entry looks like this:

 
lease 10.24.69.22 {
  starts 5 2018/11/16 22:32:59;
  ends 6 2018/11/17 06:32:59;
  binding state active;
  next binding state free;
  hardware ethernet 30:d9:d9:20:ca:4f;
  uid "\0010\331\331 \312O";
  client-hostname "KeNoiPhone";
}


The details
So I modified a perl script to take all those lines and make sense of them.
I called it lease-examine.pl.
Here it is

#!/usr/bin/perl
# from https://askubuntu.com/questions/219609/how-do-i-show-active-dhcp-leases - DrJ 11/15/18
 
my $VERSION=0.03;
 
##my $leases_file = "/var/lib/dhcpd/dhcpd.leases";
my $leases_file = "/tmp/dhcpd.leases";
 
##use strict;
use Date::Parse;
 
my $now = time;
##print $now;
##exit;
# 12:22 PM 11/15/18 EST
#my $now = "1542302555";
my %seen;       # leases file has dupes (because logging failover stuff?). This hash will get rid of them.
 
open(L, $leases_file) or die "Cant open $leases_file : $!\n";
undef $/;
my @records = split /^lease\s+([\d\.]+)\s*\{/m, <L>;
shift @records; # remove stuff before first "lease" block
 
## process 2 array elements at a time: ip and data
foreach my $i (0 .. $#records) {
    next if $i % 2;
    ($ip, $_) = @records[$i, $i+1];
    ($ip, $_) = @records[$i, $i+1];
 
    s/^\n+//;     # && warn "leading spaces removed\n";
    s/[\s\}]+$//; # && warn "trailing junk removed\n";
 
    my ($s) = /^\s* starts \s+ \d+ \s+ (.*?);/xm;
    my ($e) = /^\s* ends   \s+ \d+ \s+ (.*?);/xm;
 
    ##my $start = str2time($s);
    ##my $end   = str2time($e);
    my $start = str2time($s,UTC);
    my $end   = str2time($e,UTC);
 
    my %h; # to hold values we want
 
    foreach my $rx ('binding', 'hardware', 'client-hostname') {
        my ($val) = /^\s*$rx.*?(\S+);/sm;
        $h{$rx} = $val;
    }
 
    my $formatted_output;
 
    if ($end && $end < $now) {
        $formatted_output =
            sprintf "%-15s : %-26s "              . "%19s "         . "%9s "     . "%24s    "              . "%24s\n",
                    $ip,     $h{'client-hostname'}, ""              , $h{binding}, "expired"               , scalar(localti
me $end);
    }
    else {
        $formatted_output =
            sprintf "%-15s : %-26s "              . "%19s "         . "%9s "     . "%24s -- "              . "%24s\n",
                    $ip,     $h{'client-hostname'}, "($h{hardware})", $h{binding}, scalar(localtime $start), scalar(localti
me $end);
    }
 
    next if $seen{$formatted_output};
    $seen{$formatted_output}++;
    print $formatted_output;
}

Even that script produces a thicket of confusing information. So then I further process it. I call this script dhcp-check.sh:

#!/bin/sh
# DrJ 11/15/18
# bring over current dhcp lease file from firewall FW-1
date
echo fetching lease file dhcpd.leases
scp admin@FW-1:/var/lib/dhcpd/dhcpd.leases /tmp
# analyze it. this should show us active leases
echo analyze dhcpd.leases
DIR=`dirname $0`
$DIR/lease-examine.pl|grep active|grep -v expired > /tmp/intermed-results
# intermed-results looks like:
#10.24.76.124   : "android-7fe22a415ce21c55" (50:92:b9:b8:92:a0)    active Thu Nov 15 11:32:13 2018 -- Thu Nov 15 15:32:13 2018
#10.24.76.197   : "android-283a4cb47edf3b8c" (98:39:8e:a6:4f:15)    active Thu Nov 15 11:37:23 2018 -- Thu Nov 15 15:32:14 2018
#10.24.70.236   : "other-Phone"            (38:25:6b:79:31:60)    active Thu Nov 15 11:32:24 2018 -- Thu Nov 15 15:32:24 2018
#10.24.74.133   : "iPhone-de-Lucia"          (34:08:bc:51:0b:ae)    active Thu Nov 15 07:32:26 2018 -- Thu Nov 15 15:32:26 2018
#exit
# further processing. remove the many duplicate lines
echo count active leases
awk '{print $1}' /tmp/intermed-results|sort -u|wc -l > /tmp/dhcp-active-count
echo count is `cat /tmp/dhcp-active-count`

And that script gives my what I believe is an accurate count of the active leases. I run it every 10 minutes from SiteScope and voila, we have a way to make sure we’re coming close to running out of IP addresses.

Categories
Web Site Technologies

The IT Detective Agency: Cisco Jabber Carriage Return problem fixed

Intro
Cisco Jabber is a pretty good IM application. I’ve seen how it is a true productivity enhancer. But not so much when it doesn’t work right.

The symptoms
I hadn’t rebooted for awhile. I had a bunch of open conversations. Then all of a sudden, I could no longer send additional Jabbers (IMs, messages, or whatever you call them). I would type my message, hit ENTER (<CR>), and that action would just give send the cursor to the beginnning of a new line below the one I typed in my message box, like a typewriter. I soon realized that I had no way to SEND what I was typing because you use ENTER to do that!

A quick Internet search revaled nothing (hence this article). So I restarted Jabber and that got things working again, but of course I lost all my conversations.

As this happened again, I looked more closely. I eventually noticed this security pop-up was associated with this ENTER problem:

Being a security-minded person I kept clicking No to this pop-up.

Then I noticed the correlation. As soon a I clicked No on that pop-up, my ‘s began to work as expecetd. After a few minutes they stop working again, I hunt for the pop-up, and click No again. And it goes on like this all day.

Hint on finding the pop-up
Jabber has a main narrow window which cpontains all the contacts and other links, and the conversation window. Highlight the main narrow wnidow and the pop-up will appear (if therer is one). Otherwise it can be hard to find.

Why is there a security alert?
Being a srot of certificate expert, I felt obliged to delve into the certificate itself to help whoever may try to solve this. I captured the certificate and found that it is a self-signed certificate! No wonder it’s not accepted. So our Unified Communications vendor, in their infinite wisdom, used self-signed certificates for some of this infrastructure. Bad idea.

I suppose I could accept it, but I’d prefer they fix this. I don’t want end users becoming comfortable overriding security pop-ups.

Conclusion
The sudden inability to use ENTER within Cisco Jabber is explained and a corrective action is outlined.

Case closed!

Categories
Scams Spam

Latest spear phishing: your password plus extortion

Intro
Three users that I know at a certain company have all received spear phishing emails worded very much like this one:

Spear Phishing shows you your password and extorts you

The details
I don’t really have many more details. One user described it to me as follows. He got this email at work. It displayed to him a password which he uses for some of his personal accounts and maybe for a few work-related logins. He said the wording was very similar to the one I showed in the above screenshot.

This one comes from IP 40.92.6.45, which is a legitimate Microsoft-owned IP. So it has an air of legitimacy to traditoinal spam filters.

I htikn all the users are reluctant to pursue the normal methods o reporting phishing, which involve sending the entire email to some unknown group of analysts because the email does in fatc contain a legitimate password of theirs. This makes it that much harder for an incident repsonse team to kick into gear and start a detailed analysis.

I mentioned three users – those are just the ones brought to my attention, and I’m not even in the business any more. So by extrapolation, this has probably occurred to many more users at just this one company. It’s disturbing…

November update
Another one came in to a different user. I have the text of this one and have only changed the recipient information.

From: [email protected] <[email protected]>
Sent: Thursday, November 29, 2018 11:55 AM
To: Dr J <[email protected]>
Subject: [email protected] has been hacked! Change your password immediately!
 
Hello!
 
I have very bad news for you.                                                                                                                                 03/08/2018 - on this day I hacked your OS and got full access to your account [email protected] On this day your account [email protected] has password: drj1234
 
So, you can change the password, yes.. But my malware intercepts it every time.
 
How I made it:
In the software of the router, through which you went online, was a vulnerability.
I just hacked this router and placed my malicious code on it.
When you went online, my trojan was installed on the OS of your device.
 
After that, I made a full dump of your disk (I have all your address book, history of viewing sites, all files, phone numbers and addresses of all your contacts).
 
A month ago, I wanted to lock your device and ask for a not big amount of btc to unlock.
But I looked at the sites that you regularly visit, and I was shocked by what I saw!!!
I'm talk you about sites for adults.
 
I want to say - you are a BIG pervert. Your fantasy is shifted far away from the normal course!
 
And I got an idea....
I made a screenshot of the adult sites where you have fun (do you understand what it is about, huh?).
After that, I made a screenshot of your joys (using the camera of your device) and glued them together.
Turned out amazing! You are so spectacular!
 
I'm know that you would not like to show these screenshots to your friends, relatives or colleagues.
I think $709 is a very, very small amount for my silence.
Besides, I have been spying on you for so long, having spent a lot of time!
 
Pay ONLY in Bitcoins!
My BTC wallet: 1FgfdebSqbXRciP2DXKJyqPSffX3Sx57RF
 
You do not know how to use bitcoins?
Enter a query in any search engine: "how to replenish btc wallet".
It's extremely easy
 
For this payment I give you two days (48 hours).
As soon as this letter is opened, the timer will work.
 
After payment, my virus and dirty screenshots with your enjoys will be self-destruct automatically.
If I do not receive from you the specified amount, then your device will be locked, and all your contacts will receive a screenshots with your "enjoys".
 
I hope you understand your situation.
- Do not try to find and destroy my virus! (All your data, files and screenshots is already uploaded to a remote server)
- Do not try to contact me (you yourself will see that this is impossible, the sender address is automatically generated)
- Various security services will not help you; formatting a disk or destroying a device will not help, since your data is already on a remote server.
 
P.S. You are not my single victim. so, I guarantee you that I will not disturb you again after payment!
 This is the word of honor hacker
 
I also ask you to regularly update your antiviruses in the future. This way you will no longer fall into a similar situation.
 
Do not hold evil! I just do my job.
Good luck.

Conclusion
A new disturbing type of spear phishing campaign is presented. The email presents an actual password (no hint as to how the hacker obtained it) and then tries to extort the user for quite a bit of money to avoid reputation-damaging disclosures to their close associates.

References and related
This is a useful site, albeit a little frightening, that shows you the many sites that have leaked your Email address due to a data breach: https://haveibeenpwned.com/

Categories
Network Technologies

Voice and data vlans on one switch port, no vlan tagging: how does that work?

Intro
We had a Cisco video conference unit pick up an IP from a data vlan whereas we expected it to pick it up from a voice vlan, where we had assigned it a static IP. What happened?

The details
I have to admit I never paid attention to the switch ports in the offices. All these years and I didn’t really appreciate the fact that you can plug in either a PC or a Cisco phone to the same switch port, yet the PC “knows” to go onto a data vlan while the phone “knows” to put itself onto a voice vlan. How cuold that be?

Naively, just talking it out, I had this jumble of “facts” in my mind:

– sharing vlans on one switch port is done through vlan tagging
– the equipment plugged in must know the switch port is using vlan tagging or else disastrous results occur (see this post for some examples)
– if in addition you’re a PC using DHCP, how would you know which valn to go onto? How would you learn the connection is tagged?
– well, there can be a native vlan in addition to tagged vlans. Maybe they used that?

Fortunately I have some friends with access to the switch config. Here it is for one specific typical port:

interface FastEthernet0/2
description Data & Voice vlanC
switchport access vlan 103
switchport mode access
switchport voice vlan 703
...

I puzzled over that for awhile because, well, what does it mean?? In my world of servers you have two port types: access ports and truink ports. Trunk ports are the ones that have tagged vlans. Access ports provide a single unttagged vlan’s traffic to the port.

It’s pretty clearly declaring this switch port to be an access port, not a trunk port. And yet two vlans are referred to. There’s this command I’ve never seen or used before swithcport voice. How does this fit with the jumble of facts above? The jumble of facts need to be amended…

I asked another expert and he said he heard that the Cisco phones use something called LLDP – link layer discovery porotocol. From researching the predecessor protocol was CDP – Cisco Discovery protcol.

Switchport voice vlan 703 is something like introducing tagging for vlan703, if I read the Cisco documentation correctly.

The magic happens
This is often described as magic or voodoo so we will treat it like that too! A Cisco phone uses LLDP to learn from the switch that the voice vlan is 703. Then somehow it tags(?) its traffic to use only that vlan, even for its DHCP discover. A PC or any other normal host by contrast does not use LLDP and is only exposed to the data vlan 103 (the “native” vlan) so it gets an IP from doing DHCP discover on that vlan.

Do I believe my own explanation? Not really. It’s the best I got. I really should do a packet trace to confirm but who has the time?

That video conference unit? They say when they boot it a second time it jumps onto the correct vlan and picks up the desired static IP. Again, no one’s really sure why.

Conclusion
Strange DHCP behavious on the part of a Cisco video conference unit forces us to think through how data + voice on one switch port might actually be working on a typical Cisco-powered office environment. We probably – definitely – didn’t nail it, but we must be close to the essentially correct answer.

References and related
As always Wikipedia has an article somewhat explaining LLDP

Categories
Linux Raspberry Pi

Solution to this week’s NPR puzzle using simple Linux commands, again

Intro
As I understood it, this week’s NPR puzzle is as follows. Think of a figure from the Bible with five letters. Move each letter three back, e.g., an “e” becomes a “b.” Find the Biblical figure which becomes an ailment after doing this transformation.

Initial thoughts
I figured this would be eminently amenable to some simple linux commands like I’ve done with previous puzzles (most are not, by the way). I was having a hard time doing these transformations in my head while I was driving, and the first names I tried came up empty, such as Jesus or Moses.

So I figured I could write a program to do the character transformations on each and every word and I could probably find a downloadable text version of the Bible. I didn’t find a pure text version, but I did download an HTML version, which is close enough for our purposes.

Then I was going to just keep the five-letter words and do this transformation on all of them and match against dictionary words. Then I would have taken just those matches and scanned by hand to look for words that are ailments, hoping there wouldn’t be too many matched words to contend with.

Finally settled on a different approach
That looked like a bit of work so I thought about it and decided there had to be a resource for just the figures in the Bible, and voila, there is, in Wikipedia, see the references.

rot13
Rot13 is a famous cipher (encryption is too strong a word to describe this simple approach), where A becomes N, B becomes O, etc. I had a feeling the tr command in linux might be able to do this but didn’t know how. So I searched for linux, tr and rot13 and found an example online. It was easy to adapt.

We need what you could call a rot -3. Here is the command.

$ tr 'A‐Za‐z' 'X‐ZA‐Wx‐za‐w'

So I put the text of the Wikipedia page of Biblical figures into a text file on my linux server, into a file called list-of-biblical-figures. It looks like this:

Adam to David according to the Bible
Creation to Flood
 
    Adam Seth Enos Kenan Mahalalel Jared Enoch Methuselah Lamech Noah Shem
 
Cain line
 
    Adam Cain Enoch Irad Mehujael Methusael Lamech Tubal-cain
 
Patriarchs after Flood
 
    Arpachshad Cainan Shelah Eber Peleg Reu Serug Nahor Terah Abraham Isaac Jacob
 
Tribe of Judah to Kingdom
 
    Judah Perez Hezron Ram Amminadab Nahshon Salmon Boaz Obed Jesse David
...

I was going to tackle just pulling the figures with five-character names, but the whole list isn’t that long so I skipped even that step and just put the list through as is:

$ cat list-of-biblical-figures|tr 'A‐Za‐z' 'X‐ZA‐Wx‐za‐w'

comes back as

Xaxj ql Axsfa xzzloafkd ql qeb Yfyib
Zobxqflk ql Cilla
 
    Xaxj Pbqe Bklp Hbkxk Jxexixibi Gxoba Bklze Jbqerpbixe Ixjbze Klxe Pebj
 
Zxfk ifkb
 
    Xaxj Zxfk Bklze Foxa Jbergxbi Jbqerpxbi Ixjbze Qryxi-zxfk
 
Mxqofxozep xcqbo Cilla
 
    Xomxzepexa Zxfkxk Pebixe Bybo Mbibd Obr Pbord Kxelo Qboxe Xyoxexj Fpxxz Gxzly
 
Qofyb lc Graxe ql Hfkdalj
 
    Graxe Mbobw Ebwolk Oxj Xjjfkxaxy Kxepelk Pxijlk Ylxw Lyba Gbppb Axsfa
...
    Ebola
...

So it’s all gibberish as you might hope. Then towards the end you come across this one thing and it just pops out at you. As is my custom I won’t give it away before the deadline. [update] OK. Submission deadline has passed. Ebola just really popped out. Going back to the original text, you see it lines up with Herod. So there you have it.

I double-checked and confirmed this also works on a Raspberry Pi. I’ve come to realize that most people don’t have their own server, but hundreds of thousands or perhaps millions have a Raspberry Pi, which is a linux server, which makes techiques like this accessible. And fun.

Conclusion
I show a technique for using a linux server such as a Raspberry Pi to solve this week’s NPR puzzle. A very simple approach worked. In fact I was able to solve the puzzle and write this post in about an hour!

References and related
HTML version of Bible: https://ebible.org/Scriptures/eng-web_html.zip
Biblical figures: https://en.wikipedia.org/wiki/List_of_major_biblical_figures
An earlier NPR puzzle solved with linux command line techniques

Categories
DNS

The IT detective agency: rogue IPv6 device messes up DHCP for entire subnet

Intro
This was a fascinating case insofar as it was my first encounter with a real life IPv6 application. So it was trial by fire.

The details
I think the title of the post makes clear what happened. The site people were saying they can ping hosts by IP but not by DNS name. So basically nothing was working. I asked them to do an ipconfig /all and send me the output. At the top of the list of DNS servers was this funny entry:

IPv6 DNS server shows up first

I asked them to run nslookup, and sure enough, it timed out trying to talk to that same IPv6 server. Yet they could PING it.

The DNS servers listed below the IPv6 one were the expected IPv4 our enterprise system hands out.

My quick conclusion: there is a rogue host on their subnet acting as an IPv6 DHCP server! It took some convincing on my part before they got on board with that idea.

But I goofed too. In my haste to move on, I confused an IPv6 address with a MAC address. Rookie IPv6 mistake I suppose. It looked strange, had letters and even colons, so it kind of looks like a MAC address, right? So I gave some quick advice to get rid of the problem: identify this address on the switch, find its port and disable it. So the guy looked for this funny MAC address and of course didn’t find it or anything that looked like it.

My general idea was right – there was a rogue IPv6 DHCP server.

My hypothesis as to what happened
The PCs have both an IPv4 as well as an IPv6 stack, as does just about everyone’s PC. These stacks run independently of each other. Everyone blissfully ignores the IPv6 communication, but that doesn’t mean it’s not occurring. I think these PCs got an IPv4 IP and DNS servers assigned to them in the usual way. All good. Then along came a DHCPv6 server and the PC’s IPv6 stack sent out a DHCPv6 request to the entire subnet (which it probably is doing periodically all along, there just was never a DHCPv6 server answering before this). This time the DHCPv6 server answered and gave out some IPv6-relevant information, including a IPv6 DNS server.

I further hypothesize that what I said above about the IPv4 and IPv6 stacks being independent is not entirely true. These stacks are joined in one place: the resolving nameservers. You only get one set of resolving namesevrers for your combined IPv4/IPv6 stacks, which sort of makes sense because DNS servers can answer queries about IPv6 objects if they are so configured. So, anyway, the DHCPv6 client decides to put the DNS server it has learned about from its DHCPv6 server at the front of the existing nameserver list. This nameserver is totally busted, however and sits on the request and the client’s error handling isn’t good enough to detect the problem and move on to the next nameserver in the list – an IPv4 nameserver which would have worked just great – despite the fact that it is designed to do just that. And all resolution breaks and breaks badly.

What was the offending device? They’re not saying, except we heard it was a router, hence, a host introduced by the LAN vendor who can’t or won’t admit to having made such an error, instead making a quiet correction. Quiet because of course they initially refused the incident and had us look elsewhere for the source of the “DHCP problem.”

Alternate theory
I see that IPv6 devices do not need to get DNS servers via DHCPv6. They can use a new protocol, NDP, neighbor discovery protocol. Maybe the IPv6 stack is periodically trying NDP and finally got a response from the rogue device and put that first on the list of nameservers. No DHCPv6 really used in that scenario, just NDP.

Useful tips for layer 2 stuff
Here’s how you can find the MAC of an IPv6 device which you have just PINGed:

netsh interface ipv6 show neighbors

from a CMD prompt on a Windows machine.

In Linux it’s

ip ‐6 neigh show

Conclusion
Another tough case resolved! We learn some valuable things about IPv6 in the process.

References and related
I found the relevant commands in this article: https://www.midnightfreddie.com/how-to-arp-a-in-ipv6.html

Categories
Web Site Technologies

Where is my IP without the aggressive ads

Intro
To locate where any IP address is located – known as geoip – you can do a simple duckduckgo search and get an idea, but you may also get sucked into one of those sites that provides a service while subjecting you to a lot of advertising. So I prefer to have the option to go to the source.

For that I kind of like this site: https://www.maxmind.com/en/geoip-demo

Maxmind also has a free downloadable database of all IPs known as GeoLite2. If I get time I may explore using it.

References and related
https://www.maxmind.com/en/geoip-demo