Spyke
Treczoksreply
lemmy.world

Try pinging 127.1 - it is the same, but shorter.

Just another tipp from someone who learned TCP/IP from reading the sources over three decades ago...

45
Treczoksreply
lemmy.world

This is a special case. This resolves to 0.0.0.0, and technically cannot be routed. Some(!) systems use it as a kind of alias for all local network addresses, but it is not a given.

6

I'm aware. Conveniently this works on all the systems I've tried, making it useful for testing local services (e.g. ssh 0).

2
dwtreply
feddit.org

That resolves to 0.0.0.0 - rarely useful

1

But it does not work by definition, it is non-routable. That some systems use it as an alias is a different issue.

1
Randelungreply
lemmy.world

Pretty insane that around 0.4% of all IPv4 addresses are wasted.

9
lemmy.world

Apple (and others) used to have an A class. I think they gave some of it back to the pool.

2
sh.itjust.works

A few years ago my old university finally went with NAT instead of handing out public IPs to all servers, workstations and random wifi clients. (Yes, you got a public IP on the wifi. Behind a firewall, but still public.) I think they have a /16 and a few extra /24s in total.

3
lemmy.zip

Honestly there isn't much reason to go with NAT unless you are looking to lease/sell IPs

The sad part is that almost no universities do IPv6

1

I kinda get why organisations don’t migrate.

IPv6 just hands you a bag of footguns. Yes, I want all my machines to have random unpredictable IPs. Having some extra additional link local garbage can’t hurt either, can it? Oh, and you can’t run exhaustive scans over your IP ranges to map out your infra.

I’m not saying people shouldn’t migrate, but large orgs like universities have challenges to solve, without any obvious upside to the cost. All of the above can be solved, but at a cost.

1
lemmy.world

ping 1.1 also works. It resolves to 1.0.0.1, which is Cloudflare's secondary DNS

68
yeehawreply
lemmy.ca

Oh shit. Didn't know this either. Kind of like ipv6 in a way

5
talreply
lemmy.today

IPv4 has some other features too.

$ ping 0x8.02004010
PING 0x8.02004010 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=116 time=22.8 ms

That'll be Google's root DNS server, using hexadecimal and octal representations.

19

it's so simple!


ping -c 4 $(mysql -u frodo -p keepyoursecrets -D /home/pingtargets.db -se "SELECT ip FROM servers ORDER BY RAND() LIMIT 1;")
30

I fondly remember regularly logging into simtel20.wsmr.army.mil back in the days (WSMR=White Sands Missile Range). No issue, just used "anonymous" as the username, and your email address as the password. And even the email address was just a convenience...

5
lemmy.dbzer0.com

Ah yeah there's a little misunderstanding. IP addresses can be represented as 32-bit unsigned integer numbers, where each 8-bit chunk is separated by a dot.

So the conversion is: 133742069 (decimal) -> 00000111111110001011110111110101 (binary) -> 00000111.11111000.10111101.11110101 (8-bit chunks) -> 7.248.189.245 (resulting IP)

26
Chrisreply
lemmy.world

I don't get it, the first octet (?) max is 256.

2

Yes, but you can write it in different ways. If the numeric string contains a dot, left of it must be between 0 and 255, and is put in the highest byte of the address. If the rest also contains a dot, repeat, but put it into the second highest byte.

BUT: if the string does not contain a dot, the number is put into the remaining bytes.

So 123.256 is a valid address. The 123 goes into the top byte, the 256 goes into the remaining three bytes, so the address would be 123.0.1.0.

Most common example is 127.1, which is short for 127.0.0.1 - the localhost address.

21
remotelovereply
lemmy.ca

255

Small correction, but an important one: 0 is a number too.

In terms of IP masking and broadcast addresses, the max is 255.255.255.255

5

Oof of course. 256 entries from 0 - 255.

It's been a long long time since my ccent

2

In nearly forty-ish years on the internet (yes, I was around before the web), I have not seen someone expressing an internet address in octal (before this discussion), although I remember that it is legal. Using hex, yes, but not octal.

2

Or, if you're me,

$ ping 16843009                
PING 16843009 (1.1.1.1) 56(84) bytes of data.           
64 bytes from 1.1.1.1: icmp_seq=1 ttl=53 time=4.06 ms   
64 bytes from 1.1.1.1: icmp_seq=2 ttl=53 time=4.04 ms   
64 bytes from 1.1.1.1: icmp_seq=3 ttl=53 time=4.05 ms   ^C                                                      
--- 16843009 ping statistics ---                        
3 packets transmitted, 3 received, 0% packet loss, time 2003ms                                                  
rtt min/avg/max/mdev = 4.044/4.053/4.062/0.007 ms
14

I'm probably going to get downvoted to hell but I have to ask: Can someone please explain? I'm perpetually trying to expand my knowledge on the technical side of Linux.

11

This is the behaviour of inet_aton, which ping uses to translate ASCII representations of IPv4 addresses to a 32 bit number. Its manpage: https://man7.org/linux/man-pages/man3/inet_aton.3.html

It recognizes the usual quad decimal notation of course, but also addresses of the form a.b.c or a.b, or in this instance, a, with is taken to be a 32bit number.

Each part can also be written in hex or octal, with the right prefix, such that 10.012.0x800a is as valid form for 10.10.128.10.

Not all software use inet _aton to translate ASCII addresses. inet_pton for instance (which understands both v4 and v6) doesn't

18

An IP address is a 32-bit number, usually expressed as four 8-bit numbers separated by dots. Converting 33333333 to hex we get 01FCA055; splitting that into pairs and converting back to decimal gives 1, 252, 160, 85.

2

Typically an IP address is represented as 4 8-bit integers (1.252.160.85), but it can also be represented as a single 32-bit integer (33333333). The ping utility accepts both forms.

2
lemmy.ca

interesting . . In my head, I think of ip addresses like just decimal values or integers separated by periods, but clearly a decimal value isn't processed as such by a computer. To think that IP addresses are simply strings is pretty interesting to my amateur mind, because for all my life I thought of them as technical computer jargon that isn't the same as what I used to think strings were: words!

3
remotelovereply
lemmy.ca

I don't want to go so far as to tell you how to think, but as long as we are talking about how to visualize IP addresses, you may want to check out subnets and subnet masking.

The notation of IP addresses starts to make sense when you think about the early days of TCP/IP when all IP addresses were public and NAT'ing wasn't really required yet. Basically, there needed to be ways for networks to filter traffic by IP blocks that were applicable. (It was [in part] a precursor to collision avoidance, but absolutely not the full story.) We still use addressing and masking today, but it's more obvious when it's local. (Like in data centers, where it's super practical to mask off a block of addresses for a row or rack of servers.)

To your point, yeah. IP addresses are probably more comparable to the Dewey Decimal System rather than actual numbers and thinking of them as strings is probably easier.

4

Oh no worries, I am writing a Cisco networking exam in about a month, so I've actually studied subnets and addressing a good amount, but I don't mind the refresher!

I was just speaking more generally, in terms of programming, where integers and strings are different data types, yet you can store numbers as a string, which I always found interesting.

1
lemmy.zip

Obligatory: Fuck Drake.

There are dozens of meme templates like this that you could have used instead

3
axxreply
slrpnk.net

It makes them part of the cultural Zeitgeist. And when they are already famous, it maintains their currency in that regard.

0
lemmy.world

Jesus. If you see a kid with a balloon, do you have a burning need to tell them that there was probably exploitation involved in the harvesting of the rubber?

-2

Also two random internet users in Korea and Germany, your IP addresses are blocked by mail server since I started getting phishing emails from your country.

2
needankereply
feddit.org

Yo7 block entore countries over a few fishing e-Mails?

2

I block any and all IPs that resolve outside my postal code. Support local phishing.

2