/31 Subnet - Everything You Know About Subnet Masks Is Wrong
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- เผยแพร่เมื่อ 27 พ.ค. 2019
- Not everything! But, do we need four addresses for a point to point? Most modern day classes teach you that you can't use the first and the last addresses.
Have you been wasting IPs using a /30 subnet on your point to point WAN links? Let's change that!
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Love to see a full subnet primer Willie, as always such educational content
this is covered in RFC 3021. /31 has different behavior for anything that supports RFC 3021; which is most modern devices. So this is expected behavior for anything that supports the RFC for it. anything that doesn't should give an error when you put in the subnet mask for /31.
Thank you for providing reference ❤
Please do a full subnet video. Also a Vlan video with switches, tagging, trunks and etc would be great as well. Thanks for all you do!
RFC 3021 is quite old, it was adopted on December 2000 (19 years ago), even if it took some time to be adapted into devices, and even more time for said devices to be actively running in networks, I believe it's been at least 10 years that every devices should be compliant :)
Thelvaen Mandel rfc 3021 is 20yo and is still a proposed standard. So safe to assume that it won’t change again for another 20 years. As such many vendors won’t spend the r&d to adopt it. Considering that IPv6 is upon us now.
As an instructor at a local Comm College, I know have to change my sub-netting instruction. Great video as always. You always make me smarter. Keep up the great work.
+1 for the subnet primer, show us all that you know about subneting!
Thanks for all you do!
/30 is very popular and /31 is not because it’s not supposed in all devices. Learn that trick when I was working at ISP.
Yup. Testing an unusual configuration on a pair of identical devices proves nothing. It works on the EdgeRouter with that particular firmware revision. There's no guarantee it will work with future updates, much less other Ubiquiti devices or devices from other manufacturers.
Yes... please upload a Full Subnet, Willie... Great video!
That new intro is super nice! Thanks for these good video’s! Been here since the beginning and awesome seeing your channel grow step by step!
would love to see a full subnet primer!
Thank you Willie for explaining the subnet primer.
Full subnet primer? Yes please!
Cox fiber uses /31 addresses. I have a few in use today
Would be great to see a full subnet video
Subscribed and loved this video. Yes please, a small bite sized series on subnetting would be fantastic. (I really appreciate your short, to-the-point style!). Yes, as mentioned elsewhere, amazing intros. Do a video about them too! Oh, one thing. Use cases for this and whatever you publish about subnetting, with of course the understanding that a use case is not a hard and fast definition of "only use for" ;-) ... It will help me as a noob ;-)
We have been using /31 for P2P for some time, in fact I believe it has been adopted way before 3021 as there as always been links that cant handle broadcast, like ATM F/R or other serial based devices. I think this has also been adopted into IPv6, but there are cases where this had gone really bad (/64 for point to point)
Hey Willie, this Intro is best every you had.
What is ammo in the background? (CRTG)
Second time watching this video in three months because it's a great refresher. Thanks!
Great...tks from Lisbon - Portugal
Willie that was amazing. You just did in 5mins what Cisco would have taken 3 weeks, two modules, 10 videos...etc to explain. let alone the fact that you used UBNT, displays great maturity in remaining vendor neutral. Also demonstrating that its not a cisco proprietary protocol.
Would there be any problems if you advertises the /31 sybnet? Would other non edge routers have any problems agreeing to the protocol?
Yes, please do a full subnet video.
I'd love to know more about subnets
You should explain spanning tree too
Hi
Can you do video about USG to USG over the internet not same control using VPN and i want another side see only one IP in my side us
Thank you
This was great. Thanks for the info.
Yes please on the subnet primer
what about /32 Can you make another video explaining when can we use a single address ?
Do you have a bigger board like one attach to some type of wall?
Very helpful. Also, a big white board might be helpful, so we can see the whole process.
I have done this on Cisco IOS 15.x & IOS-XE and it works fine on a point-to-point link.
we use these all the time on cellular backup WAN connections
Very good. I've just learned something new. Thanks
254 is pretty common on a wan interface when a single public IP is provided.
I am new to subnetting and I have a question, so does this mean that a ton of /31 are available and never get used since most companies and the public uses all of the other prefixes?
If you have a /24 you can divide it into a bunch of /31
Please upload full subnet video.
im helping a friend swap a cisco for a udm se and im not sure how to configure it for wan but the isp says its /31
Do a full subnet primer please
If you’re taking video requests, I’d love to see a full ipv6 video. I’m solid on ipv4. I would really love to see it setup on an edgeroutet/edgeswitch.
Interesting. Thank you very much for this video.
I started watching this to understand what a subnet mask was, but halfway through I still didn't have a clue what you were talking about.
Thanks for the video!
Really need a sub net primer.
I subbed because this channel will help with my Cisco
Definitely do a subnet video.
But I want to also see more IPv6.
People want more subnet videos, but in the same sentence they want v6 videos... Yeah, learn subnetting on v4 110% before going v6, its complicated enough.
@@jmkhenka I have IPv4 subnetting down. I'm catering to multiple skill levels here. Other people could use Willie's way with words explaining IPv4. Others, like me, need help with the more advanced IPv6.
@@wiz722 If you know IPv4 subnetting, then IPv6 is a lot easier. You can afford to give out a lot of IP addresses per subnet because there are billions available. I've seen Point to Point links use /64 address space! wasteful but it doesn't matter! :)
you need big whiteboard willie.
Thanks
go for the "full subnet" video .
I would like to see a Full clan and subnet primer
Shouldn't you need to use a cross over cable for this to work? Not a standard patch cable?
A lot of devices nowadays automagically detect the type of cable and adjust the pins dynamically. The need for crossover cables nowadays has largely been rendered moot.
Auto-MDI-X ports.
You can do it the old fashion way with straight utp cables and cross utp cables.
But you want run into such situations anymore.
In the scenario where there are 2 equal devices for example 2 switches you would use crossover utp cable.
Why is this?
Because think of it like a road, they drive on the same lane with a straight and bumb into each other if they are equal devices.
That is why the cross is used on equal devices so they each use their own separate lanes for their cars.
If unequal they always use other lanes as their opposite partner device, so a Straight cable would be needed to connect them.
Important to know that /31 for p2p interfaces is not a ratified standard and therefore not supported by all vendors. When doing this in mixed environments do your homework.
Yeah there's nothing wrong with using the 31 mask. I do it all the time.
For my it' is bad habit... ;P
Works well in Cisco equipment. Does not work with Juniper.
@@samsampier7147 It definitely works on Juniper equipment. I've done it many times
What model and code? We tried that many times in our equipment, SRX 200 Juniper IOS 9 and it rejected the commit.
@@samsampier7147 It works with All models. Junos 9 is extremely old. You really need to upgrade.
Please use a full size white board.
/32 works with interesting effects . . .
great stuff
Subnet for beginner or for dummies
Also helps with security because yo can only use 2 devices on that subnet. So, in theory, no third device can participate on that LAN on the same subnet.
Nice t-shirt
Cool trick! Feel like it depends more on manufacturer implementation than network theory in practice though
I just wanna know what the bullets are for.
But you didnt cover /32 on wan point to point link.
LetsSmash007 because it wouldn’t work. That’s a single address.
Uendar karplips thank you, brain melting in the middle of OSPF 200-205, this book started labeling one side of a P2P link with IP/32 and the other side as IP/30. Without prior explanation if caused me to think what the hell.
can you draw a real world diagram for a use for that?
is that for a LAN network or WAN to WAN
You have to control both sides of the connection. In most WAN topologies you don't have control, the next hop router is not part of your autonomous system. If you do control both devices the only limitations is software and what version of code.
R M, this is for either a point to point wireless link or a wan connection, if you don’t need a broadcast you will not need to use a /30
What’s the benefit of this though?
Less wasting of address space for something that is not needed
@@fl0r1svdk Nothing is "wasted" you can assign local class Cs all day long and no one cares. haha
@@HisLoveArmy Classfull networking is not used anymore. Also all this applies to public address space too.
Also helps with security because yo can only use 2 devices on that subnet. So, in theory, no third device can participate on that LAN on the same subnet.
less devices, less broadcasts, less multicast traffic
I have a client who has 2 offices at different locations. 1st Office uses a Comcast Router. 2nd Office uses an ATT router. I would like to find out how to set up a static Point-to-Point route between each office so that I can have both networks appear as being on the same network without using VPN, If possible. Could you should how this could be done using the gateways provided from the ISP's and no 3rd party router? I know how to set the gateways into bridge mode and then just use a 3rd party router at both locations, but I want to see if it's possible to set this up using only what the ISP's provided? If possible? Thanks
@David Beem the reason is because the end users are not too bright and they''ll be calling me for months on how to VPN into the other office network just to save a file on the server through a mapped network drive. Or they'll be trying to access the mapped network drive and end up getting an error because they didn't remember to log into the VPN first.
So I wanted to see about connecting up a static route between the two locations to make the networks appear as if they are on the same network without the end user needing to intervene,
@@berniecruz8405 what you need is a site-to-site VPN. Your end users will not interact with it. Never should you route your internal traffic over the Internet without a VPN.
@@thebigmacd Thats right! Forgot all about that! But I don't think the ISP gateways are capable of doing this task. Or are they?
I'm trying not to have to have my client buy more stuff if it's not necessary.
@@berniecruz8405 site-to-site VPN would have to be done with your customer's own equipment I'm afraid.
@@thebigmacd Yeah that's what I was thinking as well.
I would love a full subnet primer.
Sadly Packet Tracer is shite and doesn't support /31s for point to point addresses.
RFC 3021 👈
128+64+32+16+8+4+2=254
Could of been explained in 2 minutes. Mostly a lot of fluff to fill up viewing time for youtube analytics.
Local man ruins the IPv4 distribution industry in 10 minutes
Dumb title .... this only works on certain hardware / software and it doesn’t change anything I already knew about it subnetting ...., thumbs down.