Will my ip changes?

[Master Disaster]

2 minutes ago, WereCatf said:

No, that is NOT how it works. DHCP is only in control of IP-address given by DHCP, it is NOT in control of IP-addresses that have been statically assigned by the devices themselves and YES, it can cause conflicts. That's how it all works. If you want the DHCP-server to be aware of all the devices, then you need the DHCP-server to assign the IP-addresses. If you want a device to always get the same IP-address and the DHCP-server being aware of it, then you set up a static DHCP-lease on the DHCP-server.

In all my years of computing I've never encountered a situation where assigning a static IP has caused any issues. So how come devices that are set to static IP still appear in the Connected Devices page of my router?

[WereCatf]

Just now, Master Disaster said:

In all my years of computing I've never encountered a situation where assigning a static IP has caused any issues. So how come devices that are set to static IP still appear in the Connected Devices page of my router?

I don't know what your router is, but there are plenty of ways devices can make themselves known, like e.g. Netbios, multicast DNS/DNS-SD service discovery etc. Linux-distros typically automatically install Avahi for that purpose, Android has a similar thing, Apple has Bonjour and so on.

[rnd42]

1 hour ago, Master Disaster said:

Heck some modern routers will move existing clients to another free address if a connecting client requests an address that's already assigned.

vs.

1 hour ago, Master Disaster said:

DHCP will never assign an address that's already in use by another client.

I seem to recognize a conflict in these two statements. But I guess that depends on the definition of "modern".

 

1 hour ago, Master Disaster said:

Its good practice to use an address thats high in the range (so 192.168.x.250 for example) as its very unlikely that IP will be in use by anything

And if it is and the router is "modern", it will start pushing and shoving to make room for the new king of the throne! A display of power and authority!

 

1 hour ago, Master Disaster said:

and once the server is connected and is requesting a static IP the router will never assign that address to another device

Unless another server is gonna come later on and request the same IP address? In which case it seems to me like we have done a full circle, and might as well just shrink the IP range for the DHCP and make our static IP assignments on the client side in the address space out of range of the DHCP server, making sure we do not assign one IP address more than once.

 

This is really just the Yang of the Yin, isn't it?

 

I mean, surely, same rules don't apply for dynamicallly (DHCP) assigned IP numbers and static (user assigned on the client, not DHCP reserved) IP numbers. Meaning I don't expect DHCP to start pushing and shoving clients that are on static IP numbers I have assigned on the client and requested from the DHCP. But it's OK for it to push and shove clients that the DHCP itself has assigned. At least that's the behavior I would expect of a modern router.

 

[Master Disaster]

1 minute ago, WereCatf said:

I don't know what your router is, but there are plenty of ways devices can make themselves known, like e.g. Netbios, multicast DNS/DNS-SD service discovery etc. Linux-distros typically automatically install Avahi for that purpose, Android has a similar thing, Apple has Bonjour and so on.

Fair enough, TIL.

[Master Disaster]

1 minute ago, rnd42 said:

vs.

I seem to recognize a conflict in these two statements. But I guess that depends on the definition of "modern".

 

And if it is and the router is "modern", it will start pushing and shoving to make room for the new king of the throne! A display of power and authority!

 

Unless another server is gonna come later on and request the same IP address? In which case it seems to me like we have done a full circle, and might as well just shrink the IP range for the DHCP and make our static IP assignments on the client side in the address space out of range of the DHCP server, making sure we do not assign one IP address more than once.

 

This is really just the Yang of the Yin, isn't it?

 

I mean, surely, same rules don't apply for dynamic (DHCP) assigned IP numbers and static (user assigned on the client, not DHCP reserved) IP numbers. Meaning I don't expect DHCP to start pushing and shoving clients that are on static IP numbers I have assigned on the client and requested from the DHCP. But it's OK for it to push and shove clients that the DHCP itself has assigned. At least that's the behavior I would expect of a modern router.

 

Turns out I totally misunderstood how DHCP works, go back and read @WereCatf's posts from the previous page.

[WereCatf]

2 minutes ago, Master Disaster said:

Turns out I totally misunderstood how DHCP works, go back and read @WereCatf's posts from the previous page.

IP-networking is a very complex thing, just try and learn how e.g. ARP is involved in it all

[rnd42]

15 hours ago, Master Disaster said:

Turns out I totally misunderstood how DHCP works, go back and read @WereCatf's posts from the previous page.

Fair enough.

16 hours ago, WereCatf said:

If you set a static IP on the device, DHCP isn't involved at all, so no.

 

15 hours ago, WereCatf said:

No, that is NOT how it works. DHCP is only in control of IP-address given by DHCP, it is NOT in control of IP-addresses that have been statically assigned by the devices themselves and YES, it can cause conflicts. That's how it all works. If you want the DHCP-server to be aware of all the devices, then you need the DHCP-server to assign the IP-addresses. If you want a device to always get the same IP-address and the DHCP-server being aware of it, then you set up a static DHCP-lease on the DHCP-server.

Whenever I have to set a static IP address on any of the clients on my LAN, I normally do that on the router, by making DHCP IP address reservations based on MAC addresses. So in this case, DHCP does get involved?

15 hours ago, Master Disaster said:

In all my years of computing I've never encountered a situation where assigning a static IP has caused any issues. So how come devices that are set to static IP still appear in the Connected Devices page of my router?

 

15 hours ago, WereCatf said:

I don't know what your router is, but there are plenty of ways devices can make themselves known, like e.g. Netbios, multicast DNS/DNS-SD service discovery etc. Linux-distros typically automatically install Avahi for that purpose, Android has a similar thing, Apple has Bonjour and so on.

I second what Master D wrote above. Do you happen to know if Avahi is responsible for this functionality on DD-WRT? I run my router on DD-WRT. This seemingly magical functionality is what's most fascinating to me, where two devices that are not supposed to be aware of each other's existence still know each other's name.

 

[WereCatf]

1 minute ago, rnd42 said:

Whenever I have to set a static IP address on any of the clients on my LAN, I normally do that on the router, by making DHCP IP address reservations based on MAC addresses. So in this case, DHCP does get involved?

That is the static DHCP-lease that I mentioned, so yes.

 

1 minute ago, rnd42 said:

I second what Master D wrote above. Do you happen to know if Avahi is responsible for this functionality on DD-WRT? I run my router on DD-WRT. This seemingly magical functionality is what's most fascinating to me, where two devices that are not supposed to be aware of each other's existence still know each other's name

You said you use DHCP, so that's why.

[rnd42]

2 minutes ago, WereCatf said:

You said you use DHCP, so that's why.

Currently, yes, I do. But before I learned that I could do it from the DHCP server, I seem to recall being able to set a static IP on a client and still see its name appear in the list of devices on the router. What kind of magic is that? Is that a thing?

 

[WereCatf]

1 minute ago, rnd42 said:

Currently, yes, I do. But before I learned that I could do it from the DHCP server, I seem to recall being able to set a static IP on a client and still see its name appear in the list of devices on the router. What kind of magic is that? Is that a thing?

I already mentioned in the earlier comment that there are plenty of various kinds of network discovery-services and all modern OSes ship with one or another such enabled and running by default. I don't use DD-WRT and I don't know your router, so I have no idea what it is running, but it sure sounds like it's also running one or another discovery-service.

[rnd42]

11 minutes ago, WereCatf said:

I already mentioned in the earlier comment that there are plenty of various kinds of network discovery-services and all modern OSes ship with one or another such enabled and running by default. I don't use DD-WRT and I don't know your router, so I have no idea what it is running, but it sure sounds like it's also running one or another discovery-service.

Fair enough. I realize it is naive of me to think that you would know what causes this magic on my router! Unless you have some kind of telesensing ability!

 

With so many different technologies at disposal, it's hard to tell. Also, DD-WRT itself comes in several different versions and editions, where they package different things, depending on the capabilities of the target device.

 

Thanks for your input!

 

[beersykins]

Yall are picky af.

 

Just logically break out a /24 into 1-99 for statics, 100-199 for normal DHCP clients and 200-254 for reserved DHCP addresses.

 

Or any other combination, it's far and away most convenient to not juggle statics for client devices, however.  The most elegant solutions blend maximum convenience.