DHCP and address reservation

[glc650]

Not if DHCP is implemented properly. Both server and client have mechanisms for detecting IPs that are already in use.

[xxx (Banned - toxicity)]

Enlighten me. What do you mean by ‘implemented correctly’ and wouldn’t that be the responsibility of the router software and, in this case, Apple?

[glc650]

If you look up how DHCP works you will see that the server uses ping while the client uses ARP to check for IP availability. As with BCBC, I don’t recall ever seeing an issue with IPs from the DHCP scope being statically assigned and most home users wouldn’t give this a second thought. That said, I’ve always advised users to use a DHCP reservation as that way they can get a full accounting of IP allocation by looking at the router’s UI (and avoid a user trying to assign the same IP twice which is more likely than DHCP doing so).

[xxx (Banned - toxicity)]

@glc650

If you look up how DHCP works you will see that the server uses ping while the client uses ARP to check for IP availability

And yet, there are collisions. At least, problems on this forum have been cleared up by removing static addressing from the device and assigning reserved addresses in the router.

Dunno, I prefer to use the router method.

[glc650]

That would be on the client or server implementation then assuming the conflicts where caused by DHCP and not a user trying to use the same IP twice.

[xxx (Banned - toxicity)]

I guess then that advice like this and other similar articles are misleading?

When IP Addresses Collide

I suppose this is a key section.

If a device disconnects from the network and later reconnects, the DHCP server might give its address to another device while it’s away, and then the device’s address will change when it rejoins the network. This isn’t a problem unless it tries to resume a previous session. In that case it may have to restart the session

Still, I stand by my and (evidently) your qualified advice.

[glc650]

I see nothing in that “article” that shows the author has an understanding of how DHCP works (quite the opposite). With the number of junk consumer/wifi routers out there I wouldn’t be surprised if there were issues as you suggest and as I mentioned above I prefer reservations myself anyway (for other reasons) and advise others to use them for the reason I mentioned above.

[Martin_Webster]

@glc650, I have moved this discussion to a new thread as it doesn’t provide assistance to the OP.

[xxx (Banned - toxicity)]

@glc650

I see nothing in that “article” that shows the author has an understanding of how DHCP works (quite the opposite)

Please point me to an article, if you can offhand, so that next a discussion like this occurs I can either agree or refute. Thanks.

[Martin_Webster]

@glc650

That would be on the client or server implementation then assuming the conflicts where caused by DHCP and not a user trying to use the same IP twice.

If a device isn’t always on, and its static IP address is in the range reserved for DHCP clients, it is inevitable that the address will be reused at some point.

When fixing the IP on the client, do so using an address not used by DHCP.

[glc650]

Generally, something that requires a static IP is always on but that’s a good point.

[CrystalGipsy (Resisting the flow!)]

Address reservation is just easier and if you switch routers at any point it won’t stop the device from connecting to the new network because it has a fixed ip that isn’t in the range on the new network, this has happened to tons of users fixing ip on the core itself. As Martin has said if you insist on fixing on the device it’s best to stick to a range of ip addresses outside of the DHCP pool, but you would have to limit the pool on the router to do this, not all routers allow that level of tinkering if from an ISP.

[wizardofoz (Mr Fix It aka The Wiz)]

Unless you are well experienced in networking best to stick with dhcp and address reservations as noted above