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  • Zoran Jankov wrote:

    OK, but why would you rather use static IP configuration locally on every server? What is the benefit over DHCP reservations, or rather, what is the down side of using DHCP reservations?

    No benefit at all.

    Size matters - if you only have 2 servers then it makes no sense, but as the number of servers increases use DHCP. Critical infrastructure needs static (dhcp server, AD domain controller) but all others DHCP. This is the default practice in enterprise and hosting. IT is flexible when VMs move, servers are replaced etc. Servers need to be on a different subnet to users, dhcp leases should be long e.g. 30 days and ideally dhcp scope resilient.

    I've not seen an environment with more than 20 servers use static for a decade and reservation use is dwindling - everything should use dns name so no issues. Only use reservation if firewall or other device needs to reference the host and it's name resolution feature is not suitable.

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    • Unless the range is tiny, I wouldn't bother setting ranges for things like your servers.

      Everyone works different, but I find having a static IP lets you ping things to check they're running or reachable, and having a map for your servers so you know exactly what IP is what at all times is extremely beneficial in several cases.

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    • It is a good practice to set servers with an static IP address, I would not use a reservation for a server, I rather those to be solid static, however, if you will use manually assigned static IPs, be sure to either use IPs out of the range of IP in use for the DHCP distribution scope, or exclude them from the distribution range.

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    • OK, but why would you rather use static IP configuration locally on every server? What is the benefit over DHCP reservations, or rather, what is the down side of using DHCP reservations?

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    • Zoran Jankov wrote:

      OK, but why would you rather use static IP configuration locally on every server? What is the benefit over DHCP reservations, or rather, what is the down side of using DHCP reservations?

      So that you instantly know exactly what each server IP address is at any given time, you can remote on quicker, or see what they are doing. if it is any number in a range EG. 192.168.1.1 to 192.168.1.10, then you'd waste time trying to check what the IP is.

      Imagine your fileserver is on .2 one week then .7 the next week and you have some software that breaks if it's changed etc.

      What is the benefit of using DHCP reservations for servers?


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    • In my original post I esplaned what is the benefit of the using DHCP Reservations. Regarding your concerns in your previous answer read the following:

      DHCP Reservation 

      A DHCP reservation is a permanent IP address assignment. It is a specific IP address within a DHCP scope that is permanently reserved for leased use to a specific DHCP client. Users can configure a DHCP reservation in their DHCP server when they need to reserve a permanent IP address assignment. Reservations are used for DHCP enabled devices like print and file servers or other application servers that always have the fixed IP address on the network.

      Source: DHCP Reservation

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    • Stepping back, I would say that your DNS server IP addresses should never have changed in the first place. We have replaced DCs about 50 times in my organization. Every time the new DC took the IP address if the DC it replaced. Therefore everything with a static DNS server could use the same settings, as well as all of the DHCP scopes could remain exactly as they were before.

      DHCP reservations are fine for servers. About the same amount of work as setting static IP. Nothing handed out by DHCP should change over time though. Just be sure that your DCs always boot first. You could have issues powering on the environment after a total shutdown if servers are on DHCP.

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    • I don't use reservations for my servers, I like to have them with static IP addresses.  It's really just personal preference.  But, I do use reservations for printers and other devices that I want to have a consistent IP address without the hassle of manual configuration at the device.

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    • Zoran Jankov wrote:

      I had a job of creating four new domain controllers and two new separate DHCP servers, and demoting those three old domain controllers.

      • How many sub-nets does your organization have, in order to use 6-9 DHCP servers?
      • Do they all use different, non-overlapping scopes?
      • Or how many are configured for fail-over?

      Zoran Jankov wrote:

      I was wondering if it is better to use DHCP reservations for servers and computers that must have static IP address?
      No, definitely not  better. If your network is so large and complex that you need a single place for managing these, you might consider to use an IPAM solution. Reservations for servers could be a workaround for some limitations of (prosumer) routers for small businesses.
      • Of which DHCP server shall the first booting DHCP get its IP address if he can't use a static IP address when you boot all servers, e.g. after some power outage?

      Zoran Jankov wrote:

      What am I missing?

      You missed the use case when your whole infrastructure is booting and hence no IP addresses assigned, then no DHCP server will yet be available too, hence resulting in APIPA or link local IP addresses.

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    • scheff1 wrote:

      • How many sub-nets does your organization have, in order to use 6-9 DHCP servers?
      • Do they all use different, non-overlapping scopes?
      • Or how many are configured for fail-over?
      • Of which DHCP server shall the first booting DHCP get its IP address if he can't use a static IP address when you boot all servers, e.g. after some power outage?
      • Maybe I was not clear enough. My previous company has only two DHCP server, a frist they whre on the domain controlers, and later I separated them by creating two new ones. The roles are now seperated, and this configuration is now future proof and future DC and DHCP server replacements will have the same IP addresses and names.
      • There are about 200 DHCP non-overlapping scopes.
      • The two DHCP servers have all DHCP scopes in failover relationship in 50/50 load balanced mode.
      • DHCP servers can have statically assigned IP addresses, maybe even domain controllers, but not all other 300 servers, and some other approximately 1000 devices that must have static IP addresses

      I will research on IPAM solutions you mentioned. Do you have any concrete suggestions?

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    • Spicy Joseph wrote:

      Zoran Jankov wrote:

      OK, but why would you rather use static IP configuration locally on every server? What is the benefit over DHCP reservations, or rather, what is the down side of using DHCP reservations?

      So that you instantly know exactly what each server IP address is at any given time, you can remote on quicker, or see what they are doing. if it is any number in a range EG. 192.168.1.1 to 192.168.1.10, then you'd waste time trying to check what the IP is.

      Imagine your fileserver is on .2 one week then .7 the next week and you have some software that breaks if it's changed etc.

      What is the benefit of using DHCP reservations for servers?


      I manage many sites with Active Directory, DHCP services, DNS, etc., yes I can tell you the IP of each of the servers at every location. Maybe us old school people do things in a different way, but I never had issues with servers where I assigned an static IP manually because the DHCP server was down. I use reservations for many devices in the network, wireless access points, printers, traffic counters, in retail environments, TVs, and certain computers, but for servers I always use a manually assigned IP address.

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    • There also the case of setting up a box with multiple IP's, I want those IP's in sequence, if I do it by DHCP reservation, I have no real control over what IP gets assigned to what nic.

      I also leave gaps in my IP ranges for expansion so that I can keep IPs of server clusters sequential. With DHCP you're won't have any organization.

      You can do it, there no reason why it wouldn't work, I just wouldn't consider it best practice.

      It would also be a hassle if your DHCP server isn't working and your servers reboot and can't get their IP back.

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    • I use static addresses on all servers, switches, printers.  Very rarely do I use a reservation for anything.  Only times I really recall using them is long ago for a few designated PCs for special software and even then just assigned a local static when the time came to replace the pc.  Was just as easy to assign a static on the PC than update the MAC in the DHCP config.  

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    • There three benefits (one of which is admittedly small) of using static addressing directly on the server as opposed to a DHCP reservation:

      1. At least the DHCP server must have a static IP.  Otherwise, there will be no DHCP server for the DHCP server to get an address from.  

      2.  If the DHCP server fails, machines with static IPs can still be rebooted and continue to function.  If they are using reservations, they would not be able to get back online.  Again, if you have physical access this is fine, but in a fully remote situation you would lose the ability to control the device as it would be knocked offline.

      3.  (The admittedly small benefit)  When starting up, a server with a static IP hard-coded does not have to reach out to a DHCP server.  There is minimal bandwidth savings.  Over a LAN it won't matter much, but over VPN links it might be something that becomes more significant.

      I hope this helps.

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    • mrsleep wrote:

      There also the case of setting up a box with multiple IP's, I want those IP's in sequence, if I do it by DHCP reservation, I have no real control over what IP gets assigned to what nic.

      I also leave gaps in my IP ranges for expansion so that I can keep IPs of server clusters sequential. With DHCP you're won't have any organization.

      You can do it, there no reason why it wouldn't work, I just wouldn't consider it best practice.

      It would also be a hassle if your DHCP server isn't working and your servers reboot and can't get their IP back.

      DHCP reservations are done according to MAC address, so you can absolutely control what IP gets assigned to which NIC.

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    • Zoran Jankov wrote:

      OK, but why would you rather use static IP configuration locally on every server? What is the benefit over DHCP reservations, or rather, what is the down side of using DHCP reservations?

      No benefit at all.

      Size matters - if you only have 2 servers then it makes no sense, but as the number of servers increases use DHCP. Critical infrastructure needs static (dhcp server, AD domain controller) but all others DHCP. This is the default practice in enterprise and hosting. IT is flexible when VMs move, servers are replaced etc. Servers need to be on a different subnet to users, dhcp leases should be long e.g. 30 days and ideally dhcp scope resilient.

      I've not seen an environment with more than 20 servers use static for a decade and reservation use is dwindling - everything should use dns name so no issues. Only use reservation if firewall or other device needs to reference the host and it's name resolution feature is not suitable.

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    • I only ever use static.  I want to know where the thing is at all times, and if something changes, I don't want to have to hunt it down and get it back to the way it was. 

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    • Scott4074 wrote:

      I only ever use static.  I want to know where the thing is at all times, and if something changes, I don't want to have to hunt it down and get it back to the way it was. 

      That should never be a problem with DHCP reservations. That's why they exist.

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    • I use both Reservations and Static IP addresses. 

      Most Static IP on servers, and reservations on a few workstations that need them.

      Using the reservation option, it allows the device to show up in your DHCP list, so other techs that may be working things find it easier to locate all workstations without the need of scanning the subnet, or looking them up on a spreadsheet.

      I used to work at a large organization, supporting multiple offices.  the help desk handled all the Tier 1 calls and it was easy for them to look in the DHCP scope for the office to help locate machines IP. (I know there are lots of other ways you can find this information out, but for new techs, it was the quickest and easiest way for them to see what all is on the network) so reservations helped out a lot.

      I have not had any issues using reservations, but like I said, manly used for workstations and make it know to the rest of the department what block of IPs are setup aside for servers static addresses.

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    • kevinmhsieh wrote:

      Scott4074 wrote:

      I only ever use static.  I want to know where the thing is at all times, and if something changes, I don't want to have to hunt it down and get it back to the way it was. 

      That should never be a problem with DHCP reservations. That's why they exist.

      Doesn't matter.  If I set something, I want it to stay set.  I want to know that today, tomorrow, ten years from now, ten decades from now, if somebody needs to access the thing, it is where it's supposed to be.  I've dealt with enough technology that you set and then it suddenly decides to change its settings two years on and there's no reason why other than it's junk.  It works and it works well.  That's all I need to know.  

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    • Zoran Jankov wrote:

      I will research on IPAM solutions you mentioned. Do you have any concrete suggestions?

      No, I don't remember. I never deployed nor managed any IPAM solution. But I know that such solutions were used at least in two large corporations I already worked at. And one of them also mentioned the name of the solution. But as I just wrote, I don't remember the name of that solution used. Such provisioning was happening once per night.

      Zoran Jankov wrote:

      What are the problems when using DHCP reservations, if there are any?

      I forgot to mention another problem with DHCP reservations. With these, you can only assign a single IP address per NIC while with static IP addresses, you may assign several IP addresses per NIC. At least I don't know how to assign more than one IP address per NIC.

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    • In most situations DHCP reservation is always the go to unless a device plays a hugely important role. By setting a local static IP you're basically skipping the time that the server takes to reassign in some events such as a power outage. It will always just be that address and nothing will ever take that place. You're just making it more efficient with local assigned static IP. This is why you sometimes do this with printers as well.

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