Differences

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--- infoblox_nios:dhcp [2025/05/09 07:56] – [Primary VS Secondary] bstafford
+++ infoblox_nios:dhcp [2026/03/24 21:22] (current) – [Performance] bstafford
@@ Line 18: / Line 18: @@
   * Datasheet figures for DHCP LPS are based on full DORA with no ping before offer or DDNS.
   * Reporting of actual LPS being served is based on ACKs to cover renews.
+===== Moving Leases =====
+If you update a subnet to use a different DHCP server, the existing leases will not move until they renew. If the server that issued the lease is no longer valid (because you forced it over to member2) than it shouldn't respond at the T1 timer, and should renew on the new server when it sends a discover at the T2 timer.
+If the servers are in a failover pair and you are changing the balancing, you have to wait until the MCLT expires to take effect.
 ===== DHCP Hub-Spoke =====
@@ Line 27: / Line 32: @@
 Realistically, the only other options that make any sense are 100/0 or 0/100. However, if you do this, all you are changing is the algorithm used to decide which member responds to which MAC address. The DHCP range is still shared between the two members 50/50 and that means any re-balancing will move from the 100 member to the 0 member (on a 100/0 or 0/100 configuration). This will cause a major outage.
+===== DNS Config =====
+To try and spread DNS load more evenly between two members, update the two DHCP members in the FO at a member level. On the first member, set the DNS assignment to "DNS Server 1 & DNS Server 2". On the second member, set the DNS assignment to "DNS Server 2 & DNS Server 1". So long as you don't override this at a network or range level, this means that clients using DHCP server 1 will get DNS servers in one order and clients using the DHCP server 2 will get DNS servers in the opposite order.
 ===== Failover Associations =====
@@ Line 32: / Line 39: @@
 Never rename an active failover assocation. It will trigger a recover/recover. Move all the ranges to single member then delete and recreat the FO and move all ranges to the new FO.
+===== High Availability =====
+HA should be used on at least one of the two members of a FO. Ideally, use HA on both because if a member goes down (HA makes this unlikly) then the other issues leases on MCLT.
 ===== Active-Active =====
 A DHCP fixed address in an active/active range will only apply on the box that has that part of the active/active range.
@@ Line 44: / Line 54: @@
   * Free: The lease is available for clients to use.
   * Active: The lease is currently in use by a DHCP client.
-  * Static: The lease is a fixed address lease.
+  * Static: The lease is a fixed address lease. (enable under Grid DHCP Properties, General, Advanced)
   * Expired: The lease was in use, but the DHCP client never renewed it, so it is no longer valid.
   * Released: The DHCP client returned the lease to the appliance.
   * Abandoned: The appliance cannot lease this IP address because the appliance received a response when pinging the address.
   * Backup: Lease belongs to the secondary peer in a DHCP fail over relationship.
+===== Fixed Address Lease =====
+Under Grid DHCP Properties, General, Advanced.
+Fixed Address Lease. Without this feature enabled, there is no logging of leases assigned to fixed addresses and they cannot be tracked.
 ===== Primary VS Secondary =====
 If you have a DHCP Fail-over Association (FOA), one member will be "primary" and the other "secondary". For users, it makes no difference which is which assuming that the admin is following best-practice and using balanced distribution for the FOA. MAC address hash is used to determine which server responds.
@@ Line 188: / Line 203: @@
 The new behaviour is for DHCP filters to use AND logic.
+For DHCP, you can use Option 77 (User Class Identifier). This allows you to define a "string" ID on the client (windows or Linux) and this will be passed onto DCHP server during request. The DHCP server can then use that in a DCHP Option filter to ensure only clients presenting that ID will get issued a lease. The use case would be where you have a subnet and range that needs to issue IP's normally but a specific sub-set should only be issued to a specific group of servers (e.g. Database servers). You would create a range for that use case and apply the option filter. Why would you want to do this? Possibly for creating known firewall rules.
 ===== DHCP Version =====
 NIOS uses ISC DHCP. NIOS-X uses Kea.
+The following is from NIOS 9.0.7
 For NIOS, the version of ISC DHCP is printed to syslog when the DHCP service is restarted