Error 400 - the messaging layer was unable to deliver the stimulus (no replica is available)

Error 400 - the messaging layer was unable to deliver the stimulus (no replica is available)

This error occurs when there is issue with the APIC inter communication. please check if the APIC cluster is healthy.

What is Cisco transceiver QSFP-100G-FR

QSFP-100G-FR is a Cisco transceiver for 100G connectivity over single mode fibre.

Feature	Description
Form Factor	QSFP28 (Quad Small Form-factor Pluggable)
Data Rate	100 Gbps
Reach	Up to 2 kilometers
Fiber Type	Single-Mode Fiber (SMF)
Connector Type	LC Duplex
Wavelength	1310 nm

How different componet of ACI fits together

1.  VLAN Pool → defines VLANs (e.g., VLAN 113)
2. Domain → links to VLAN Pool (e.g., Physical Domain)
3. AEP → links to Domain
4. Interface Policy Group → links to AEP
5. Interface Profile → applies Interface Policy Group to a port
6. Switch Profile → applies Interface Profile to a switch
7. EPG → statically binds to the port using VLAN from the pool

Basic Vs Standard Public Ip Adddress SKU in AZURE

 Publick IP address in Azure is available in two SKUs.

Below are the key dfferences between Basic and Standard Public IP addresses.

IP Helper address in NXOS

 In NX-OS, the command equivalent to Cisco IOS's ip helper-address for DHCP relay is ip dhcp relay address. Both commands serve the same purpose: forwarding DHCP requests from clients to a DHCP server located on a different subnet.

Single-Mode Fiber (SMF) Vs Multimode Fiber (MMF)

The main difference between single-mode and multimode fiber optic cables lies in how they transmit light and the distances they can cover:

Cold Vs Warm APIC

 Unlike a Cold Standby APIC, which remains inactive and holds no data until it is promoted to active, a Warm Standby APIC continuously synchronizes data from the active APIC nodes while remaining in standby mode. This ongoing synchronization ensures that, in the event of data loss across the APIC cluster, the Warm Standby can be used to restore the cluster, even if parts of the distributed database are permanently lost.

Note - From 6.1(2), standby APIC can be setup as Warm standby APIC.