The key idea is how GSLB uses MEP to coordinate health between sites. Metric Exchange Protocol (MEP) shares health status, and the triggerMonitor setting controls when the remote site’s default service monitor runs. By setting the trigger to MEPDOWN, the local GSLB will only invoke the remote site's service monitor after MEP has marked the service as DOWN. If MEP still shows UP, the monitor isn’t triggered. This gates extra monitoring behind an MEP-down event, preventing unnecessary checks and letting the system verify the real state only when MEP detects a problem.

End-to-end security with caching and compression relies on the ADC being able to inspect and modify HTTP traffic while still keeping encryption across the full path. Terminating TLS at the ADC (front-end) lets the appliance decrypt the client request so it can cache and compress HTTP responses. At the same time, keeping the backend connection encrypted (SSL back-end) preserves encryption from the ADC to the backend servers. If the backend were unencrypted (plain HTTP/TCP), that final leg would not be secured, breaking true end-to-end protection. Therefore, using SSL on both the front-end and the back-end provides the needed visibility for caching/compression while maintaining encryption across both segments of the path.

When an active-passive Citrix ADC HA pair faces an upstream router that isn’t updating its ARP table, the traffic issue is solved by giving the VIP a stable, shared identity at the Layer 2 level. A Virtual MAC provides exactly that: a mac address that both ADC nodes can present for the VIP, so the router and switches always see the same MAC for the VIP regardless of which node is active. The active unit responds to ARP for this VMAC, and when failover occurs, the new active unit continues to respond with the same MAC. Because the MAC seen by the upstream network doesn’t change, the router’s ARP entry remains valid and traffic is directed correctly to the current active node without needing ARP updates on the upstream side. Other options relate to route or health monitoring or network configuration modes, which don’t address the ARP stability issue for a VIP in an HA pair as effectively as using a Virtual MAC does.

Filtering traffic by IPv6 addresses requires an IPv6 Access Control List. In Citrix ADC, the IPv6 variant of the ACL command is used to define these rules, indicated by the acl6 form. This ensures the rules can correctly parse and match IPv6 addresses and prefixes, which the IPv4-oriented commands cannot do. The simpleacl family exists, including a simpleacl6, but for standard, flexible IPv6 filtering you would use the acl6 command.