27 – Bis-Bis – Stateful Firewall devices and DCI challenges – Part 1 (cont)
Back to the recent comments on what is “officially” supported or not ?
First of all, let’s review the different Firewall forwarding mode officially supported
ASA cluster deployed inside a single data center:
Fig.1 Firewall forwarding mode within a single DC. Please note the firewall routed mode supported with the Layer 2 load balancing (LACP) Spanned Interface mode.
When configured in Routed mode (e.g. default gateway for the machines), the same ASA identifiers IP/MAC are distributed among all ASA members of the cluster. When the ASA cluster is stretched across different locations, the Layer 2 distribution mechanism facing the ASA devices is achieved locally using pair of switches (usually leveraged the a Multi-chassis EthernetChannel technique such as VSS or vPC).
Subsequently the same virtual MAC address (ASA vMAC) of the ASA cluster is duplicated on both sites and as the result it hits the upward switch from different interfaces.
Fig.2 ASA and duplicate vMAC address
When the ASA cluster runs the firewall routed mode with Spanned interface method, it breaks the Ethernet rules due to the duplicate MAC address, with risks of affecting the whole network operation. Consequently Continue reading




