Selective ARP Proxy for VM Migration Stability
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Solution Overview
Problem
In virtual private networks (VPNs) connecting multiple sites, the oscillation of default gateway MAC addresses during virtual machine migration leads to traffic interruptions due to the need for consistent IP addresses, causing network instability and potential traffic failures.
Innovation Solution
Implementing a managed forwarding element (MFE) at each site to selectively proxy Address Resolution Protocol (ARP) requests, ensuring that only ARP requests for data compute nodes using a distributed logical router as a default gateway are proxied, thereby maintaining consistent IP routing without reconfiguration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the default gateway IP address remains the same before and after VM migration to ensure proper routing, then the VM can migrate without reconfiguration, but the learnt gateway MAC address oscillates between different MAC addresses of multiple default gateways causing traffic interruptions
Solution Approach 1:
The patent introduces a distributed logical router as an intermediary component that mediates between the VM and the physical default gateways. This logical router maintains a consistent MAC address across all sites while allowing the underlying physical gateways to have different MAC addresses, thus preventing MAC address oscillation and maintaining network connectivity stability during VM migration.
Solution Approach 2:
The patent segments the networking function into two distinct layers: a stable logical networking layer (distributed logical router with consistent MAC address) and a physical networking layer (multiple default gateways with different MAC addresses). This segmentation allows the logical layer to provide stability for VM migration while the physical layer handles site-specific gateway variations.
2Reliability
If ARP requests are proxied for all DCNs to maintain routing consistency, then IP traffic is properly routed during migration, but unnecessary ARP proxying increases network traffic and processing overhead
Solution Approach 1:
The patent applies local quality by making the ARP proxying behavior context-dependent rather than universal. The MFE checks whether the destination IP address in an ARP request belongs to a DCN that uses the distributed logical router as its default gateway, and only proxies the request if this condition is met. This selective approach reduces unnecessary ARP proxying and associated overhead while maintaining routing consistency for relevant traffic.
Data Source
AI summary
Some embodiments provide a method for proxying ARP requests. At an MFE that executes on a host computer operating at a first site to implement a distributed router along with at least one additional MFE at the first site, the method receives, from a router at a remote second site, an ARP request for an IP address associated with a logical switch that spans the first site and the remote second site, and to which both the distributed router and the router at the remote second site connect. The method determines whether a table that includes IP addresses for a set of DCNs that use the distributed router as a default gateway includes the IP address. When the IP address is in the table, the method proxies the request at the host computer. When the particular IP address is not in the table, the MFE does not proxy the request.