Dell PowerScale Source Based Routing Guide
Mon, 17 Jun 2024 19:34:13 -0000
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Welcome to the Dell PowerScale guide on Source-Based Routing (SBR). SBR is a cool way to ensure that data packets go where they need to, based on where they came from. This part of OneFS helps set up paths for data using unique routes for each subnet. We'll cover how to set up these pathways using firewall rules and ensure the right data gets priority.
Before the introduction of OneFS Release 9.8.0.0, SBR was not enabled by default. However, with the launch of OneFS Release 9.8.0.0, SBR has been set to enabled by default for all fresh PowerScale deployments, also known as Greenfield deployments. For existing OneFS clusters, referred to as Brownfield deployments, upgrading to OneFS Release 9.8.0.0 will retain the current SBR configuration. Additionally, OneFS Release 9.8.0.0 has expanded SBR's capabilities to include IPv6 support, whereas earlier versions were limited to IPv4 support only.
Understanding how SBR works is key to taking the best network action. Though SBR changes the default route, it respects the paths you set manually. It focuses on managing the data and responding to requests, not starting them, which can really change the way data moves out of your network.
SBR Overview
Source-Based Routing (SBR) uses the source IP address of IP packets to make smart routing choices. SBR's big plus is how it handles network traffic. To put it simply, it sends return traffic back the same way it came. This reduces pressure on other routes, allowing network traffic to flow better and more evenly. This smart approach to routing shows why knowing SBR's role is crucial for network traffic.
The term Source-Based Routing (SBR) implies that it directs traffic according to the originating IP address. Yet, in practice, SBR establishes default routes specific to each subnet. SBR operates by employing designated gateways for each individual subnet.
In the absence of an SBR configuration, the gateway with the highest priority, meaning the one with the smallest numerical value that can be accessed, is selected as the default route. When SBR is activated, if traffic originates from a subnet that the default gateway cannot access, firewall rules are implemented. These rules are incorporated using IPFW.
IPFW and SBR
IPFW, also known as IP firewall, is a firewall software component of some UNIX-like operating systems and plays a key role in Source-Based Routing (SBR). IPFW acts as a firewall and can also manage routing rules. In the context of SBR, it's used to dynamically create default routes for each subnet, which are essential for directing traffic efficiently within a network.
Although SBR and firewall functionalities are both part of the IPFW table, they operate independently within different partitions of the table, allowing for separate control over each feature. With SBR, IPFW helps direct traffic based on the source IP address. If a session is initiated from a source subnet, IPFW creates a rule that ensures that the traffic is routed through the appropriate gateway.
The process of adding IPFW rules is stateless, meaning it doesn't maintain any session information. This translates to creating per-subnet default routes based on the traffic's source IP address. While SBR does not eliminate the need for a default gateway, it effectively overrides the default gateway for traffic originating from subnets not covered by static routes.
In summary, IPFW is a versatile tool that provides firewall capabilities and supports SBR by managing routing rules to ensure that traffic is directed through the most appropriate pathways within a network.
Configuring source-based routing
In OneFS, to see if SBR is configured in your cluster, use the isi network external view command, which tells you whether SBR is set to True or False:
OneFS-1# isi network external view Client TCP Ports: 2049, 445, 20, 21, 80 Default Groupnet: groupnet0 SC Rebalance Delay: 0 Source Based Routing: False SC Server TTL: 900
On OneFS 8.x and newer releases, you can use both the CLI and WebUI to configure SBR. The CLI command is:
isi network external modify --sbr=[false|true]
To configure SBR from the WebUI, navigate to Cluster Management > Network Configuration. Under the Settings tab, select the Enable source based routing checkbox, as shown here:
For more about SBR, including some important considerations, see Overview | Dell PowerScale: Network Design Considerations | Dell Technologies Info Hub.
Author: Aqib Kazi, Senior Principal Technical Marketing Engineer