NQA for Static Routes
As mentioned previously, static routing does not have a dedicated fault detection mechanism. If a fault occurs, the corresponding static route will not be automatically deleted from the IP routing table. This can interrupt services for a significant amount of time. The network administrator must delete the corresponding static route to allow traffic to switch to an available path.
An effective method is required to detect faults in links related to static routes. BFD for static routes is applicable only to the scenario where both communicating devices support BFD. If either of the two communicating devices supports NQA, NQA for static routes can be used to detect faults in links where Layer 2 devices reside.
- If NQA detects a fault in the link, the system sets the static route to inactive. The route becomes unavailable and is deleted from the IP routing table.
- If NQA finds that the link recovers, the system sets the static route to active. The route becomes available and is added to the IP routing table.
For details about NQA, see "NQA Configuration - Principles" in the Configuration Guide - Network Management and Monitoring.
NOTE: When a static route is associated with an NQA test instance, only ICMP test instances are used to test whether there are reachable routes between the source and destination.
Each static route can be associated with only one NQA test instance.
Applications
On the network shown in Figure 2-1, each access switch provides access services for 10 users, and a total of 100 users are connected to the network. Because dynamic routing protocols are unavailable for communication between RouterB and users, static routes are configured on RouterB. For network stability, RouterC, functioning as the backup for RouterB, is configured with static routes to the same destination. RouterA, RouterB, and RouterC run a dynamic routing protocol to learn routes from each other. RouterB and RouterC import static routes using a dynamic routing protocol and have different costs for these static routes. After the configuration is complete, RouterA can use the dynamic routing protocol to learn routes destined for users from RouterB and RouterC. RouterA uses the link related to the static route with a lower cost as the active link and the other link as the standby link.
NQA for static routes is configured on RouterB. NQA tests are performed to check the active link of RouterB → SwitchA → SwitchC (SwitchD). If the active link fails, the corresponding static route is deleted from the routing table, and traffic diverts to the standby link of RouterC → SwitchB → SwitchC (SwitchD). If both links work properly, traffic travels along the active link.
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