How do you optimize the frequency and size of routing updates to reduce bandwidth and CPU usage?

1 Choose the right protocol

Different routing protocols have different characteristics and mechanisms for sending and receiving updates and messages. For example, distance vector protocols like RIP and EIGRP send periodic updates to all neighbors, regardless of whether there are any changes in the network. Link state protocols like OSPF and IS-IS send triggered updates only when there are changes, but they also send hello messages to maintain adjacencies. Some protocols use multicast or broadcast addresses, while others use unicast or anycast addresses. Some protocols use full or partial updates, while others use delta updates or acknowledgments. Choosing the right protocol for your network depends on various factors, such as the size, topology, scalability, and security requirements of the network.

2 Configure timers and intervals

Most routing protocols have timers and intervals that control how often and how fast they send and receive updates and messages. For example, RIP has a default update timer of 30 seconds, which means it sends a full update every 30 seconds to all neighbors. OSPF has a default hello interval of 10 seconds, which means it sends a hello message every 10 seconds to each neighbor to maintain adjacency. EIGRP has a default hello interval of 5 seconds and a default hold time of 15 seconds, which means it expects to receive a hello message from each neighbor within 15 seconds, otherwise it considers the neighbor down. You can configure these timers and intervals to suit your network needs and optimize the bandwidth and CPU usage. For example, you can increase the update timer or hello interval for stable and low-traffic links, or decrease them for dynamic and high-traffic links. You can also adjust the hold time or dead interval to match the hello interval or update timer.

3 Use summarization and filtering

Another way to optimize the frequency and size of routing updates is to use summarization and filtering techniques. Summarization means aggregating multiple routes into a single route that represents a larger network. For example, you can summarize four /24 subnets into one /22 subnet. This reduces the number of routes in the routing table and the routing updates, which saves bandwidth and CPU resources. Filtering means blocking or allowing certain routes based on criteria such as prefix, length, attribute, or policy. For example, you can filter out routes that are not relevant or useful for your network, or that are redundant or conflicting with other routes. This also reduces the number of routes in the routing table and the routing updates, which saves bandwidth and CPU resources.

4 Use compression and encryption

Some routing protocols support compression and encryption features that can help optimize the frequency and size of routing updates. Compression means reducing the size of the routing updates by removing unnecessary or redundant information, or by using shorter or more efficient encoding schemes. For example, EIGRP supports a feature called stub routing, which allows a router to advertise only a summary route or a default route to its neighbors, instead of all its routes. This reduces the size of the routing updates and the routing table of the neighbors. Encryption means securing the routing updates by using cryptographic algorithms and keys to prevent unauthorized access or modification. For example, OSPF supports a feature called authentication, which allows a router to verify the identity and integrity of its neighbors and their routing updates. This prevents malicious attacks or errors that could compromise the network.

5 Monitor and troubleshoot

The last tip for optimizing the frequency and size of routing updates is to monitor and troubleshoot your network regularly and proactively. You can use various tools and commands to check the status and performance of your routing protocols, such as show ip route, show ip protocols, show ip eigrp neighbors, show ip ospf neighbor, debug ip rip, debug ip eigrp, debug ip ospf, and so on. You can also use network management software or protocols, such as SNMP, NetFlow, or IP SLA, to collect and analyze data about your network traffic, bandwidth, and CPU usage. You can use these tools and commands to identify and resolve any issues or anomalies that could affect your routing protocols, such as misconfigurations, errors, failures, loops, flaps, or attacks.