Considerations for Summarization in Network Redesign
Question
In a redesign of a multiple-area network, it is recommended that summarization is to be implemented.
For redundancy requirements, summarization is done at multiple locations for each summary.
Some customers now complain of higher latency and performance issues for a server hosted in the summarized area.
What design issues should be considered when creating the summarization?
Answers
Explanations
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A. B. C. D.B.
Sure, I'd be happy to explain in detail.
First, let's start with what summarization is. Summarization is a technique used in routing protocols, such as OSPF or EIGRP, to reduce the size of the routing tables and the amount of routing information that needs to be exchanged between routers. This is done by aggregating multiple network prefixes into a single summary address, which is then advertised to other routers in the network.
Now, let's move on to the design issues that should be considered when creating summarization:
A. Summarization adds CPU overhead on the routers sourcing the summarized advertisement.
When summarization is implemented, the router that sources the summarized advertisement needs to perform extra processing to compute the summary address and advertise it to other routers. This extra processing can increase the CPU load on the router, which may cause performance issues. It is important to consider the capacity and capabilities of the routers that will be performing summarization and ensure that they have enough resources to handle the additional load.
B. Summarization prevents the visibility of the metric to the component subnets.
When a summary address is advertised, the component subnets that make up the summary are hidden from the rest of the network. This means that routers outside of the summarized area do not have visibility into the individual subnets and their metrics. This can be problematic if there are performance or connectivity issues with a specific subnet within the summarized area, as it may be difficult to isolate the problem and troubleshoot it.
C. Summarization creates routing loops.
Summarization can potentially create routing loops if it is not configured correctly. This can happen if the summary address overlaps with another summary or component subnet, or if there are multiple paths to the same destination through different summaries. To prevent routing loops, it is important to ensure that summarization is configured correctly and that the routing protocol is able to properly calculate the shortest path to the destination.
D. Summarization causes packet loss when RPF is enabled.
Reverse Path Forwarding (RPF) is a technique used to prevent IP spoofing and ensure that packets are forwarded on the correct path. When summarization is used, it can cause packet loss if RPF is enabled and the router receiving the packet does not have a route to the specific component subnet that the packet came from. This can be mitigated by configuring RPF to use loose mode instead of strict mode, or by configuring a static route for the specific component subnet.
In summary, when implementing summarization in a network redesign, it is important to consider the potential design issues such as increased CPU overhead, loss of visibility into component subnets, potential routing loops, and potential packet loss with RPF. These issues can be mitigated through proper configuration and monitoring.
