Summarization

Just wondering what people thought as a best practice to balance the function of route summarization with sending unnecessary traffic to a route that is down.

For example we have:

External Network - R1 - R2 - R3

Lets say the external network has 10 networks that fall in the 192.168.x.x network range. The 192.168.x.x is used to summarize all external routes on R1, R2, and R3. Lets say for whatever reason, 3 of these networks are down. R1, R2, and R3 will still route to the summary route wasting bandwidth and potentially causing performance issues.

I only use it when going to different routing processes or protocols. The more bandwidth I have available the more networks I summarize\supernet into a larger network.

Does anyone have a best practice on when they summarize and how often the do it? I've been using my method just because it works and I don't seem to have any issues, I was just wondering if there are any guidelines\best practices more experienced vets may use

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Comments

tech-airman

gojericho0 wrote:

Just wondering what people thought as a best practice to balance the function of route summarization with sending unnecessary traffic to a route that is down.

For example we have:

External Network - R1 - R2 - R3

Lets say the external network has 10 networks that fall in the 192.168.x.x network range. The 192.168.x.x is used to summarize all external routes on R1, R2, and R3. Lets say for whatever reason, 3 of these networks are down. R1, R2, and R3 will still route to the summary route wasting bandwidth and potentially causing performance issues.

I only use it when going to different routing processes or protocols. The more bandwidth I have available the more networks I summarize\supernet into a larger network.

Does anyone have a best practice on when they summarize and how often the do it? I've been using my method just because it works and I don't seem to have any issues, I was just wondering if there are any guidelines\best practices more experienced vets may use

gojericho0,

Which routing protocol(s) are you talking about?

gojericho0

Any dynamic routing protocol

tech-airman

gojericho0 wrote:

Any dynamic routing protocol

gojericho0,

It depends.

Netstudent

gojericho0 wrote:

Just wondering what people thought as a best practice to balance the function of route summarization with sending unnecessary traffic to a route that is down.

For example we have:

External Network - R1 - R2 - R3

Lets say the external network has 10 networks that fall in the 192.168.x.x network range. The 192.168.x.x is used to summarize all external routes on R1, R2, and R3. Lets say for whatever reason, 3 of these networks are down. R1, R2, and R3 will still route to the summary route wasting bandwidth and potentially causing performance issues.

I only use it when going to different routing processes or protocols. The more bandwidth I have available the more networks I summarize\supernet into a larger network.

Does anyone have a best practice on when they summarize and how often the do it? I've been using my method just because it works and I don't seem to have any issues, I was just wondering if there are any guidelines\best practices more experienced vets may use

Actually I think hiding those single networks behind a summary route reduces the amount of overall traffic on the network. By hiding those routes, your dynamic routing protocol does not have to query, do an LSA flood, or multicast/broadcast out updates. A unicast packet that is sent to the edge and dropped somewhere in the external network has less impact on performance than routes flapping and routing protocols continually working. I would rather summarize than worry about dropped unicast packets. I summarize when ever and where ever its safe. Also if I'm only summarizing 10 routes, I wouldn;t even bother, but if I were summarizing a whole other network/entity that would greatly reduce my routing tables, I do it.

but I think this is all relative to the environment as is most things.