Question about summarization IP's

steele84

Hello, I'm doing some written labs from lammel's text for ICND1 (written lab 5.1) I came across a dilemma where I can't figure out what cisco's best practices would be. I'm to summarize subnets 192.168.1.0 - 192.168.12.0 and I know that I could easily do it with a block size of 16, but I thought I read that it is not a good idea to have empty networks being summarized in a summarization IP for fear that they might pop up in the network outside that summarization zone. So I went with a block size of 8 and would assume that the 5 networks would have to be added to the routing table. I'm I off on this thinking or where do I draw the line in deciding what to allow in my summary zone ? Thanks

james43026

192.168.1.0 - 192.168.12.0 Well you have multiple options to summarize this. Best practices would be to either summarize it with 192.168.1.0 /29 and 192.168.1.8 /30 and 192.168.1.12 (advertised individually) advertised, or with 192.168.1.0 /29 and the rest of the networks would be advertised individually. As you stated you would never want to summarize networks, and have networks included in that summary that aren't actually where the route would point them.