If for some reason one of the routes fails that is being summarized, the packet will match the summary to null 0 and be dropped. This is a safety mechanism so the router doesn't waste cycles on packets it can't route.
""Hunt Lee"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > When using EIGRP Summary: > > On the router that performs the summarization, it's routing table will have > entry listed as Null0 for the summary routes > > And on the downstream routers, their routing table will only have the > summaries - no reference to Null 0. > > However, the following paragraph is what I'm confused about:- > > By applying the longest match rule, the downstream routers will forward all > destination prefixes using the summary address. Eventually, these routers > will be forwarded to the router performing the summarization. The > summarizing router will match the destination prefixes with their longer > matching subnets. If any of the destination prefixes match the summary > address only, the summarizing router will forward these packets to the null > interface, and they will be discarded. > > But why / when would the destination prefixes match the summary address > only?? > > Any help will be greatly appreciated. > > Best Regards, > Hunt Lee > IP Solution Analyst > Cable & Wireless Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=31264&t=31256 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
