Let’s say I have a router running both OSPF and EIGRP on different interfaces. The router has received like 10 OSPF routes from its OSPF neighbor. I want to advertise a single summary of those 10 OSPF routes to my EIGRP neighbor. I don’t want to use “ip summary-address” under the EIGRP interface because if I'm not mistaking even if OSPF fails, the router still keeps advertising that summary route to its EIGRP neighbor and becomes a black hole. So it has to be some sort of redistribution. Is it possible to summarize during redistribution? Or the only way is to have an OSPF summary route already?
you can redistribute all the routes between ospf and EIGRP and the ip summary on interface will sumarize it. the summary will be advertised only if EIGRP has routes from redistribution.