The Null interface is typically used for preventing routing loops. EIGRP, for instance, always creates a route to a Null interface when it summarizes a group of routes.
Daniel Ladrach CCNA, CCNP WorldCom -----Original Message----- From: Hunt Lee [mailto:[EMAIL PROTECTED]] Sent: Thursday, February 28, 2002 12:20 AM To: [EMAIL PROTECTED] Subject: EIGRP Question [7:36770] Hi all, I have an EIGRP question. It would be greatly appreciated if someone can shed some light on this. I found the following Routing Table from TCP / IP Vol1 by Jeff Doyle. But I don't understand why a summary route would be pointing to Null0? Jeff explains it as "this route helps to prevent potential black holes when default and summary routes are used"... which confuses me even more :( Show ip route D 192.168.16.0/24 [90/3219456] via 172.20.15.5, 00:41:41, Serial 0 C 192.168.17.0/24 is directly connected, Ethernet 0 C 192.168.18.0/24 is variably subnetted, 2 subnets, 2 masks D EX 172.25.0.0/16 [170/2221056] via 172.20.15.5, 00:41:48, Serial 0 172.20.0.0/16 is variably subnetted, 2 subnets, 2 masks D 172.20.10.0/24 [90/2195456] via 172.20.15.5, 00:41:48, Serial 0 C 172.20.15.4/30 is directly connected, Serial 0 D 172.20.15.0/30 [90/2681856] via 172.20.15.5, 00:41:48, Serial 0 D 172.20.0.0/16 is a summary, 00:00:09, Null0 Please help... Best Regards, Hunt Lee Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=36792&t=36770 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
