Chen, The behavior for connecting multiple OSPF interfaces on the same router to the same subnet is not specified. Hence, the behavior is implementation dependent. Use a LAG (IEEE 802.3ad).
Thanks, Acee On Feb 8, 2012, at 11:01 PM, Xi R Chen wrote: Hi ------------------------------ | | | eth1 eth2 | ------------------------------- | | | | -------------|----------------- | eth3 | | | ------------------------------ Did anyone test this scenario before. Assuming both eth1 and eth2 connect to eth3, eth1 eth2 and eth3 are in the same area and the same subnet (Let's say 192.168.2.0/24). From the RFC, both eth1 and eth2 are considered together to DR election cause they have same router ID. Then assuming eth2 is DR, eth3 is BDR. My qustion is: 1. What is status of eth1? Does eth1 have neighbors or adjacencies? Some documents say, in this case, all inbound traffic for the RTA will use only one interface out of eth1 or eth2. the inbound traffic to RTA is not load balanced across the interfaces. 2. The next question is, if one link fails (Let's say the link between eth2 and eth3 fails, but the interface is still active ), can the routers detect that and switch the route to ETH1? I tested it on some routers, it can not switch the route to eth1. It will set eth2 and eth3 as two separate DR, after link fails. And the status of eth1 is always backup. Which means, if I deactive eth2 (the primary interface), eth1 will turn to primary interface, establish neighborship and update the routing table. Otherwise, eth1 will always keep the backup status and not have any neighbor or adjacencies. Best Regards Chen Xi (陈希) Developer, TCP/IP on IBM i IBM China System & Technology Lab in Beijing Notes: Xi R Chen/China/IBM E-mail: [email protected]<mailto:[email protected]> Tel:(010)82450844 Address:28,Zhong Guan Cun Software Park,No.8 Dong Bei Wang West Road, Haidian District Beijing P.R.China 100193 地址：北京市海淀区东北旺西路8号，中关村软件园28号楼 邮编：100193 _______________________________________________ OSPF mailing list [email protected]<mailto:[email protected]> https://www.ietf.org/mailman/listinfo/ospf _______________________________________________ OSPF mailing list [email protected] https://www.ietf.org/mailman/listinfo/ospf
