Describe problem in Topology:
R9 redists in its Lo0 (150.1.9.9/32) interface into EIGRP. R7 will see this as a DEX route (AD: 170). It will send it on to it's EIGRP nbors (R6/R3 and ultimately R1). R1 will redist it into OSPF. All OSPF routers will now see it as an E2 route (AD: 110). R3 will redist it back into EIGRP and R7 will now have two entries for it in its eigrp topology database.
R7 now has two entries for 150.1.9.9/32 in its eigrp topology:
155.1.37.3 (GigabitEthernet1.37), from 155.1.37.3, Send flag is 0x0
Composite metric is (3072/2816), route is External
155.1.79.9 (GigabitEthernet1.79), from 155.1.79.9, Send flag is 0x0
Composite metric is (130816/128256), route is External
The one added into its RIB is via R3 (better metric):
R7#sh ip route | in 150.1.9.9
D EX 150.1.9.9 [170/3072] via 155.1.37.3, 00:00:41, GigabitEthernet1.37
The loop can be seen if you issue a trace to 150.1.9.9 from R10 (for example):
R10#traceroute 150.1.9.9
Type escape sequence to abort.
Tracing the route to 150.1.9.9
VRF info: (vrf in name/id, vrf out name/id)
1 155.1.108.8 4 msec 1 msec 1 msec
2 155.1.58.5 1 msec 1 msec 1 msec
3 155.1.0.1 1 msec 1 msec 1 msec
4 155.1.146.6 2 msec 2 msec 1 msec
5 155.1.67.7 2 msec 2 msec 2 msec
6 155.1.37.3 1 msec 1 msec 2 msec
<and around it goes...>
Solution1: Set tag filtering on the redist points.
Solution2: Filter 150.1.9.9/32 from being advertised to R7 by R3
(etc)
