EIGRP TO EIGRP REDISTRIBUTION Anomaly

Question

Hi There
I have a situation whereby I am redistributing between 2 EIGRP instances and seeing unexpected results. I have labbed up  the scenario which is occurring in a production environment and am seeing the same results.
Please refer to the attached jpeg.
As you can see R2 is redistributing into EIGRP 30 from EIGRP 20 via a route map. R2 learns the 172.17.0.0/16 via EIGRP 20 by way of the network command on R1.
The route map on R2 references ACL 10 which has one entry access-list 10 permit 172.17.0.0 0.0.7.255
This route map does not specifically matc the 172.17.0.0/16 network however I am seeing the 172.17.0.0/16 redistributed and learned via the R3 router. I would only have expected an exact match in the route map/ACL 10 Eg. 172.17.0.0 0.0.255.255 to allow redistribution to R3 as opposed to the entry for 172.17.0.0 0.0.7.255. It is as though the route map is acting classfully and ignoring the wildcard mask
R3
R3#sh ip route eigrp 30
     172.17.0.0/16 is subnetted, 1 subnets
D EX    172.17.0.0 [170/2588160] via 192.168.10.2, 00:29:24, FastEthernet0/0
I can resolve this to achieve the desired blocking of 172.16.0.0/16 net, but was wondering if this is expected or normal behaviour
this is observed on cisco 2851, flash:c2800nm-adventerprisek9-mz.124-5a.bin ios
Thanks

Answer 1

Hi,
In my view the redistribution is performed as configured.
To achieve what you aim (if I understand it correctly) the ip prefix-list should be used instead of ACL.
You can try to modify your config as follows and see if that is what you have intended:
ip prefix-list DENY-17 permit 172.17.0.0/18
route-map DENY-17 permit 10
 match ip address  prefix-list DENY-17
Best regards,
Antonin