If you see the error %DUAL-6-NBRINFO: EIGRP-IPv4 xxxx is blocked: not on common subnet then it simply means that there are EIGRP devices sending multicast hellos on an interface which have a different IP Range configured to the receiving router. 160617: .Feb 22 15:11:05.194 GMT: %DUAL-6-NBRINFO: EIGRP-IPv4 34256: Neighbor 17 2.31.253.1 (Vlan43) is blocked: not on common subnet (172.31.252.1/31) 160618: .Feb 22 15:11:12.770 GMT: %DUAL-6-NBRINFO: EIGRP-IPv4 34256: Neighbor 19 2.168.205.0 (Vlan44) is blocked: not on common subnet (192.168.204.1/31) This is most likely to occur by accident when two subnets are configured on the same VLAN, with EIGRP running on the interface.
Since upgrading to the ASA5585-X firewall running in multi-context mode we have had a number of questions around functionality. We raised a case with Cisco TAC to find out why EIGRP peering is not supported between contexts. This was their response:- Thank you for your patience on this case; the behavior you are seeing on the ASA is expected since inter-context exchange of multicast is not supported “Context Guidelines EIGRP instances cannot form adjacencies with each other across shared interfaces because inter-context exchange of multicast traffic is not supported.” https://www.cisco.com/c/en/us/td/docs/security/asa/asa96/configuration/general/asa-96-general-config/route-eigrp.html#ID-2179-0000001b As a workaround, you can configure static neighbors but it is supported only on point-to-point links. https://bst.cloudapps.cisco.com/bugsearch/bug/CSCuo76566/?reffering_site=dumpcr So due to inter-context exchange of multicast traffic not being supported, EI