One of our clients have two 6509E core switches. These switches are connected to a 3620 WAN router via a Layer 2 switch.The vlan thar makes this connection is Vlan2. EIGRP is the routing protocol. In the rouitng protocol configuration, i have passive defaulted all vlan interfaces and allowed EIGRP to run only on Vlan 2. The core switches peer with each other as well as the WAN router. Now there is another router that has to get connectivity to the LAN.This is via a wireless link. The wireless device would get connected to the branch router. At the HQ side wireless device gets connected to the topmost floor edge switch and that Vlan would be carried to the core switches. Now since this is a separate Vlan lets say Vlan 3, for EIGRP to run over this i have to give "no passive-interface vlan 3", since everything is passive defaulted. Now the concern is that in addition to core switch forming adjacency to the new branch router, the core switches would also form adjacency with eaach other via Vlan 3. So each core switch would form two adjacencies with each other, one via Vlan 2 (already in production) and the other via Vlan 3 (the new Vlan).
Now the concern is that, if this is indeed the case, will there be any effect on the network, with respect to stability of performance issues. As of the route table consists of almost 50 entries. This customer is a bank with a lot of online services and we would not like to have a situation that would cause any connectivity issues.