I'm currently studying for my CCIE written, which I plan to take with in the next month. I would like to share some concerns or points, that I've been pondering over the last few days, about EIGRP neighbor relationships and DUAL computations. I've attached the diagram for the Lab I've been working on, to try to understand better these behaviors.
1) In a hub spoke topology - The spokes (R1 and R2) will not form a neighbor relationship through the hub, unless the neighbor command is entered at each point of the PVC's. Only then it seems the spokes will form a relationship.
-Is this because when entering the neighbor, the Hello messages become unicast, instead of multicast? How does it compensate for TTL?
-R3 is configured with point-to-point sub-interfaces, thus they break the broadcast domain; if configured as multipoint with broadcast enabled, will it still need the neighbor command, or will it forward the broadcast and allow the spokes to become neighbors?
- Will it work if authentication is configured?
2) Bandwidth - how to calculate the correct BW and percentage in each subinterface, and the ip bandwidth-percent.
- On Frame Relay point-to-point subinterfaces BW should reflect the CIR of the PVC assigned to the subinterface. If you only have access to the DTE device and are unaware of the CIR, is there a way to show what is the CIR (Clock Rate) assigned to that PVC?
-On Frame Relay Multipoint in a hub spoke topology, BW should be calculated by ( Lowest CIR * # of PVC ). If the BW calculated exceeds the CIR of the Hub, BW should be calculated by ( Hub CIR / # of PVC ); and the (ip bandwidth-percent eigrp) command should be used to ensure 50% cap link utilization of EIGRP?
3) EIGRP Updates:
- In a Frame Relay, even if the PVC is in active or deleted, if the interface has an ip address assigned and the command no shut has been issued, the interface will show as it is in the up and up status when you issue the command #show ip int brief.
- EIGRP will start advertising those networks automatically, even if the the remote end is not active. How can this be avoided? End-to-end keepalive configuration?
Example: In the diagram if R3 is down, R1 will still advertise network 10.0.2.0, and R2 will still advertise 10.0.3.0, even though R3 is down.
All comments and insights are welcomed!