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| 5.5 |  | Configuring EIGRP |
| 5.5.2 |  | EIGRP and the bandwidth command |

The following three rules should be adhered to when configuring EIGRP over an NBMA cloud such as Frame Relay:

- EIGRP traffic should not exceed the CIR capacity of the virtual circuit (VC).
- The aggregated traffic EIGRP has over all the VCs should not exceed the access line speed of the interface.
- The bandwidth allocated to EIGRP on each VC must be the same in both directions.

If these rules are understood and followed, EIGRP works well over the WAN. If care is not taken in the configuration of the WAN, EIGRP can swamp the network.

Configuring Bandwidth over a Multipoint Network
The configuration of the

bandwidth command in an NBMA cloud depends on the design of the VCs. If the serial line has many VCs in a multipoint configuration, and all of the VCs share bandwidth evenly, set the bandwidth to the sum of all of the CIRs. In Figure , the CIR for each VC is set to 56 Kbps. Since there are four VCs, the bandwidth is set to 224 (4 x 56).

Configuring Bandwidth over a Hybrid Multipoint Network
If the multipoint network has differing speeds allocated to the VCs, a more complex solution is needed. The following are the two main approaches:

- Take the lowest CIR and multiply this by the number of VCs. This is applied to the physical interface. The problem with this configuration is that the higher-bandwidth links may be underutilized.
- Use subinterfaces. The

bandwidth command may be configured on each subinterface, which allows different speeds on each VC. In this case, subinterfaces are configured for the links with the differing CIRs. The links that have the same configured CIR are presented as a single subinterface with a bandwidth reflecting the aggregate CIR of all the circuits. Three of the VCs have the same CIR, 256 Kbps. All three VCs are grouped together as a multipoint subinterface, serial 0/0.1. The single remaining VC, which has a lower CIR, 56 Kbps, can be assigned a point-to-point subinterface, serial0/0.2.