Content

| 5.10 |  | Troubleshooting Redistribution |
| 5.10.2 |  | Redistribution problems with IGRP/EIGRP |

IGRP has a composite metric made up of bandwidth, delay, reliability, load, and MTU. By default, it utilizes only bandwidth and delay. Other routing protocols use different metrics. For example, OSPF uses a metric based on interface cost. OSPF cost is derived from the bandwidth of the link. Cisco uses 100,100,000/bandwidth to get that cost.

IGRP does not understand the metrics of other protocols (except EIGRP) so it is necessary to input a default metric when doing redistribution.

Figure shows a network that could produce the problem in which redistributed routes do not get installed in the routing table of the receiver. OSPF is redistributed into IGRP at R1, but R2 is not receiving the IGRP routes.

R1 and R3 are running OSPF in area 0, whereas R1 and R2 are running IGRP. R3 is announcing 131.108.6.0/24 through OSPF to R1. In R1, OSPF routes are being redistributed into IGRP, but R2 is not receiving 131.108.6.0/24 through IGRP.

Debugs and Verification
Figure shows that R3 is advertising 131.108.6.0/24 through OSPF to R1. Figure shows that R1 is redistributing OSPF into IGRP. However, examining the routing table in R2, Figure shows that 131.108.6.0/24 is not being installed in the routing table.

Solution
To solve this problem, R1 needs to include the metric option with the redistribute statement, so that it can convert the OSPF metric properly. Figure shows the new configuration for R1. OSPF is redistributed into IGRP with metric values of bandwidth, delay, reliability, load, and MTU. Even if reliability and load are not being used in the IGRP metric, these values must be included in the redistribute command.

> Note: MTU is not part of the composite metric for IGRP or EIGRP, but must be included in the redistribute command.

Another solution is to use the default-metric command under router igrp. Figure shows the syntax for using the default-metric command, with the same values of bandwidth, delay, reliability, load and MTU.

The route is now installed in the routing table of R2.

> Note: EIGRP uses the same parameters with the metric option in the redistribute command and with the default-metric command. The only significant difference is that the metric is multiplied by 256 with EIGRP. Also, if the AS numbers are the same, redistribution happens automatically between IGRP and EIGRP.