Configuring VLAN Interface Metrics

Normally, IS-IS metrics can have values up to 63. These metrics are narrow metrics. IS-IS generates two type, length, and value (TLV) codings, one for an IS-IS adjacency (code, length, and value (TLV) 2) and the second for an IP prefix (TLV 128 and TLV 130). During SPF, if the total cost of the path to a destination exceeds 1023, then according to ISO/IEC 10587, the path is ignored.

To overcome these restrictions, a second pair of TLVs is available, one for IP prefixes (TLV 135) and the second for IS-IS adjacency (TLV 22). With these TLVs, IS-IS metrics can have values up 16,777,215 and the maximum path metric allowed is 4,261,412,864. This allows more flexibility while designing a domain. These metrics are wide metrics.