This object sets the error metric value to announce this Level 2 summary address with, where zero indicates the metric isn't supported. Administrators use this optional metric to signal path reliability, favoring routes through more error-resistant links when other metrics are otherwise equal. For example, an engineer assigns a higher csIsisL2SummAddrErrorMetric to a summary address reachable via a known noisy legacy link, so error-metric-aware routers prefer a cleaner alternate path when one exists.