For the S/N is: .1.3.6.1.2.1.10.127.1.1.4.1.5 (DOCS-IF-MIB docsIfSigQSignalNoise). For active modem count is depending on the vendor.
It may be helpful...
Arris C4 (soft 5.x): .1.3.6.1.4.1.4998.1.1.20.2.12.1.6
Arris 1500: .1.3.6.1.4.1.482.60.2.19.1.3
Cisco uBR: .1.3.6.1.4.1.9.9.116.1.4.1.1.5
For the S/N is: .1.3.6.1.2.1.10.127.1.1.4.1.5 (DOCS-IF-MIB docsIfSigQSignalNoise). For active modem count is depending on the vendor.
It may be helpful...
Arris C4 (soft 5.x): .1.3.6.1.4.1.4998.1.1.20.2.12.1.6
Arris 1500: .1.3.6.1.4.1.482.60.2.19.1.3
Cisco uBR: .1.3.6.1.4.1.9.9.116.1.4.1.1.5
Unfortunately SNR Up per modem does not work with Arris 1000/1500 You could only get SNR per Upstream.