IOS XR tunable DWDM XFP reports a different channel number in 'show controllers ... phy' than configured
4
On an IOS XR router (RSP-based ASR 9000 class, observed on IOS XR 4.x and 5.x), the poster configured a tunable DWDM XFP with 'controller dwdm 0/1/0/0', 'admin-state maintenance', 'wavelength 55', 'admin-state in-service' and then brought the TenGigE interface up. The running configuration shows channel 55 and the laser tunes to the right wavelength ('Wavelength Control: setpoint=1550.05 nm, error=0.00 nm'), but 'show controllers tenGigE 0/1/0/0 phy' reports 'Wavelength Channel: 30'. The poster found no caveat explaining the mismatch and asked why the reported channel number differs from the configured one.
- Hardware: Cisco ASR 9000 series router (IOS XR 4.x/5.x)
- Transceivers: unspecified tunable DWDM XFP
- Form factor: XFP
Symptoms / messages:
Wavelength Channel: 30 reported after configuring wavelength 55
Wavelength Control: setpoint=1550.05 nm, error=0.00 nm
channel number in show controllers phy differs from configuration
Comments 2
A respondent explained that the CLI 'wavelength <n>' sets an XR channel number: channel 55 maps to 193.40 THz / 1550.116 nm per 'show controllers dwdm 0/1/0/0 wavelength-map'. Software then translates that into the optic's own channel numbering (channel 30, 1550.05 nm), which is what the phy output displays, so the mismatch is only a numbering difference, not a mis-tuned laser.
The recommended practice is to configure the wavelength in nanometres with 'wavelength update <7-digit value>' (e.g. 1532290 for 1532.29 nm), choosing from the values listed by 'show controllers dwdm <port> wavelength-map'.