Chassis Redundancy and Power Budget Before a 40G Uplink Insertion
A VSP 8404C at a distribution site is populated with two MSM-8404 control modules in slots A and B, four 48-port 1G line cards, and two 1100 W power supplies. Only PSU 1 is connected to utility feed A; feed B is still being installed. The design calls for 192 access ports at 1G and two 40G uplinks, but the uplink cards have not arrived. During a maintenance window, MSM B was reseated. It boots, and 'show slot' lists it as secondary, while 'show redundancy' reports 'not ready'. The MSM B console shows 'MSM not synchronized'. Traffic is forwarding normally through MSM A. The team wants to insert the 40G cards next week and defer the second power feed until next quarter. No monitoring alerts are active.
1. What immediate risks does this chassis present, and which show commands and physical checks would you use to decide whether it is safe to add the 40G cards next week?
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The chassis is forwarding, but it has two independent availability problems. First, with only PSU 1 energized there is no power redundancy; a feed or PSU failure can remove the whole chassis. Second, MSM B is present but not synchronized, so there is no control-plane redundancy: an MSM A failure can interrupt forwarding and management. Before adding 40G cards, check 'show slot', 'show redundancy', 'show power' or 'show power budget', 'show environment', 'show fan', and 'show log'. Confirm actual PSU wattage, line-card power draw, PoE load if any, and fan tray status. Also confirm that fabric and uplink capacity support the planned 192 x 1G plus 40G. The decision should be no-go for the 40G insertion until either the second feed is live or a power calculation proves one PSU can carry the full configuration with margin, and until the MSM is synchronized or replaced.
2. Explain why 'show slot' can show the secondary MSM while redundancy is 'not ready', and what you would do to restore full MSM redundancy.
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'show slot' reports physical presence and slot role; 'show redundancy' reports whether the secondary has synchronized state and is ready to take over. A secondary MSM can boot and appear in 'show slot' while its configuration or state sync is incomplete. Check for version mismatch, failed sync, or a faulty MSM in 'show log' and 'show version'. Run the supported MSM synchronization action for the release; if it still reports 'not ready', reseat the MSM, then replace it. Do not force a failover while the secondary is unsynchronized, because that converts a redundancy warning into an outage risk. After sync, verify with 'show redundancy' and a controlled failover in a maintenance window.
3. If the second feed remains unavailable, what power-related design decision would you make about the 40G cards?
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Use the power budget rather than guessing. Add up the chassis baseline, MSMs, four 1G cards, two 40G cards, optics, and PoE. If one 1100 W PSU cannot support that with margin, delay the 40G cards or add a PSU and feed. Do not rely on a single feed as redundant just because two PSUs are installed; redundancy requires independent sources. If the business needs the uplinks, consider a lower-power configuration, fewer line cards, or a temporary chassis. Document the risk and set a date for the second feed.