<3Com> boot boot-loader flash:/Switch4500_V500R008.bin slot0 main <3Com> boot boot-loader flash:/Switch4500_V500R008.bin slot1 backup <3Com> save <3Com> reboot During reboot – watch for “Press Ctrl+B to enter boot menu” in case of failure. 4. Common Failure Modes & Recovery | Problem | Likely cause | Recovery | |--------|-------------|----------| | TFTP timeout | Firewall on PC | Disable PC firewall, use direct cable | | “Invalid file” | Wrong firmware for model | Redownload, check MD5 | | Boot loop after reboot | Corrupt flash | Boot menu → Ctrl+B → “Skip current configuration” or “Load from backup” | | No boot menu | Lost console | Power cycle, send break signal (Shift+Break in PuTTY) |

<3Com> system-view [3Com] interface vlan 1 [3Com-Vlan-interface1] ip address 192.168.0.10 24 [3Com-Vlan-interface1] quit [3Com] quit <3Com> tftp 192.168.0.100 get Switch4500_V500R008.bin Wait for checksum verification. <3Com> boot boot-loader flash:/Switch4500_V500R008.bin If two partitions exist: