General

ISR1K running 17.12 and later connected to another device that runs 10M/Half combination.

Symptom

┌─────────────┐ ┌─────────────┐ │ │ g0/0/0 │ │ │ Router ├─────────────────────────────────────────┘ ISR1101 │ │ │ g0/1 Negotiation │ │ │ Duplex: Half │ │ └─────────────┘ Speed: 10 └─────────────┘ ISR 1100 Running 17.12.2 does not resolve negotiation when set to "auto" if the other side of the connection is using 10/half. Downgrade to 17.9 and earlier code resolves the auto negotiation. Example: ==============Test Router ================= Router#sh int g0/1 GigabitEthernet0/1 is up, line protocol is up Hardware is CN Gigabit Ethernet, address is fc99.4710.2c29 (bia fc99.4710.2c29) Half Duplex, 10Mbps, media type is RJ45 Current configuration : 74 bytes ! interface GigabitEthernet0/1 no ip address duplex half speed 10 end ========== ISR1K in 17.12.2 ============== Current configuration : 71 bytes ! interface GigabitEthernet0/0/0 no ip address negotiation auto end ISR1101-4P#sh int g0/0/0 GigabitEthernet0/0/0 is down, line protocol is down Hardware is C1101-1x1GE, address is 10b3.d6ad.0000 (bia 10b3.d6ad.0000) Full Duplex, 1000Mbps, link type is auto, media type is RJ45 ISR1101-4P#sh ver Cisco IOS XE Software, Version 17.12.02 =========== ISR1K in 17.9.4 ================= ISR1101-4P#sh int g0/0/0 GigabitEthernet0/0/0 is up, line protocol is up Hardware is C1101-1x1GE, address is 10b3.d6ad.0000 (bia 10b3.d6ad.0000) Half Duplex, 10Mbps, link type is auto, media type is RJ45 ISR1101-4P#sh ver Cisco IOS XE Software, Version 17.09.04a This clearly shows the problem, 17.12.2 is not resolving the auto negotiation, whereas 17.9 and older it does.

Conditions

ISR1K running 17.12 and later connected to another device that runs 10M/Half combination.

Workaround

- Hardcode Speed/duplex settings interface gi0/0/0 duplex half speed 10 - Downgrade to 17.9.x and earlier

Further Problem Description