Cisco ASR1K - 100M link issue. [SOLVED]

I was labbing today and hit one strange issue - a link between Cisco ASR1001-X (GLC-T transceiver) and Catalyst 3750 switch (100Mbps ports) was up at both sides, but CDP didn’t work, I didn’t see MAC addresses learned on the switch side. To fix an issue I had to disable auto-negotiation and hardcode 100M speed on ASR side.

interface GigabitEthernet0/0/0
 no negotiation auto
 speed 100

Even more, on Catalyst side I had to hardcode “duplex full” to get rid of duplex mismatch issue. Looks like it’s an issue with ASR or a transceivers. Anyways, it’s strange and annoying to see the link UP on both ends, but without actual connectivity:

Good luck!

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