Mailing List Archive: Fits with 10gig from MX-204 to Nexus 7700

Folks,

I’ve been tearing my hair out trying to turn up a direct patch over single mode fiber using 10gig SFP+ between an MX-204 and a Nexus 7700. The MX can see the light from the 7700, and vice versa, but it never shows the interface as up. The Cisco eventually error disables the interface for flapping. Tried multiple SFPs, fibers, different ports, and the behavior is always the same. Auto negotiate on or off, speed/duplex hard coded, none of it works. Had zero issues with a different MX-204 talking to a Cisco 6832, so the issue seems to be Nexus specific.

Any hints appreciated.

—Chris
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> I’ve been tearing my hair out trying to turn up a direct patch over single mode fiber using 10gig SFP+ between an MX-204 and a Nexus 7700. The MX can see the light from the 7700, and vice versa, but it never shows the interface as up. The Cisco eventually error disables the interface for flapping. Tried multiple SFPs, fibers, different ports, and the behavior is always the same. Auto negotiate on or off, speed/duplex hard coded, none of it works. Had zero issues with a different MX-204 talking to a Cisco 6832, so the issue seems to be Nexus specific.

Just to close the loop on this for list.posterity, the issue turned out to be a dead or hung process. Apparently there’s a daemon that watches for hardware changes in the chassis configuration. That meant that the OS could never properly configure the port to bring it up. Since the router was not yet in production, JTAC recommended a reboot, which has apparently solved the problem. JunOS version 18.3R3.8.

—Chris
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