Issues With Link Negotiation Between the NetScreen-5GT and Cisco 3550 Switch
This article applies to ScreenOS 4.0 and higher.
The NetScreen-5GT will not be able to negotiate a link if its interface has been set to auto-negotiate and the switch interface is set to 10 Mbit/sec. Juniper Networks will only guarantee a solid link if the speed and duplex are identical for both devices. In other words, both sides must be set to either Auto, 10/Full, or 10/half duplex.
There was a bug in ScreenOS 4.0.0-DIAL2r6.3, in that the link would go up and down when both devices were set to 100 Mbit/sec full duplex. This was addressed in ScreenOS 4.0.0-DIAL2r7.3.