Two days spent in troubleshooting a point to point link with lot of hops between them. I stumble to see one weird thing that whenever the mux sfp port is connected to the router, the router card starts rebooting. This is the case not with a single router but with the multiple ones. We changed everything but all in vein. At last we able to catch a little point about mux which is using layer 2 switching and forwarding vlans traffic to the router directly. The broadcast was so huge which forces routes card to halt.