JN0-363 Exam Dumps : Service Provider Routing and Switching, Specialist (JNCIS-SP)

Neighbors Stuck in Exstart/Exchange State The problem occurs most frequently when you attempt to run OSPF between a Cisco router and another vendor router. The problem occurs when the maximum transmission unit (MTU) settings for neighboring router interfaces do not match. If the router with the higher MTU sends a packet larger that the MTU set on the neighboring router, the neighbor router ignores the packet. When this problem occurs, the output of the show ip ospf neighbor command displays output similar to what is shown in this figure.

A mismatched Maximum Transmission Unit (MTU) setting on OSPF interfaces can cause routers to get stuck in the ExStart state. OSPF requires that both sides of a link have the same MTU to form a full adjacency.References:

• OSPF Troubleshooting, Juniper Networks Documentation
• MTU and OSPF, Juniper Networks Documentation

The root bridge in a spanning-tree network is the bridge with the smallest or the lowest bridge ID.

In the absence of a manually configured priority, the Spanning Tree Protocol (STP) elects the root bridge based on the lowest bridge ID, which is a combination of the priority and the MAC address. The device with the lowest MAC address will have the lowest bridge ID and thus be elected as the root bridge.

References

• Juniper Networks Technical Documentation on STP

When you want to advertise an interface in OSPF but not form an OSPF adjacency over that interface (for example, towards an ISP), you can configure the interface as passive. This will advertise the network on the interface in OSPF without sending OSPF hello packets or forming OSPF neighbor relationships on that interface.

References

• Juniper Networks Technical Documentation on OSPF
• OSPF Configuration Guide - Juniper Networks