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

The exhibit shows an aggregate route configuration for the network172.21.0.0/22, which would summarize the specific networks172.21.0.0/24,172.21.1.0/24, and172.21.2.0/24. For an aggregate route to be active, it must have contributing routes in the routing table. If the route is hidden, it usually means there are no contributing routes that are active or the policy applied to the aggregate does not match any of the specific routes.Therefore, the first step in troubleshooting would be to verify that there are indeed active contributing routes for the aggregate to be valid.

References:

• Juniper documentation on routing policies and aggregates: Junos OS Routing Policies, Firewall Filters, and Traffic Policers User Guide

The "ultimate-hop-popping" term refers to the action taken by the penultimate router in an LSP to remove the MPLS label before delivering the packet to the ultimate router,which is not desired here. Configuring the "explicit-null" statement causes the penultimate router to replace the top label with a label that has a value of 0, which instructs the ultimate router to perform a label lookup and preserve the label switching for the entire LSP.

References:

• Juniper Networks documentation on MPLS: MPLS Applications User Guide for Routing Devices

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