To verify the status of the tunnel from R1, you would issue a ping from the source address that is assigned to R1's end of the tunnel. In the exhibit, we can see that the tunnel interface (gre-0/0/0.0) has the IP address 198.51.100.1 on R1. Therefore, to test the tunnel's status, you should ping the IP address at the other end of the tunnel (which is likely the address on User B's interface or another interface on R2) from R1's tunnel source address.

References:

• Juniper Networks documentation on GRE: GRE Interface Configuration

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

In the given exhibit, interfacege-0/0/0is configured to accept VLANs 101-120 andge-0/0/1is configured with flexible VLAN tagging, which means it can tag traffic with any VLAN ID specified. However, only VLAN 200 is explicitly mentioned forge-0/0/1.A. Traffic tagged with VLAN 101 will pass throughge-0/0/0and will egress onge-0/0/1with the same VLAN tag, because the VLAN ID is within the allowed range on both interfaces.B. VLAN 100 is not specified in the allowed VLAN range forge-0/0/0(which is 101-120),nor is it specified underge-0/0/1. Therefore, it will be dropped.References:

• Understanding VLAN Tagging, Juniper TechLibrary
• Configuring VLANs for EX Series Switches, Juniper TechLibrary