Networking Fundamentals

A host in VLAN 10 can ping a host in VLAN 20 without a default gateway configured. What feature is likely enabled on the router that interconnects the VLANs?

Which field in an Ethernet frame is used by a switch to learn which source MAC address belongs to which port?

You are troubleshooting a network connectivity issue at a medium-sized company that uses Juniper EX4300 switches. Users in VLAN 100 (10.10.100.0/24) report that they cannot access a server in VLAN 200 (10.10.200.0/24). The switch has IRB interfaces configured for both VLANs and is acting as the default gateway. The IRB interfaces are up and have correct IP addresses. The server and users have correct IP configurations. 'show arp' on the switch shows incomplete entries for some hosts in VLAN 100. 'show ethernet-switching table' shows MAC addresses for users are present on the correct access ports. However, pings from the switch to a user in VLAN 100 fail. What is the most likely issue?

You are troubleshooting an OSPF adjacency issue between two Juniper MX series routers, R1 and R2, both running Junos 18.2. They are directly connected via a Gigabit Ethernet link. R1's interface ge-0/0/0 is configured with IP 192.168.1.1/24, and R2's ge-0/0/0 is configured with IP 192.168.1.2/24. Both interfaces are in OSPF area 0.0.0.0. The physical connectivity is confirmed up, and both interfaces are administratively enabled. You have checked that the hello and dead intervals match (hello 10, dead 40), the area IDs are identical, and the subnet masks are /24. No firewall filters are blocking OSPF. The OSPF configuration on R1 includes 'authentication-type md5' and 'authentication-key juniper123' under the interface. On R2, the configuration also includes 'authentication-type md5' but the key is 'juniper321'. Both routers have loopback addresses as router IDs: 1.1.1.1 for R1 and 2.2.2.2 for R2. No explicit OSPF network type is set, so the default is broadcast. Despite these configurations, the OSPF adjacency state on both routers remains in INIT. What is the most likely cause of this issue?

Refer to the exhibit. The OSPF neighbor adjacency repeatedly goes up and down on R1. What is a likely cause?

A network administrator is configuring a new subnet for servers that must not communicate with each other directly but must be able to reach a default gateway. Which type of route should be configured on the servers?

A network engineer is troubleshooting OSPF adjacencies between two Juniper routers. The routers are directly connected and have matching OSPF configurations except for the router IDs. Router A has router-id 10.0.0.1, Router B has router-id 10.0.0.2. The adjacency remains in the EXSTART state. What is the most likely cause?

A network engineer is troubleshooting connectivity between two directly connected Juniper routers. The interface on Router A shows 'up' but no packets are being received from Router B. Which command should the engineer use on Router A to check if the interface is expecting to receive a specific encapsulation type?

Refer to the exhibit. A frame with destination MAC 00:0c:29:2a:3b:4d arrives on interface ge-0/0/0. What action will the switch take?

A network engineer sees an unknown unicast flood on a Juniper EX switch. Which mechanism is most effective at reducing such floods?

A network administrator notices that traffic between two VLANs is not reaching its destination. The switch has an IRB interface configured with an IP address in each VLAN's subnet. What is the most likely missing configuration?

An engineer is troubleshooting a network issue where hosts on the same VLAN cannot communicate with each other. Which configuration element is most likely missing?

An engineer enables Spanning Tree PortFast on a switch port connected to a host. Later, another switch is connected to that same port, causing a loop. What feature could have prevented this?

A switch receives a unicast frame with a destination MAC address that is present in its MAC address table. How does the switch process the frame?

A router receives a packet with destination IP 10.1.1.100. The routing table contains two entries: a static route to 10.1.1.0/24 via 192.168.1.1, and an OSPF route to 10.1.1.0/25 via 192.168.2.1. Which route will the router use?

A host needs to verify that its assigned IP address is not already in use on the network. Which type of packet does the host send?

Arrange the steps to configure an IPsec VPN on a Junos SRX in the correct order.

You are responsible for a Juniper MX router that connects two customer sites over a Layer 3 VPN. The router is configured with BGP for VPN routes and uses MPLS to forward traffic. Recently, the customer reported that traffic from Site A (10.0.1.0/24) to Site B (10.0.2.0/24) is intermittently failing. You check the routing table on the router and see that both routes are present with valid next-hops. However, when you ping from the router's loopback to the remote site's loopback, the ping succeeds. MPLS labels are being assigned and the LSP is up. You also notice that when the failure occurs, the router's BGP session to the remote PE is still established. The failure seems random and lasts a few seconds before recovering. Which troubleshooting step is most likely to identify the root cause?

A company is deploying an EVPN-VXLAN fabric with Juniper QFX switches. To provide inter-subnet routing, which interface type must be configured?

A Juniper router is configured with two static routes to the same destination network, both with the same preference. One route has a metric of 5, the other a metric of 10. Which route will be installed in the routing table?

You are a network engineer for a large enterprise deploying a new data center using a spine-and-leaf architecture with Juniper QFX5100 switches. The underlay network uses OSPF for loopback reachability, and the overlay uses EBGP for EVPN. The leaf switches are configured as VTEPs (Virtual Tunnel Endpoints). One of the leaf switches, leaf-03, cannot establish OSPF adjacency with its spine switch, spine-01. The interfaces are up/up and the IP addresses are correctly configured. 'show ospf neighbor' on leaf-03 returns nothing. 'show ospf interface' shows the interface is in state DOWN. Both switches are configured with the same OSPF area (0.0.0.0) and the same hello interval (10 seconds). The MTU on both sides is 1500. Authentication is not configured. The spine switch has multiple OSPF neighbors from other leaves. The network is in production and other leaf switches are working fine. What is the most likely cause of the problem?

Refer to the exhibit. A host connected to ge-0/0/1 cannot reach a host connected to ge-0/0/2 even though both are in VLAN10. What is the most likely cause?