Install and Troubshoot Routers

Question 1

Edge Router

Answer 1

• Placed at network perimeters

- Have External and internal interfaces

Question 2

Internal Router

Answer 2

• Has no public interfaces

- Positions to implement network topology

Question 3

Layer 3 Switch

Answer 3

• Switch optimized for routing between VLANs
• Uses static and dynamic routing to identify which VLAN an IP address should be forwarded to.
• Can keep mapping table of IP and MAC addresses
• Do not typically have WAN interfaces and to used for edge routing

Question 4

show route, show ip route, show ipv6 route

Answer 4

• Outputs active routing table

Question 5

route command

Answer 5

• Used to view and modify routing table of end system Windows and Linux hosts.
• Add roue:
  “route [-f -p] add destinationIP mask netmask gatewayip metric metricvalue(cost of route) if interface
• nonpersistent by default, -p switch makes it permenant

Question 6

traceroute

Answer 6

• Tool that allows testing of path between nodes
• Linux and router OSs
• Shows number of hops, address of ingress interface of router and time taken to respond.

Question 7

routing loop

Answer 7

• When two routers use one another as path to a network

- Symptom is generation of ICMP Time exceeded messages

Question 8

Subinterface

Answer 8

Virtual interface

• VLAN traffic must be routed
• All VLAN-VLAN traffic goes through router on trunk port/single interface
• Each subinterface has VLAN ID
• Routes between each VLAN’s sub interface

Question 9

tracert

Answer 9

• Windows system command to test whole path between nodes
• -d switch suppresses name resolution
• -h specify max number of hops
• -w specify timeout in ms

Question 10

show ip w.x.y.z

Answer 10

• Checks presence of a route to specific IP network

Question 11

Maximum hop Count

Answer 11

• Method to prevent routing loop
• Network is deemed unreachable if hop count exceeds certain value
• Poison route is one advertised over hop count limit

Question 12

Holddown timer

Answer 12

• If a node declares a network unreachable, its neighbors start hold-down time
• Any updates about that route are discarded for duration
• Ensures that all nodes have converged information about unreachable network

Question 13

Split Horizon

Answer 13

• ## Prevents routing update from being copied back to the source