2.1 - Routing technologies
Network+ N10-009 objective 2.1 covers how traffic is routed between networks. A router forwards traffic between different IP networks using its routing table. BGP is the routing protocol of the internet: an eBGP session is established between two different autonomous systems, while an iBGP session peers routers within the same autonomous system. When hosts on VLAN 10 and VLAN 20 need to communicate, inter-VLAN routing - via a router or a Layer 3 switch - provides it, since VLANs are separate broadcast domains. You should also know static versus dynamic routing, OSPF and EIGRP, administrative distance, metrics, and default routes. Expect scenario questions that describe traffic crossing networks or autonomous systems, or VLANs that must talk, and ask which routing technology - a router, eBGP, iBGP or inter-VLAN routing - is the correct answer.
Forward between IP networks = router. BGP between different autonomous systems = eBGP; within the same AS = iBGP. VLAN 10 to VLAN 20 = inter-VLAN routing (router or L3 switch).
Practice questions
1. Which standard tags frames to carry multiple VLANs over a trunk link?
- 802.1X
- 802.1Q (correct answer)
- 802.3af
- 802.11ac
802.1Q inserts a VLAN tag into Ethernet frames so a trunk can carry many VLANs. 802.1X is port access control, 802.3af is PoE, 802.11ac is Wi-Fi 5.
2. Which device forwards traffic between different IP networks?
- Hub
- Switch
- Repeater
- Router (correct answer)
A router operates at Layer 3 and forwards packets between networks using IP and a routing table. Switches forward within a LAN (MAC); hubs/repeaters just repeat signals.
3. Which routing protocol is a link-state interior gateway protocol?
- RIP
- OSPF (correct answer)
- BGP
- EIGRP
OSPF is a link-state IGP that builds a full topology and picks paths by cost. RIP is distance-vector (hop count), BGP is the exterior path-vector protocol of the Internet, EIGRP is Cisco advanced distance-vector.
4. Which redundancy protocol provides a virtual gateway IP shared by two routers?
- OSPF
- VRRP (correct answer)
- LACP
- STP
VRRP (a FHRP) lets two routers share a virtual IP so hosts keep one default gateway even if the active router fails. OSPF routes, LACP bonds links, STP blocks loops.
5. A default route in a routing table is written as:
- 255.255.255.255/32
- 0.0.0.0/0 (correct answer)
- 127.0.0.0/8
- 169.254.0.0/16
0.0.0.0/0 matches any destination and is the default route (gateway of last resort). 127.0.0.0/8 is loopback, 169.254 is APIPA.
6. When two routing protocols offer a route, which value decides which one is installed?
- Administrative distance (correct answer)
- The lowest hop count
- The source MAC address
- The interface MTU size
Administrative distance ranks the trustworthiness of route sources; the lowest AD is preferred. Metric (like hop count) only breaks ties within one protocol.