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Ruankao Network Engineer (Intermediate) study materials
Ruankao Network Engineer (Intermediate) study resources

Ruankao Network Engineer (Intermediate): Network Interconnection and Device Configuration

Ruankao Network Engineer (Intermediate) · Work through your exam, one topic at a time.

All guide sections

Network Interconnection and Device Configuration

This domain is operational: interface setup, routing configuration, ACLs, NAT, firewall policy and wireless controller integration. Questions appear as command snippets where you must spot the missing or wrong line.

Routers and Layer 3 configuration

  • Bring an interface up: assign the address and mask, then no shutdown (Cisco) or undo shutdown (Huawei).
  • Static route: ip route 0.0.0.0 0.0.0.0 203.0.113.1 - the default route. Floating static routes use a higher administrative distance as a backup.
  • Dynamic routing needs matching network statements or interface-level enablement, plus consistent area or AS numbers.
  • NAT: define inside/outside interfaces, then a source list and a pool or overload statement for PAT.

Switch configuration and inter-VLAN routing

  • Create VLANs, assign access ports (switchport mode access, switchport access vlan 10), and configure trunks (switchport mode trunk, allowed VLAN list).
  • Single-arm routing: interface g0/0.10 with encapsulation dot1q 10 and an IP address acting as the gateway for VLAN 10.
  • On a Layer 3 switch, use interface vlan 10 with ip address and enable ip routing.

Firewalls and wireless

  • Firewalls work with zones (inside/trust, outside/untrust, DMZ) and ordered policies; the first match wins, and an implicit deny usually terminates the list. Stateful inspection permits return traffic automatically.
  • A wireless controller manages thin APs over CAPWAP (UDP 5246 control, 5247 data). The WLAN profile binds an SSID to a VLAN and security policy; APs are typically powered by PoE.

Troubleshooting sequence

Work bottom-up: link light and show interface counters (errors, duplex mismatch), then ARP and addressing, then show ip route, then ACL and NAT translation tables, then application ports. Use ping, traceroute, and debug/display commands cautiously on production devices.

Worked example

Users in VLAN 20 cannot reach VLAN 30 on the same switch, though both VLANs work internally. The trunk between the switch and router is up, but show run interface g0/0.20 shows encapsulation dot1q 20 with no IP address. Without a gateway address, hosts have no next hop; adding ip address 192.168.20.1 255.255.255.0 on the sub-interface restores routing.

Traps that cost marks

  • Leaving an interface administratively down after configuration.
  • Using a subnet mask where an ACL requires a wildcard (inverse) mask - for /24 the wildcard is 0.0.0.255.
  • Misordering ACL entries so a permit-any line shadows later denies.
  • Forgetting that a trunk native VLAN must match at both ends.