Objectives
The simulator ticks each one as soon as the network meets it.
SW1 (Cisco): VLANs 10 and 20, PC1 in VLAN 10, PC2 in VLAN 20, trunk on G0/0.
CORE (Huawei): VLANs 10/20, trunk on G0/0/0, Vlanif10 192.168.10.1/24 and Vlanif20 192.168.20.1/24.
CORE: DHCP pools for both VLANs (dns 8.8.8.8, dhcp select global on the VLANIFs); PCs lease addresses.
CORE G0/0/1 as a routed port 10.0.0.1/30; OSPF area 0 between CORE and EDGE.
EDGE (Cisco): default route to the ISP, advertised into OSPF; PAT for 192.168.0.0/16 out G0/1.
PC1 pings 8.8.8.8 and PC2.
Before you start
Huawei switch ports become routed with undo portswitch. The Cisco trunk allows VLANs 10,20; the Huawei trunk uses port trunk allow-pass vlan 10 20. default-information originate on EDGE gives CORE its default route.
Concept
802.1Q trunks: VLAN tags on the wire
A trunk carries many VLANs over one link. To keep them apart, the sending switch inserts a 4-byte 802.1Q tag into each frame saying which VLAN it belongs to; the receiving switch reads the tag and removes it before delivering the frame to an access port.
Concept
Inter-VLAN routing on a Layer 3 switch (SVI / VLANIF)
A Layer 3 switch can route between its own VLANs. Each VLAN gets a virtual interface (Cisco SVI interface vlan 10, Huawei interface Vlanif 10) holding that VLAN’s gateway address, so no external router or trunk is needed.
Concept
DHCP and DHCP relay
DHCP hands out IP address, mask, gateway and DNS server automatically. A new host has no address, so it broadcasts — and broadcasts stop at routers. A relay agent on the host’s router forwards the request to a server on another subnet.
Concept
NAT overload (PAT / Easy IP)
Private addresses are not routed on the Internet. Port address translation lets many inside hosts share one public address: the router rewrites the source address (and if needed the source port) of outgoing packets and keeps a table to reverse it for replies.
