Learning paths

0 / 8 marked in this browserMark all

1. VLANs — Splits one physical switched network into several independent broadcast domains, and carries them over a shared link with a four-octet tag.
2. STP — Keeps a switched network free of loops by disabling just enough ports to leave one active path between any two bridges.
3. RSTP — Replaces spanning tree’s two timers with an explicit handshake, and names the backup path in advance so failover does not wait for information to expire.
4. MSTP — Maps many VLANs onto a handful of spanning trees, and decides who shares a topology by hashing the mapping rather than by trusting the configuration to match.
5. PVST+ — One spanning-tree instance per VLAN — Cisco’s way to load-share uplinks where IEEE STP/RSTP would keep a single tree.
6. LACP — A standard handshake that binds parallel links into one logical port — and refuses to forward on a member the far end has not agreed to.
7. vPC — Two Nexus peers present one LACP system downstream; peer-keepalive is the split-brain detector when the peer-link fails.
8. LLDP — A standard TLV advertisement of chassis, port, and TTL — vendor-neutral neighbour discovery.

0 / 6 marked in this browserMark all

1. OSPFv2 — Each router floods a description of its links, then independently computes the same shortest-path tree — so the forwarding tables agree without exchanging routes.
2. OSPFv3 — The same neighbor machine and SPF as OSPFv2, with addressing stripped out of the LSA so Instance IDs can map separate address families onto the same control plane.
3. IS-IS — A CLNS link-state protocol that carries IP as TLVs: areas are levels, the LAN elects a DIS that preempts, and the metric width is a configuration, not a constant.
4. EIGRP — A distance-vector protocol that keeps a proven loop-free backup ready, so most failures are a switch rather than a recomputation — and asks the network only when it has none.
5. RIPv2 — The clearest distance-vector lesson: hop count to 15, infinity at 16, split horizon, and poison reverse.
6. BGP — A TCP session that exchanges path attributes, then picks one path with a total-order waterfall — not a shortest-path flood.

0 / 4 marked in this browserMark all

1. VXLAN — Carries an Ethernet frame inside UDP so a layer-two segment can span a routed fabric, identified by a 24-bit VNI rather than a 12-bit VLAN tag.
2. EVPN — Advertises MAC addresses in BGP instead of discovering them by flooding, which is what makes all-active multihoming and predictable mobility possible.
3. BGP — A TCP session that exchanges path attributes, then picks one path with a total-order waterfall — not a shortest-path flood.
4. OSPFv2 — Each router floods a description of its links, then independently computes the same shortest-path tree — so the forwarding tables agree without exchanging routes.

0 / 5 marked in this browserMark all

1. LDP — UDP discovery on 646, then a TCP session that maps FECs to labels so the IGP’s path can be label-switched.
2. SR-MPLS — A prefix SID is a node label from the SRGB; an adjacency SID is one hop. TI-LFA is a repair stack — not RSVP-TE.
3. L3VPN — VPN-IPv4 is an RD plus a prefix; import is a Route Target. They are unrelated — and the data plane needs a transport label as well as a VPN label.
4. BGP — A TCP session that exchanges path attributes, then picks one path with a total-order waterfall — not a shortest-path flood.
5. IS-IS — A CLNS link-state protocol that carries IP as TLVs: areas are levels, the LAN elects a DIS that preempts, and the metric width is a configuration, not a constant.

0 / 3 marked in this browserMark all

1. IGMP — Hosts report which multicast groups — and, in version 3, which sources — they want; snooping turns those reports into switch forwarding state.
2. PIM-SM — Builds multicast trees only where receivers ask for them, meeting sources and receivers at a rendezvous point and then getting out of the way.
3. Bidir-PIM — Many-to-many multicast on a shared tree only — no Register, no (S,G), no SPT switchover; the DF on each link is what keeps it loop-free.