Fast switching First packet to a specific destination IP is process switched. With the first packet the router adds an entry in the fast switch cache, also called route cache. The cache contains the destination IP, data link header information
IP services – Notes
ARP Address Resolution Protocol, used to discovery layer two address when IP address is already known. Uses protocol 0x0806 compared to Ethernet which uses 0x0800. At layer two an ARP request is a broadcast since the MAC address of the
Spanning tree – notes
Electing the root Only one switch can be the root bridge. From the start all switches announce themselves as the root, when a switch hears of a superior BPDU it stops announcing itself as the root and instead forwards the
VLAN – Notes
Private VLANs Commonly used in SP networks to put users in common subnet but no direct forwarding of packets between customers in same VLAN. Enforce security by forcing traffic to go through router instead of switched locally. There are three
Ethernet – notes
RJ 45 pinouts 10-BASE-T and 100BASE-TX uses pairs two and three, gigabit Ethernet uses all four pairs. Pinout for straight cable: 1-1;2-2;3-3;6-6 Pinout for crossover cable: 1-3;2-6;3-1;6-2 A standard PC transmits on pair one and two and receives on three
Quality of Service – notes
Hardware queue Packets can be sent trough hardware queue without interrupting CPU Always uses FIFO logic Cannot be affected by IOS queuing tools Class Based Weighted Fair Queing Every class (queue) gets a defined percentage/amount of bandwidth If a class
IPv6 – notes
Addresses are 128 bits long Separated with colons every 16 bits Address separated in prefix and interface id, most common is /64 Leading zeroes can be omitted from address and double colon may be used to represent Successive zeroes, may
MPLS – notes
First defined in RFC 2547 Originally called tag switching and was Cisco proprietary MPLS is the open standard Operates at layer 2.5 between switching and routing Terms used in MPLS: LER = Label Edge Router – MPLS capable, placed at
Border Gateway Protocol (BGP) – notes
Uses TCP as transport, port 179 Path vector protocol Checks before becoming a neighbor The TCP connection request must come from an IP associated with a neighbor command The AS number must match that in the neighbore statement The routers
Enhanced Interior Gateway Protocol (EIGRP) – notes
Cisco proprietary Uses IP protocol 88 as transport Support for MD5 authentication (no clear text) Sends updates to 224.0.0.10 Distance vector but has some link state like features Timers Uses a hello and a hold timer. Neighbors discovered via hello