Routing Protocols

Chapters 9 & 10

NetTech Solutions

What you will learn

• This chapter focuses on dynamic routing protocols.– Distant Vector– OSPF

For a Router to Route Data

• A router must know at least– Destination address– Neighbor routers from which it can learn

about remote networks– Possible routes to all remote networks– The best route to each remote network– How to maintain and verify routing

information

A Simple Routing Example

Autonomous System (AS)

Interior gateway protocols (IGPs)Exterior gateway protocols (EGPs)Border Gateway Protocol (BGP)

Routing Flow Tree

Administrative Distances

• The Administrative Distance (AD) is used to rate the trustworthiness of routing information received on one router from its neighboring router. (0 to 255)

Administrative Distance

Classes of Routing Protocols

• Distance Vector– Rip, Rip2, and IGRP

• Link State– OSPF, and IS-IS

• Hybrid– EIGRP

Distance Vector Routing

• Routing tables are then updated with all route information gathered from neighbor routers:

Converged routing tables

• Three important things:– The remote network number– The interface that the router will use to send

packets to reach that particular network– The hop count, or metric, to the network

RIPv1 vs. RIPv2

VLSM and Discontiguous Networks

Classless network design

Discontigous Networks

• Discontiguous networks just won’t work with RIPv1 or IGRP at all.

EIGRP

• EIGRP is a classless, enhanced distance-vector protocol that gives us a real edge over another Cisco proprietary protocol, IGRP. That’s basically why it’s called Enhanced IGRP.

• IGRP is an older routing protocol and no longer supported by Cisco.

EIGRP Supports

• Support for IP and IPv6• Considered classless• Support for VLSM / Classless Inter-Domain Routing

(CIDR)• Support for summaries and discontiguous networks• Efficient neighbor discovery• Communication via Reliable Transport Protocol (RTP)• Best path selection via Diffusing Update Algorithm

(DUAL)

EIGRP

• Creates and Maintains additional tables

Keeps state information about adjacent neighbors

Populated by the neighbor table, and the best path to each remote network is found by running DUAL.

A feasible successor (best)A successor route (think successful!)

Border Gateway Protocol (BGP)

Link-State Routing Protocols

• Open Shortest Path First (OSPF)– Consists of areas and autonomous

systems– Minimizes routing update traffic– Allows scalability– Supports VLSM/CIDR– Has unlimited hop count– Allows multi-vendor deployment (open

standard)

OSPF – RIP Comparison

• Characteristic OSPF RIPv2 RIPv1• Type of protocol Link state Distance vector Distance

vector• Classless support Yes Yes No• VLSM support Yes Yes No• Auto-summarization No Yes Yes• Manual summarization Yes No No• Discontiguous support Yes Yes No• Route propagation Multicast on change Periodic multicast Periodic

broadcast

• Path metric Bandwidth Hops Hops• Hop-count limit None 15 15• Convergence Fast Slow Slow• Peer authentication Yes Yes No• Hierarchical network Yes (using areas) No (flat only) No (flat only)• Updates Event triggered Route table updates Route table

updates

• Route computation Dijkstra Bellman-Ford Bellman-Ford

OSPF design example

Intermediate System to Intermediate System (IS-IS)

• The difference between IS-IS and OSPF is that IS-IS only uses Connectionless Network Service (CLNS) to provide connectionless delivery of data packets between routers. OSPF uses IP to communicate between routers instead.

IS-IS Network Terminology

IPv6 Routing Protocols

• Broadcast is eliminated• RIPng

– Still uses multicast to send its updates, too; but in IPv6, it uses FF02::9 for the transport address.

• EIGRPv6– In IPv4 it was 224.0.0.10; in IPv6, it’s FF02::A (A = 10 in

hexadecimal notation).

• OSPFv3– OSPFv3 still uses multicast traffic to send its updates and

acknowledgements, with the addresses FF02::5 for OSPF routers and FF02::6 for OSPF-designated routers.

VLANs

Chapter 11

NetTech Solutions

Switching and Virtual LANs (VLANs)

• PoE• Spanning tree• VLAN• Trunking• Port mirroring• Port authentication

Examples of Switched Networks

Bridging vs. LAN Switching

• Bridges are software based, whereas switches are hardware based because they use ASIC chips to help make filtering decisions.

• A switch can be viewed as a multiport bridge.• There can be only one spanning-tree instance per bridge,

whereas switches can have many. (I’m going to tell you all about spanning trees in a bit.)

• Switches have a higher number of ports than most bridges.

• Both bridges and switches forward Layer 2 broadcasts.• Bridges and switches learn MAC addresses by examining

the source address of each frame received.• Both bridges and switches make forwarding decisions

based on Layer 2 addresses.

Switching Services

• Unlike bridges, which use software to create and manage a filter table, switches use application-specific integrated circuits (ASICs) to accomplish this.

• Layer 2 switches and bridges are faster than routers because they don’t take up time looking at the Network-layer header information.

• Switches create private, dedicated collision domains and provide independent bandwidth on each port, unlike hubs

Three Switch Functions at Layer 2

• Address learning• Forward/filter decisions• Loop avoidance

Address learning

Forward/Filter Decisions

Output of a show MAC address-table command

Switch#sh mac address-table

Vlan Mac Address Type Ports

-------- --------------------- -------- -----

1 0005.dccb.d74b DYNAMIC Fa0/1

1 000a.f467.9e80 DYNAMIC Fa0/3

1 000a.f467.9e8b DYNAMIC Fa0/4

1 000a.f467.9e8c DYNAMIC Fa0/3

1 0010.7b7f.c2b0 DYNAMIC Fa0/3

1 0030.80dc.460b DYNAMIC Fa0/3

1 0030.9492.a5dd DYNAMIC Fa0/1

1 00d0.58ad.05f4 DYNAMIC Fa0/1

Loop Avoidance

• Broadcast storm

Spanning Tree Protocol (STP)

• DEC created the original version of Spanning Tree Protocol (STP).

• IEEE later created its own version of STP called 802.1D.

• By default, most switches run the IEEE 802.1D version of STP.

• A new industry standard called 802.1w.• STP’s main task is to stop network loops from

occurring on your Layer 2 network (bridges or switches).

A switched network with switching loops

Spanning-Tree Port States

• Blocking• Listening• Learning• Forwarding• Disabled

STP Convergence

• Convergence is what happens when all the ports on bridges and switches have transitioned to either forwarding or blocking modes.

Virtual LANs (VLANs)

• Here with a hub every broadcast packet transmitted is seen by every device on the network regardless of whether the device needs to receive that data or not.

Virtual LANs (VLANs)

• With a switch the frame is only forwarded out of the port where Host D is located.

Physical LANs connected with routers

Switches removing the physical boundary

VLAN Memberships

• Static VLANs– VLANs are created by a system

administrator who proceeds to assign switch ports to each VLAN.

• Dynamic VLANs– Using intelligent management software, you

can base VLAN assignments on hardware (MAC) addresses, protocols, or even applications that work to create dynamic VLANs.

Identifying VLANs

• There are two different types of links in a switched environment: access ports and trunk ports.– Access Ports: An access port belongs to and

carries the traffic of only one VLAN.– Trunk Ports: trunk ports can carry multiple

VLANs at a time.– A trunk link is a 100- or 1000-Mbps point-to-

point link between two switches, between a switch and router, or even between a switch and server, and it carries the traffic of multiple VLANs—from 1 to 4,094 at a time.

Access and trunk links in a switched network

Inter-Switch Link (ISL)

• Inter-Switch Link (ISL) is a way of explicitly tagging VLAN information onto an Ethernet frame.

• By running ISL, you can interconnect multiple switches and still maintain VLAN information as traffic travels between switches on trunk links.

Switching and Network Security

• Port Security/Authentication– Using 802.1x authentication on your

switch

Two Additional Advanced Features of Switches

• Power over Ethernet (PoE)• Port Mirroring/Spanning

– Port mirroring, also called Switch Port Analyzer (SPAN), allows you to sniff traffic on a network when using a switch.