CIS 185 Advanced Routing ProtocolsEIGRP Part 2 pot

EIGRP over Frame Relay: Physical Interface with Dynamic Mapping  Inverse ARP is on by default  Automatically maps the IP address of the devices at the other end of the PVCs to the loc

CIS 185 Advanced Routing Protocols

EIGRP Part 2

Rick GrazianiCabrillo Collegegraziani@cabrillo.eduFall 2012

EIGRP Part 2

 EIGRP over Frame Relay

 EIGRP over MPLS

 EIGRP Load Balancing

 EIGRP Bandwidth across WAN Links

 Authentication

 EIGRP Scalability in Large Networks

Materials

 Book:

 Implementing Cisco IP Routing

(ROUTE) Foundation Learning

Guide: Foundation learning for the

Configuring and Verifying

EIGRP in an Enterprise WAN

Physical Frame-RelayMultipoint and point-to-point Frame-Relay subinterfacesMultiprotocol Label Switching (MPLS) virtual private networks (VPNs)

Ethernet over Multiprotocol Label Switching (EoMPLS)

4

Frame Relay Basics

 Frame Relay Basics

 A switched WAN technology

 Virtual circuits (VCs) are created by a Service Provider (SP)

 Multiple logical VCs to be multiplexed over a single physical interface

 Typically PVCs identified by a locally significant data link connection

identifier (DLCI)

 For IP connectivity: A mapping between IP addresses and DLCIs must

be defined, either dynamically or statically 5

Frame Relay Basics

 By default, a Frame Relay network is an NBMA network

 Like multiaccess networks (Ethernet LANs) All routers are on the same

subnet

 But broadcast (and multicast) packets CANNOT be sent just once as they

are in a broadcast environment such as Ethernet

 Cisco IOS implements pseudo-broadcasting

 Router creates a copy of the broadcast or multicast packet for each

neighbor reachable through the WAN media (over the PVC)

 Sends the copy of the broadcast or multicast packet over the appropriate

EIGRP over Frame Relay:

Physical Interface with Dynamic Mapping

 Inverse ARP is on by default

 Automatically maps the IP address of the devices at the other end of the

PVCs to the local DLCI number

 Split horizon is disabled by default on Frame Relay physical interfaces

 Routes from Router R2 can be sent to Router R3, and vise-versa

 Note: Inverse ARP does not provide dynamic mapping for the communication

between routers R2 to R3 because they are not connected with a PVC; this

must be configured (mapped) manually

7

DLCI 100

DLCI 130

EIGRP over Frame Relay:

Physical Interface with Dynamic Mapping

 R1 forms the adjacency with router R2 and R3 over the serial0/0 physical

interface

 R3 (and R2) forms an adjacency with router R1

 No EIGRP relationship exists between routers R2 and R3

8

EIGRP over Frame Relay:

Physical Interface with Static Mapping

 Using static mapping disables Inverse ARP

 No changes to the basic EIGRP configuration

 Manual IP-to-DLCI mapping commands on the serial 0/0 interface are

necessary on all three routers

 Again, because split horizon is disabled by default on Frame Relay physical

interfaces, routes from R2 can be sent to R3, and vise-versa

 Note: R1 includes a Frame Relay map to its own IP address so it can ping its

R1

interface Serial 0/0 encapsulation frame-relay

ip address 192.168.1.103 255.255.255.0 frame-relay map ip 192.168.1.101 130 broadcast router eigrp 110

network 192.168.1.0

R3

EIGRP over Frame Relay:

Physical Interface with Static Mapping

 The adjacencies formed on R1 using static mapping are the same as those

formed using dynamic mapping

 R2 and R3 also form an adjacency with router R1

 R2 and R3 can also form an EIGRP adjacency to each other if the IP-to-DLCI mapping for that connectivity is provided

 Output shows that R3 has two neighbors (router R1 and R2), indicating that

this mapping was provided on R3 (but not required between R2 and R3) 10

interface Serial 0/0 encapsulation frame-relay

ip address 192.168.1.103 255.255.255.0 frame-relay map ip 192.168.1.101 130 broadcast frame-relay map ip 192.168.1.102 130 broadcast router eigrp 110

network 192.168.1.0

R3

EIGRP over Frame

Relay:

Multipoint

Subinterfaces

 Separating a physical interface into multipoint subinterfaces allows

each subinterface to be on a separate network.

 Multipoint subinterfaces are configured with the command:

interface serial number.subinterface-number multipoint

11

DLCI 100 DLCI 130 DLCI 103

Same Subnet

EIGRP over Frame Relay:

Multipoint Subinterfaces

 IP address-to-DLCI mapping on multipoint subinterfaces is done by either:

 Specifying the local DLCI value (frame-relay interface-dlci dlci)

and relying on Inverse ARP

 Using manual IP address-to-DLCI mapping

 The physical interface serial 0/0 is configured for Frame Relay encapsulation and does not have an IP address assigned to it

 Note: The spoke router does not have a multipoint-subinterface 12

frame-relay map ip 192.168.1.102 102 broadcast

frame-relay map ip 192.168.1.103 103 broadcast

router eigrp 110

network 192.168.1.0

network 172.16.1.0 0.0.0.255

R3 interface Serial 0/0

no ip address encapsulation frame-relay interface serial 0/0/0.1 multipoint

ip address 192.168.1.103 255.255.255.0 frame-relay map ip 192.168.1.101 130 broadcast router eigrp 110

network 192.168.1.0

EIGRP over Frame Relay:

Multipoint Subinterfaces

 Split horizon is enabled by default on Frame Relay multipoint interfaces

 R2 and R3 need to provide connectivity between their connected networks so…

 EIGRP split horizon is disabled on the multipoint subinterface of router R1

with the no ip split-horizon eigrp as-number command

frame-relay map ip 192.168.1.102 102 broadcast

frame-relay map ip 192.168.1.103 103 broadcast

router eigrp 110

network 192.168.1.0

network 172.16.1.0 0.0.0.255

R3 interface Serial 0/0

no ip address encapsulation frame-relay interface serial 0/0/0.1 multipoint

ip address 192.168.1.103 255.255.255.0 frame-relay map ip 192.168.1.101 130 broadcast router eigrp 110

network 192.168.1.0

EIGRP over Frame Relay:

Multipoint Subinterfaces

 Verify with show ip eigrp neighbors

 R1 forms an adjacency with routers R2 and R3 over the serial0/0.1 multipoint subinterface

 R2 and R3 form the adjacency with R1

 Note: R2 and R3 could form an adjacency between each other if the IP

address-to-DLCI mapping for that connectivity is provided (not required) 14

EIGRP over Frame Relay:

Unicast Neighbors

 Not all Frame Relay service providers support multicasts/broadcasts so routing

information must be sent as unicasts.

neighbor {ip-address | ipv6-address} interface-type interface-number

 Defines a neighboring router to exchange EIGRP routing information.

 Instead of using multicast packets, EIGRP exchanges routing information with the

R2R1

EIGRP over Frame Relay:

Unicast Neighbors

 EIGRP does not process any multicast packets coming inbound on that interface

 EIGRP stops sending multicast packets on that interface

16

R2R1

EIGRP over Frame Relay:

Unicast Neighbors

 R1 is configured with a neighbor command for R2

 R1 will therefore not accept multicast packets on Serial 0/0.1 anymore

 R2 must also be configured with a neighbor command for R1 to establish an

adjacency

 R1 and R3 are not configured with a neighbor command for each other.

 Therefore, R1 and R3 will not form an adjacency 17

R2R1

unicast multicast

EIGRP over Frame Relay:

Unicast Neighbors

 Because R3 is not using the neighbor command it tries to communicate

with multicast packets on its Serial 0/0/.1

 However, neighborship is not established because neither R1 nor Router R2 is accepting multicast packets.

18

R1

R3 interface Serial 0/0

no ip address encapsulation frame-relay interface serial 0/0/0.1 multipoint

ip address 192.168.1.103 255.255.255.0 frame-relay map ip 192.168.1.101 130 broadcast router eigrp 110

network 192.168.1.0

EIGRP over Frame

Relay:

Point-to-Point

Subinterfaces

 Point-to-point subinterfaces are logical interfaces:

 Emulates a leased line network

 Provide a routing equivalent to point-to-point physical interfaces

 As with physical point-to-point interfaces, each interface requires its own

subnet

 Frame Relay point-to point is applicable to hub and spoke topologies

19

DLCI 100 DLCI 130 DLCI 103

Same Subnet

EIGRP over Frame Relay:

EIGRP over Frame Relay:

Point-to-Point Subinterfaces

 Point-to-point subinterfaces are created with the command:

interface serial number.subinterface-number point-to-point

 IP address-to-DLCI mapping on point-to-point subinterfaces with:

frame-relay interface-dlci dlci

 R1 has two point-to-point subinterfaces, one for each subnet and DLCI

EIGRP over MPLS

 MPLS (Multiprotocol Label Switching) is an IETF standard.

 Combines the:

 Advantages of Layer 3 routing

 Benefits of Layer 2 switching

 Short fixed-length labels are assigned to each packet at the edge of the MPLS network

 Allows for scalable VPNs, end-to-end QoS, and other IP services that allow

efficient utilization of existing networks with simpler configuration,

management, and quicker fault correction

22

What is the problem MPLS is trying to solve?

 Layer 3 End-to-end circuits

 Advantages

 IP routing provides dynamic, automatic path setup

 Provides best path and backup paths

 Provides QoS

 Disadvantages

 Latency in hop-by-hop Layer 3 lookup

 Latency in routing – switching – packet forwarding process

What is the problem MPLS is trying to solve?

 Layer 2 End-to-end circuits (ATM, Frame Relay)

MPLS WAN Connectivity

 MPLS extends Layer 2 or Layer 3 natively between sites

 The MPLS network although owned by a service provider but is an extension of the enterprise network

 MPLS network is like a single router or switch with multiple interfaces

 MPLS philosophy is that the Layer 3 header contains significantly more

information than is necessary to forward the packet

 MPLS domain – A contiguous set of nodes performing MPLS routing and

forwarding

 These are typically in one routing or administrative domain

 Label Switching Router (LSR) – An MPLS node that is capable of

forwarding labeled packets

 Label – A short, fixed-length, physically contiguous identifier used to identify

a group of networks sharing a common destination, usually of local

MPLS Operation

 A label identifies a flow of packets (for example, voice traffic between two

nodes), also called a Forwarding Equivalence Class (FEC)

 Grouping of packets which can be used for QoS requirements

 Packets belonging to the same FEC receive the same treatment in the

network

 Determined by various parameters including:

 source or destination IP address

 port numbers

 IP protocol

 IP precedence

28

MPLS Operation

 MPLS network nodes are called Label-Switched Routers (LSRs)

 Use the label to determine the next-hop for the packet

 Do not need to examine the packet’s IP header

 Forwards packets based on the label

 After a path has been established:

 Packets destined to the same endpoint with the same requirements can

be forwarded based on these labels without a routing decision at every

hop

 Labels usually correspond to Layer 3 destination addresses, which

makes MPLS equivalent to destination-based routing 29

MPLS

Operation

 A Label-Switched Path (LSP) must be defined for each FEC before

packets can be sent

 Labels are locally significant to each MPLS node only

 Therefore nodes must communicate what label to use for each FEC

 Label Distribution Protocol

 Enhanced version of the Resource Reservation Protocol

 An interior routing protocol, such as OSPF or EIGRP is also used within the

MPLS network to exchange routing information 30

MPLS Operation

 Each of the MPLS nodes has previously communicated the labels it

uses for each of the defined FECs to its neighboring nodes

 Packet A and Packet B represent different flows; for example,

 Packet A might be from an FTP session, whereas

 Packet B is from a voice conversation

 Without MPLS, these packets would take the same route through

the network.

31

Note: Label allocation, label imposing, label swapping, and label popping usually happen in the service provider network, not the customer

(enterprise) network Customer routers never see a label.

MPLS

Features

 MPLS

 Only one examination of the packet

 Only one assignment to the FEC

 This is done at the MPLS ingress node

Service Provider Offerings

 VPNs:

 First built using leased lines with PPP and HDLC encapsulations

 Later, Layer 2 VPNs based on point-to-point data link layer connectivity,

using ATM or Frame Relay virtual circuits

 MPLS VPNs were introduced to provide a unified network for Layer 3

VPN services

 Any Transport over MPLS (AToM) was introduced to facilitate this Layer 2

connectivity across an MPLS backbone

34

Layer 2 and Layer 3 MPLS VPN Solutions

 Layer 2 MPLS VPN provides a Layer 2 service across the backbone

 R1 and R2 are connected together on the same IP subnet

 Layer 3 MPLS VPN provides a Layer 3 service across the backbone

 R1 and R2 are connected to ISP edge routers; on each side, a separate

IP subnet is used

35

 The network is divided into:

 Customer-controlled part (C-network)

 Provider-controlled part (P-network)

 Contiguous portions of C-network are called sites and are linked to the P-network

via Customer Edge routers (CE-routers)

 The CE-routers are connected to the PE-routers (Provider Edge routers)

 The core devices in the provider network (P-routers) provide transport across the provider backbone and do not carry customer routes

 The service provider connects customers using MPLS VPNs. 36

Site #3

Layer 2 and Layer 3 MPLS VPN Solutions

 Each customer is assigned an independent routing table - the virtual routing

and forwarding (VRF) table in the PE router.

 PE routers maintain separate routing tables for each customer

 Routing across the provider backbone is performed by another routing process that uses global IP routing table, the P-router

37

Site #3

Layer 2 and Layer 3 MPLS VPN Solutions

Layer 3 MPLS VPNs

 In a Layer 3 MPLS VPN, the following requirements must be met:

 The customer routers (the CE-routers) are not be MPLS VPN-aware

 Run standard IP routing software

 The provider core routers (the P-routers) must not carry customer (VPN)

routes, to make the MPLS VPN solution scalable

 The provider edge routers (PE-routers) must support MPLS VPN

services and traditional IP services

38

Layer 3 MPLS VPNs

 R1 and R2 are configured for EIGRP as if there were a corporate core

network between them

 EIGRP parameters between R1 and R2 (such as the AS number,

authentication password, and so on) are often governed/coordinated by the

Layer 3 MPLS VPNs

 R1 establishes an EIGRP neighbor relationship with the PE1 router,

 R2 establishes an EIGRP neighbor relationship with the PE2 router

 Routers R1 and R2 do NOT establish an EIGRP neighbor relationship with

each other

40

L3

Layer 2 MPLS VPNs

 Layer 2 MPLS VPN, an MPLS backbone provides a Layer 2 Ethernet

port-to-port connection between the two customer routers R1 and R2

 R1 and R2 are exchanging Ethernet frames

 PE1 router:

 Takes the Ethernet frame received from the directly connected R1

 Encapsulates it into an MPLS packet

 Forwards it across the backbone to the PE2 router

 The PE2 router decapsulates the MPLS packet and reproduces the Ethernet

frame on its Ethernet link to router R2

 This process is a type of AToM, called EoMPLS (a type of Metro Ethernet