CCNP Route 642-902 Implementing Cisco IP Routing

·To use GNS3 you first need to provide your own copy of a network operating system, like Cisco IOS, PIX, ASA, IPS or Juniper JunOS.

·You can download GNS3 software from http://www.gns3.net/download/ …

• It is the process of combining smaller networks in to single large sub network (Combining the contagious address into one and send to neighbor.)
• It helps in reducing the size of routing table.

Advantages

·Minimizing the routing table.

·Less use of resources like memory, processor, bandwidth.

Two Type of Summarization

·Auto summary

·Manual summary

AUTO SUMMARY

·Summarization is done to a default class full boundary

§A /8

§B /16

§C /24

·Class full routing protocol does auto summary by default and it can’t be disabled

·Routing protocol like RIPv2, EIGRP, BGPv4 support auto summary and can be disabled

·Routing protocol like OSPF and ISIS doesn’t support auto summary

Disadvantages of Auto-summary:

·Can create Problems if the network is in discontiguous Subnets.

·Not always applicable

To enable or disable auto summary

Router(config-router)# [no] auto-summary

Manual summary

·Administrator manually configures Summarization

·It is supported by all classless routing protocols

In this Video you get Introduced to EIGRP from basics

Verifying the EIGRP Process discussed in the previous video using some of the debug commands

• Metric (32 bit) : Composite Metric (BW + Delay + load + MTU + reliability )

CONFIGURING EIGRP FOR IP

Router(config)# router EIGRP

Router(config-router)#network network-id [wildcard-mask]

FD of current successor route > AD of feasible successor

Feasible Successor= Second best AD < FD of Successor

EIGRP supports both

1.equal-cost load balancing

2.unequal-cost load balancing

·Routes with lowest equal metric are installed in the routing table by default

·When a router learns a same route from different neighbors with the same metric it install both the routes in the routing table and does load balancing, this is called equal cost load balancing.

·Note:- It does equal cost load balancing automatically. whereas unequal cost is not automatic.

·For unequal cost load balancing we need to enable "variance"

·EIGRP can load share up to six paths. (The default is four paths)

EIGRP Unequal-Cost Load Balancing Allows the router to include routes with a metric smaller than the multiplier value times the metric of successor

·Variance is configured for unequal cost load balancing

·Variance is the multiplier to FD of successor

·Default is 1(equal cost load balancing)

Router(config)# router eigrp 100

Router(config-router)# variance

EIGRP STUB

• Stub routingis one way to limit queries. A stub router is one that is connected to no more than two neighbors and should never be a transit router.
• The EIGRP stub routing feature improves network stability, reduces resource utilization, and simplifies remote router (spoke) configuration.
• Stub routing is commonly used in a hub-and-spoke topology.
• A stub router sends a special peer information packet to all neighboring routers to report its status as a stub router.
• A neighbor that receives a packet informing it of the stub status does not query the stub router for any routes.

Configuring EIGRP Stub

Router(config-router)# EIGRP stub [receive-only|connected|static|summary]

·receive-only: Prevents the stub from sending any type of route.

·connected: Permits stub to send connected routes
(may still need to redistribute).

·static: Permits stub to send static routes
(must still redistribute).

·summary: Permits stub to send summary routes.

Default is connected and summary.

IN this video I explained why we need to inject default route in to IGP protocols

IN this video I explained how to inject default route in to EIGRP

IN this video I explained how to inject default route in to RIPv2

IN this video I explained how to inject default route in to OSPF

In this lecture you will understand the basic Process of OSPF 7 stages when you configure OSPF for the first time

In this Lecture we will discuss on the concept of Areas in OSPF and how to design some big complex networks using OSPF areas

Redistribution

The process of exchanging routing information between different routing protocols

When we use multiple protocol

• Application-specific protocols

• Mismatch between devices (Vendors)

• Political boundaries

ØUsing multiple IP routing protocols can be a result of migrating to a more advanced routing protocol, a multivendor environment, political boundaries, or device mismatch.

ØRoute redistribution is possible between any two IP routing protocols.

ØInternal routes are routes advertised with in the same protocol

Ø External routes are routes which gets redistributed .

OSPF Virtual Link

·Virtual links are used to connect a discontiguous area to area 0

·A logical connection is built between routers

·Virtual links are recommended for backup or temporary connections

Configuring Virtual Links :

Router(config)#router ospf

Router(config-router)#areavirtual-link

OSPF NETWORK TYPES

Adjacency Behavior for a Broadcast Multi Access networks

·Generally these are, LAN technologies like Ethernet and Token Ring.

·DR and BDR selection are required.

·OSPF detects this type of link automatically.

·All neighbor routers form full adjacencies with the DR and BDR only.

Designated Router &Backup Designated Router

·The router having highest priority is DR

·The router with second-highest priority is BDR

·The default priority value is 1

·In the case of a tie, router with highest router ID is DR second highest router ID becomes the BDR

·If router priority is 0 it cannot become the DR or BDR

·Router which is not a DR or BDR is called as DROTHER

·DR & BDR election is not preemptive

Router(config)#interface

Router(config-if)#ip ospf priority number

• The above interface configuration command assigns the OSPF priority to an interface.
• Different interfaces on a router may be assigned different values.
• The default priority is 1. The range is from 0 to 255.

DR/BDR Elections Neighbors

DR/BDR →DROTHER → Full

DROTHER → DR/BDR → Full

DROTHER → DROTHER → 2 Way

Updates

DROTHER → DR/BDR → 224.0.0.6

DR → DROTHER → 224.0.0.5

Stub Areas

·External LSAs are stopped ( E1 and E2 routes)

·Default route is advertised into stub area by the ABR

·All routers in stub area must be configured as stub

Configuring all routers of Totally Stubby Area

Router(config-router)#area stub

Configuring Area Border Router of Totally Stubby AreaRouter

(config-router)#area stubno-summary

Features of IPv6

–Larger Address Space

–Aggregation-based address hierarchy

–Efficient backbone routing

–Efficient and Extensible IP datagram

–Stateless Address Autoconfiguration

–Security (IPsec mandatory)

–Mobility

Assigning the IPV6 address

1)Static

2)Autoconfiguration

a.Statefull ( via DHCP)

b.Stateless ( device gets IP IPv6 add by including the MAC add )

STATIC & DEFAULT ROTUING

IPv6 support static and default routing and the working principle ( when to use and how it works is same what we learned in IPV4 routing )

·Syntax for writing static and default routing is similar in IPV6 when compared with IPV4

·As in IPv4, IPv6 has 2 families of routing protocols: IGP and EGP, and still uses the longest-prefix match routing algorithm

OSPFv3

·Based on OSPFv2, with enhancements

oDistributes IPv6 prefixes

oRuns directly over IPv6

oShips in the night with OSPFv2

·Adds IPv6-specific attributes:

o128-bit addresses

oLink-local address

oMultiple addresses and instances per interface

oAuthentication (now uses IPsec)

oOSPFv3 runs over a link, rather than a subnet

EIGRP FOR IPv6

·Same EIGRP used with IPv4

·Best of distance vector and link state (advanced distance vector)

·Multiprotocol EIGRP has a protocol-dependent module for IPv4, IPX, AppleTalk, and now IPv6

·Easy to configure and fast convergence

Why do we need Route Filtering Methods

}You might need to control exactly which routes are advertised or redistributed, or which paths are chosen.

}Advertise only some specific Routes to Neighbor

}Redistribute Specific Routes

}Path Manipulation of some specific Routes

}Changing Metric and Metric-type for specific routes

}Changing The Administrative Distance for Specific Routes

}With BGP

◦Controlling routes to be advertised to ISP

◦Control routes to get in to routing table

}Policy Based Routing

ways to control routing updates

}Cisco IOS provides several ways to control routing updates:

◦Passive Interface

◦Distribute Lists

◦Prefix Lists

◦Route Maps

PASSIVE INTERFACE

Passive-interface command is used in all routing protocols to disable sending updates out from a specific interface. However the command behavior varies from o­ne protocol to another.

Passive Interface in RIPv2

·In RIP this command will disable sending multicast updates via a specific interface but will allow listening to incoming updates from other RIP speaking neighbors.

·This simply means that the router will still be able to receive updates o­n that passive interface and use them in the routing table.

Router(config)#router EIGRP 100

Router(config-router)#passive-interface s1/0

Router(config)#router OSPF 1

Router(config-router)#passive-interface s1/0

Using Distribution lists

·A distribute-list is used to control routing updates either

ocoming TO your router

oor leaving FROM your router.

·Distribute-lists work on a variety of different IOS routing protocols.

·One of the easiest way

·Use an access list (or route map Or Prefix-list ) to permit or deny routes.

·Can be applied to transmitted, received, or redistributed routing updates.

Configuring Distribute-list

Router(config-router)# distribute-list

Configuring Distribute-list

Router(config-router)# distribute-list

Using IP Prefix-list

}The IOS IP prefix-list another tool for matching routes.

}match two components of an IP route:

◦The route prefix (the subnet number)

◦The prefix length (the subnet mask)

}The command then sets either a deny or permit action for each matched prefix/length.

}Prefix lists work very similarly to access lists;

}a prefix list contains one or more ordered entries which are processed sequentially.

}The evaluatioqn of a prefix against a prefix list ends as soon as a match is found.

}To create a prefix list or add a prefix-list entry, use the ip prefix-list command in global configuration mode. To delete a prefix-list entry, use the no form of this command.

◦ip prefix-list list-name | list-number [seq number] {deny network/length | permit network/length}[ge length] [le length]

◦ip prefix-list list-name | list-number [seq number] {deny network/length | permit network/length}[ge length] [le length]

Route-maps

}Route maps are similar to a scripting language for these reasons:

}They work like a more sophisticated access list.

}They offer top-down processing.

}Once there is a match, leave the route map.

}Lines are sequence-numbered for easier editing

}Insertion of lines ,Deletion of lines

}Route maps are named rather than numbered for easier documentation.

}Match criteria and set criteria can be used, similar to the “if, then” logic in a scripting language.

}The common uses of route maps are as follows:

◦Redistribution route filtering: a more sophisticated alternative to distribute lists

◦Policy-based routing: the ability to determine routing policy based on criteria other than the destination network

◦BGP policy implementation: the primary tool for defining BGP routing policies

Configure Route Map

Router(config)# Route-map permit/deny

Defining the condition to Match

Router(config-route-map)#match

Defining the condition to Set

Router(config-route-map)#set

match conditions used in redistribution:

match interface

match ip address [ACL]

match ip next-hop

match ip route-source

match metric

match route-type

set operations used in redistribution:

set level {level-1 | level-2 | level-1-2 | stub-area | backbone} (OSPF/IS-IS)

set metric

set metric-type {internal | external | type-1 | type-2}

POLICY -BASED ROUTING

ØIt is used for implementing policy that cause the packet to take a different direction

ØPBR allows source based routing

ØRouting table is destination base

ØPBR can be used for making type of service tag

ADVANTAGES

ØDifferent users can go from different directions

ØLoad sharing

ØPBR will be implemented on the incoming direction of the source interface

ØIf the packet is match in the route map and it is permit it will be send according to the policy

ØIf the packet is match in the route map and route map deny packet will be forwarded according to normal routing table

Introduction to BGP

·BGP is the only routing protocol in widespread use which facilitates inter-domain routing (between autonomous systems).

·BGP is path-vector; routes are tracked in terms of which autonomous systems they pass through.

·BGP attributes allow granularity in path selection.

When to use BGP

BGP is more appropriate if one of the following conditions exist

§A.S. working as transit A.S. (Ex. ISP)

§A.S. connected to multiple A.S.

§Data traffic path entering or leaving A.S. need to manipulated

When not to use BGP

BGP is not recommended if one or more following condition exist

§If it is Single-home A.S

§Lack of recourses like memory and less processing power in routers

§Low bandwidth link between A.S

§Limited understanding about BGP route filtering and path selection processes

Types of ISP Connections

Single Homed

Dual-homed site

Multihoming

Dual Multihomed

BGP Neighbors

·BGP neighbors are routers forming TCP connection for exchanging BGP updates. Also called as BGP Peers or BGP Speakers.

·Two type of BGP neighbor relationship.

§IBGP

§EBGP

·Configuration parameters such as neighbor IP addresses and their AS number, and which networks you will advertise via BGP

Router(config)# router bgp

Router(config-router)# network [mask ]

Router(config-router)# neighbor remote-as

Configuring BGP Authentication on Cisco IOS:

·Border Gateway Protocol (BGP) supports authentication mechanism using Message Digest 5 (MD5) algorithm.

·When authentication is enabled, any Transmission Control Protocol (TCP) segment belonging to BGP exchanged between the peers is verified and accepted only if authentication is successful.

·For authentication to be successful, both the peers must be configured with the same password.

·If authentication fails, the BGP neighbor relationship is not be established.

Router(config-router)#neighbor {ip-address | peer-group-name} <password string>

Peer groups

·Peer groups are defined to efficiently apply same policies to multiple neighbors:

·Peer groups are useful when many neighbors have the same outbound policies.

·Members can have a different inbound policy.

·Updates are generated once per peer group.

·Configuration is simplified.

Router(config-router)# neighbor peer-group

This command creates a peer group.

Router(config-router)# neighbor < peer-group peer-group-name>

In order to get the routes to be learned we have two Solutions:

1.Full mesh neighborship ( which the requirement says not to use here )

2.Route reflector

To Configure Route-reflector

·All Clients should establish neigbbor with only servers

·Clients will not establish neigbor with any other clinet

·In case if you have 2 servers ( server establish neigbbor with other servers and clients )

When EBGP ---sends an update to another EBGP neighbor -------------changes the next hop

When IBGP ---sends an update to another IBGP neighbor ------------- the next hop remains same (not change)

Synchronization rule:

·Do not use or advertise to an external neighbor a route learned by IBGP until a matching route has been learned from an IGP

·Ensures consistency of information throughout the AS.

·Safe to have it off only if all routers in the transit path in the AS are running full-mesh IBGP;

·off by default in Cisco IOS software release 12.2(8)T and later

·BGP synchronization is often disabled for autonomous systems which do not act as a transit AS.

·Safe to have it off only if all routers in the transit path in the AS are running full-mesh IBGP; off by default in Cisco IOS software release 12.2(8)T and later

Router (config-router)# no synchronization

·The above command Disables BGP synchronization so that a router will advertise routes in BGP without learning them in an IGP

Router (config-router)# synchronization

BGP ATTRIBUTES

BGP chooses a route to a network based on the attributes of its path. Four categories of attributes exist as follows:

·Well-known mandatory:

oMust be recognized by all BGP routers, present in all BGP updates, and passed on to other BGP routers. For example, AS path, origin, and next hop.

·Well-known discretionary:

oMust be recognized by all BGP routers and passed on to other BGP routers but need not be present in an update, for example, local preference.

·Optional transitive:

oMight or might not be recognized by a BGP router but is passed on to other BGP routers.

oIf not recognized, it is marked as partial, for example, aggregator, community.

·Optional non-transitive:

oIf the BGP process does not recognize the attribute then it can ignore the update and not advertise the path to its peers

ofor example, Multi-Exit Discriminator (MED), originator ID.

WEIGHT

·Weight is Cisco’s attribute.

·Tells how to exit the AS

·Path with the highest weight is more desirable.

·Local to the router ( not advertise to the other routers in the AS )

·Weight is partial attribute.

·Default weight = 0 for learned routes, 32,768 for locally injected routes)

LOCAL PREFERENCE

·Local preference defines how data traffic should exit from an AS.

·Path with highest preference value is more desirable.

·It is advertised only to IBGP neighbor within an AS.

·Default value is 100

·Local preference is well known, discretionary attribute.

Route Selection Decision Process

Consider only (synchronized) routes with no AS loops and a valid next hop, and then:

1. Prefer highest weight (local to router).
2. Prefer highest local preference (global within AS).
3. Prefer route originated by the local router (next hop = 0.0.0.0).
4. Prefer shortest AS path.
5. Prefer lowest origin code (IGP < EGP < incomplete) i > E > ? .
6. Prefer lowest MED (exchanged between autonomous systems).
7. Neighbor Type (Prefer eBGP over iBGP)
8. IGP metric to NEXT_HOP (Smaller value preferred)
9. Prefer oldest route for EBGP paths.
10. Prefer the path with the lowest neighbor BGP router ID.
11. Prefer the path with the lowest neighbor IP address.