Route Optimization - La Salleusers.salleurl.edu/~zaballos/CCNP/5.pdf · Route Optimization BSCI...

1

© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 1

Route Optimization

BSCI Module 5


Seed Metrics and Route Redistribution

2


Using Multiple IP Routing Protocols


Redistribution with Seed Metric

3


Default Seed Metrics

BGP metric is set to IGP metric valueBGP

0IS-IS

20 for all except BGP, which is 1OSPF

InfinityIGRP/EIGRP

InfinityRIP

Default Seed MetricsProtocol


Configuring and Verifying Route Redistribution

4


Redistribution Supports All Protocols

RtrA(config)#router ripRtrA(config-router)#redistribute ?bgp Border Gateway Protocol (BGP)connected Connectedeigrp Enhanced Interior Gateway Routing Protocol (EIGRP)isis ISO IS-ISiso-igrp IGRP for OSI networksmetric Metric for redistributed routesmobile Mobile routesodr On Demand stub Routesospf Open Shortest Path First (OSPF)rip Routing Information Protocol (RIP)route-map Route map referencestatic Static routes<cr>


Planning Redistribution

� Locate the boundary router between two routing processes.

� Determine which routing process is the core or backbone process

� Determine which routing process is the edge or migration process

� Select a method for injecting the required edge protocol routes into the core.

5


� Use this command to redistribute routes into RIP:

Router(config-router)# redistribute protocol

[process-id] [match route-type] [metric metric-

value] [route-map map-tag]

Configuring Redistribution into RIP

RtrA(config)# router ripRtrA(config-router)# redistribute ospf ?

<1-65535> Process IDRtrA(config-router)# redistribute ospf 1 ?

match Redistribution of OSPF routesmetric Metric for redistributed routesroute-map Route map reference…<cr>

� Default metric is infinity.


Router(config-router)# redistribute protocol [process-id]

{level-1 | level-1-2 | level-2} [metric metric-value]

[metric-type type-value] [match {internal | external 1| external 2}] [tag tag-value] [route-map map-tag]

[weight weight] [subnets]

� Redistribute static [ip]:

It is used to redistribute IP static routes.

The optional ip keyword is used when redistributing into the Intermediate System-to-Intermediate System (IS-IS) protocol.

� Redistribute connected:

It refers to routes that are established automatically by virtue of having enabled IP on an interface.

� (Optional) metric:

Used for the redistributed route. If a value is not specified for this option, and no value is specified using the default-metric command, the default metric value is 0 for IS-IS and 20 for OSPF.

� (Optional) metric-type

For OSPF. It can : 1-Type 1 external route, 2-Type 2 external route

Redistribute command

6


Redistributing into RIP


Configuring Redistribution into OSPF

� Use this command to redistribute routes into OSPF:

Router(config-router)# redistribute protocol

[process-id] [metric metric-value] [metric-typetype-value] [route-map map-tag] [subnets] [tag

tag-value]

� Default metric is 20.

� Default metric type is 2.

� Subnets do not redistribute by default.

7


Example: Redistribution into OSPF

RtrA(config)# router ospf 1RtrA(config-router)# redistribute eigrp ?

<1-65535> Autonomous system numberRtrA(config-router)# redistribute eigrp 100 ?

metric Metric for redistributed routesmetric-type OSPF/IS-IS exterior metric type for

redistributed routesroute-map Route map referencesubnets Consider subnets for redistribution into OSPFtag Set tag for routes redistributed into OSPF…<cr>


Redistributing into OSPF

8


Configuring Redistribution into EIGRP

RtrA(config)# router eigrp 100RtrA(config-router)# redistribute ospf ?

<1-65535> Process IDRtrA(config-router)# redistribute ospf 1 ?

match Redistribution of OSPF routesmetric Metric for redistributed routesroute-map Route map reference

…<cr>

� Default metric is infinity.

� Use this command to redistribute routes into EIGRP:

router(config-router)# redistribute protocol

[process-id] [match {internal | external 1 |external 2}] [metric metric-value] [route-mapmap-tag]


� Bandwidth in kilobytes = 10000

� Delay in tens of microseconds = 100

� Reliability = 255 (maximum)

� Load = 1 (minimum)

� MTU = 1,500 bytes

Redistributing into EIGRP

9


Configuring Redistribution into IS-IS

RtrA(config)# router isisRtrA(config-router)# redistribute eigrp 100 ?

level-1 IS-IS level-1 routes onlylevel-1-2 IS-IS level-1 and level-2 routeslevel-2 IS-IS level-2 routes onlymetric Metric for redistributed routesmetric-type OSPF/IS-IS exterior metric type for redistributed routesroute-map Route map reference..Output Omitted

� Routes are introduced as level 2 with a metric of 0 by default.

� Use this command to redistribute routes into IS-IS:

router(config-router)# redistribute protocol

[process-id] [level level-value] [metricmetric-value] [metric-type type-value] [route-map map-tag]


Redistributing into IS-IS

10


Redistributing IS-IS into Other Protocols

Router(config)# router ospf 1Router(config-router)# redistribute isis ?<output omitted>

level-1 IS-IS level-1 routes onlylevel-1-2 IS-IS level-1 and level-2 routeslevel-2 IS-IS level-2 routes only

<output omitted>


Route Redistribution Example

11


Example: Before Redistribution


Example: Before Redistribution (Cont.)

12


Example: Configuring Redistribution at Router B


Example: Routing Tables After Route Redistribution

13


Example: Routing Tables After Summarizing Routes and Redistributions


Modifying Administrative Distance

14


Administrative Distance

� A routing protocol’s administrative distance rates its trustworthiness as a source of routing information.

It is an integer from 0 to 255.

The lowest administrative distance has the highest trust rating.

An administrative distance of 255255 means the routing routing information source cannot be trusted at all and should be information source cannot be trusted at all and should be ignoredignored.

An administrative distance of zerozero is reserved for connected reserved for connected interfaces, and will always be preferredinterfaces, and will always be preferred.


Good CCNP

Routing

Exam

Knowledge!


15


� When using multiple IP routing protocols on a router, the default distances almost always suffice.

� However, some circumstances call for changing the administrative distance values on a router.

� If, for example, a router is running both IGRP and OSPF, it may receive routes to the same network from both protocols.

� The default administrative distances favor IGRP routes over OSPF routes:

I 10.0.0.0 [100/10576] via 192.168.0.1, Serial0

0 10.0.0.0 [110/192] via 172.17.0.1, Serial1

IGRP at 100 favored



� But since IGRP doesn’t support CIDR, you may want the router to use the OSPF route instead.

� In this case, you can configure the local router to apply a custom administrative distance to all OSPF routes:

RTZ(config)#router ospf 1

RTZ(config-router)#distance 95

I 10.0.0.0 [100/10576] via 192.168.0.1, Serial0

0 10.0.0.0 [ 95/192] via 172.17.0.1, Serial1

OSPF at 95 now favored

Changing Administrative Distance

16


� You can also apply the distance command with optional arguments to make changes to selected routes based on where they originate.

� The expanded syntax of the distance command is as follows:

Router(config-router)#distance weight [source-ip-addresssource-mask (access-list-number | name)]

� For example, we can configure a router to apply an administrative distance of 105 to all RIP routes received from 10.4.0.2.

� These values are local to the router, all other routers will apply the administrative distance of 120.

RTZ(config)#router rip

RTZ(config-router)#distance 105 10.4.0.2 255.255.255.0



� Or, we can configure a router to apply an administrative distance of 97 to specific RIP routes, 192.168.3.0, received from 10.3.0.1.


RTZ(config-router)#distance 97 10.3.0.1 255.255.255.0 2

RTZ(config-router)#exit

RTZ(config)#access-list 2 permit 192.168.3.0 0.0.0.255

Source of the route

The route that will get the

administrative distance of 97


17


Controlling Routing Update Traffic


Using the passive-interface Command

18


Passive Interfaces

The passive-interface command works differently with the different IP routing protocols that support it.

RIP/IGRP: Can receive updates but doesn’t send.

OSPF: Routing information is neither sent nor received via a passive interface.

OSPF: The network address of the passive interface appears as a stub network in the OSPF domain.

EIGRP: the router stops sending hello packets on passive interfaces.

When this happens, the EIGRP router can’t form neighbor adjacencies on the interface or send and receive routing updates.


Route Filters

� Configuring an interface as passive prevents it from sending updates entirely

� There are times when you need to suppress only certain routes in the update from being sent or received.

� We can use a distribute-list command to pick and choose what routes a router will send or receive updates about.

� The distribute-list references an access-list, which creates a route filter – a set of rules that precisely controls what routes a router sends or receives in a routing update.

19


Route FiltersLet’s take a look on how keep subnet 10.1.1.0 from

entering RTZ!


Route Filters

Inbound interfaces:

� When applied to inbound updates, the syntax for configuring a route filter is:

Router(config-router)#distribute-list access-list-

number in [interface-name]

Note: This does not permit/deny packets from entering the routers, only what routes a router will send or receive updates about.

20



RTZ(config-router)#network 10.0.0.0

RTZ(config-router)#distribute-list 16 in

RTZ(config)#access-list 16 deny 10.1.1.0 0.0.0.255

RTZ(config)#access-list 16 permit any

Inbound Route Filters (global)

Applies to all interfaces


Inbound Route Filters (interface)


RTZ(config-router)#network 10.0.0.0

RTZ(config-router)#distribute-list 16 in s0

RTZ(config)#access-list 16 deny 10.1.1.0 0.0.0.255

RTZ(config)#access-list 16 permit any

Applies to just S0 interface

21


Route Filters

Outbound interfaces:

� When applied to outbound updates, the syntax can be more complicated:

Router(config-router)#distribute-list access-list-

number out [interface-name | routing-process | as-number]


Outbound Route Filters (global)

RTA(config)#router rip

RTA(config-router)#network 10.0.0.0

RTA(config-router)#distribute-list 24 out

RTA(config)#access-list 24 deny 10.1.1.0 0.0.0.255

RTA(config)#access-list 24 permit any

Applies to all interfaces

Applies to all

interfaces although

this graphic only

shows S2.

22


Outbound Route Filters (interface)

RTA(config)#router rip


RTA(config-router)#distribute-list 24 out s2

RTA(config)#access-list 24 deny 10.1.1.0 0.0.0.255

RTA(config)#access-list 24 permit any

Applies to just S2 interface


Route Filters

For each interface and routing process, Cisco IOS permits one incoming global, one outgoing global, one incoming interface, and one outgoing interface distribute-list:


RTZ(config-router)#distribute-list 1 in

RTZ(config-router)#distribute-list 2 out

RTZ(config-router)#distribute-list 3 in e0

RTZ(config-router)#distribute-list 4 out e0

23


“Passive” EIGRP interfaces

� A passive interface can’t send EIGRP hellos, which thus prevents adjacency relationships with link partners.

� An administrator can create a “pseudo” passive EIGRP interface by using a route filter that suppresses allroutes from the EIGRP routing update.

RTA(config)#router eigrp 364


RTA(config-router)#distribute-list 5 out s0

RTA(config-router)#exit

RTA(config)#access-list 5 deny any


Policy Based Routing

24


Route Maps

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

� They work like a more sophisticated access list:

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.


Route Map Applications

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

25


route-map my_bgp permit 10{ match statements }{ match statements }{ set statements }{ set statements }

route-map my_bgp deny 20:: :: :::: :: ::

route-map my_bgp permit 30:: :: :::: :: ::

Route Map Operation

� A list of statements composes a route map.

� The list is processed top-down like an access list.

� The first match found for a route is applied.

� The sequence number is used for inserting or deleting specific route map statements.


� The match statement may contain multiple references.

� Multiple match criteria in the same line use a logical OR.

� At least one reference must permit the route for it to be a candidate for redistribution.

� Each vertical match uses a logical AND.

� All match statements must permit the route for it to remain a candidate for redistribution.

� Route map permit or deny determines if the candidate will be redistributed.

Route Map Operation (Cont.)

26


The match Command

router(config-route-map)#

match {options}

options :ip address ip-access-listip route-source ip-access-listip next-hop ip-access-listinterface type number

metric metric-valueroute-type [external | internal | level-1 | level-2 |local]

…

� The match commands specify criteria to be matched.

� The associated route map statement permits or denies the matching routes.


The match commands

Matches tag of a routematch tag

Matches routes of the specified typematch route-type

Matches routes with the metric specifiedmatch metric

Matches based on the layer 3 length of a packetmatch length

Matches any routes that have a next-hop router address that is passed by one of the ACLs specified

match ip next-hop

Matches routes that have been advertised by routers and access servers at the address that is specified by the ACLs

match ip route-source

Matches any routes that have a destination network number address that is permitted by a standard or extended ACL

match ip address

Matches any routes that have the next hop out of one of the interfaces specified

match interface

Matches a BGP communitymatch community

DescriptionCommand

27


The set Command

router(config-route-map)#

set {options}options :metric metric-valuemetric-type [type-1 | type-2 | internal | external]level [level-1 | level-2 | level-1-2 |stub-area | backbone]ip next-hop next-hop-address

� The set commands modify matching routes.

� The command modifies parameters in redistributed routes.


The set commands

Specifies the BGP weight valueset weight

Sets tag value for destination routing protocolset tag

Sets the metric type for the destination routing protocolset metric-type

Sets the metric value for a routing protocolset metric

Specifies a BGP local preference value set local-preference

Indicates where to import routes for IS-IS and OSPFset level

Indicates where to output packets that pass a match clause of a route map for policy routing

set ip next-hop

Indicates where to output packets that pass a match clause of a route map for policy routing and for which the Cisco IOS software has no explicit route to a destination

set ip default next-hop

Indicates where to output packets that pass a match clause of a route map for policy routing and have no explicit route to the destination

set default interface

Indicates where to output packets that pass a match clause of a route map for policy routing

set interface

Sets the BGP communities attributeset community

Computes automatically the tag valueset automatic-tag

Modifies an AS path for BGP routesset as-path

DescriptionCommand

28


Route Maps and Redistribution CommandsRouter(config)# router ospf 10Router(config-router)# redistribute rip route-map redis-rip

Router(config)#route-map redis-rip permit 10 match ip address 23 29set metric 500set metric-type type-1

route-map redis-rip deny 20match ip address 37

route-map redis-rip permit 30set metric 5000set metric-type type-2

� Routes matching either access list 23 or 29 are redistributed with an OSPF cost of 500, external type 1.

� Routes permitted by access list 37 are not redistributed.

� All other routes are redistributed with an OSPF cost metric of 5000, external type 2.

Router(config)#access-list 23 permit 10.1.0.0 0.0.255.255access-list 29 permit 172.16.1.0 0.0.0.255access-list 37 permit 10.0.0.0 0.255.255.255


Examples

29


Example: Redistribution Using Administrative Distance


router ospf 1

redistribute rip metric 10000 metric-type 1 subnets

network 172.31.0.0 0.0.255.255 area 0

!

router rip

version 2

redistribute ospf 1 metric 5

network 10.0.0.0

no auto-summary

router ospf 1

redistribute rip metric 10000 metric-type 1 subnets

network 172.31.3.2 0.0.0.0 area 0

!

router rip

version 2

redistribute ospf 1 metric 5

network 10.0.0.0

no auto-summary

Router P3R1

Router P3R2

Example: Redistribution Using Administrative Distance (Cont.)

30




Example: Redistribution Using Administrative Distance

31



hostname P3R1!router ospf 1redistribute rip metric 10000 metric-type 1 subnetsnetwork 172.31.0.0 0.0.255.255 area 0distance 125 0.0.0.0 255.255.255.255 64 !router ripversion 2redistribute ospf 1 metric 5network 10.0.0.0no auto-summary!access-list 64 permit 10.3.1.0 0.0.0.255access-list 64 permit 10.3.3.0 0.0.0.255access-list 64 permit 10.3.2.0 0.0.0.255access-list 64 permit 10.200.200.31access-list 64 permit 10.200.200.34access-list 64 permit 10.200.200.32access-list 64 permit 10.200.200.33

hostname P3R2!router ospf 1redistribute rip metric 10000 metric-type 1 subnetsnetwork 172.31.3.2 0.0.0.0 area 0distance 125 0.0.0.0 255.255.255.255 64!router ripversion 2redistribute ospf 1 metric 5network 10.0.0.0no auto-summary!access-list 64 permit 10.3.1.0 0.0.0.255access-list 64 permit 10.3.3.0 0.0.0.255access-list 64 permit 10.3.2.0 0.0.0.255access-list 64 permit 10.200.200.31access-list 64 permit 10.200.200.34access-list 64 permit 10.200.200.32access-list 64 permit 10.200.200.33



hostname P3R1!router ospf 1redistribute rip metric 10000 metric-type 1 subnetsnetwork 172.31.0.0 0.0.255.255 area 0distance 125 0.0.0.0 255.255.255.255 64 !router ripversion 2redistribute ospf 1 metric 5network 10.0.0.0no auto-summary!access-list 64 permit 10.3.1.0 0.0.0.255access-list 64 permit 10.3.3.0 0.0.0.255access-list 64 permit 10.3.2.0 0.0.0.255access-list 64 permit 10.200.200.31access-list 64 permit 10.200.200.34access-list 64 permit 10.200.200.32access-list 64 permit 10.200.200.33

hostname P3R2!router ospf 1redistribute rip metric 10000 metric-type 1 subnetsnetwork 172.31.3.2 0.0.0.0 area 0distance 125 0.0.0.0 255.255.255.255 64!router ripversion 2redistribute ospf 1 metric 5network 10.0.0.0no auto-summary!access-list 64 permit 10.3.1.0 0.0.0.255access-list 64 permit 10.3.3.0 0.0.0.255access-list 64 permit 10.3.2.0 0.0.0.255access-list 64 permit 10.200.200.31access-list 64 permit 10.200.200.34access-list 64 permit 10.200.200.32access-list 64 permit 10.200.200.33

32




Know Your Network

� Be very familiar with your network BEFORE implementing redistribution

� Focus on routers with redundant paths

� Make sure no path information is lost when using the distance command

33


Configuring DHCP


DHCP in an Enterprise Network

34


DHCP protocol


Configuring an Cisco IOS DHCP Server

Router(config)#ip dhcp pool [pool name]

� Enable a DHCP pool for use by hosts.

Router(config-dhcp)#default-router [host address]

� Specify the default router for the pool to use.

Router(config-dhcp)#network [network address][subnet mask]

� Specify the network and subnet mask of the pool.

Router(config)#ip dhcp excluded-address low-address high-address

� Specify the IP address that should not assign to

DHCP clients.

35


� Specifies the IP address of a DNS server that is available

to a DHCP client. One is required, but up to eight can be

specified.

Optional DHCP Server Commands

Router(config-dhcp)#domain-name domain

� Specifies the domain name for the client.

Router(config-dhcp)#netbios-name-server address

� Same as DNS, but for WINS.

Router(config-dhcp)#dns-server address

Router(config-dhcp)#lease {days [hours] [minutes] | infinite}

� Specifies the duration of the lease. The default is a one-

day lease.


DHCP Database Command and Configuration

ip dhcp database ftp://user:[email protected]/router-dhcp write-delay 120

ip dhcp excluded-address 172.16.1.100 172.16.1.103

ip dhcp excluded-address 172.16.2.100 172.16.2.103

ip dhcp pool 0

network 172.16.0.0/16

domain-name global.com

dns-server 172.16.1.102 172.16.2.102

netbios-name-server 172.16.2.103 172.16.2.103

default-router 172.16.1.100

Router(config)#ip dhcp database url [timeout seconds | write-delay seconds]

� Configures the database agent and the interval between

database updates and database transfers.

36


Importing and Autoconfiguration

RemoteRouter(config-dhcp)#import all

� Used to import DHCP option parameters from a

centralized DHCP server. Used for remote DHCP pools.


Importing and Autoconfiguration (Cont.)

ip dhcp-excluded address 10.0.0.1 10.0.0.5ip dhcp pool central

network 10.0.0.0 255.255.255.0default-router 10.0.0.1 10.0.0.5domain name central.comdns-server 10.0.0.2netbios-name-server 10.0.0.2

interface fastethernet0/0ip address 10.0.0.1 255.255.255.0

ip dhcp-excluded address 20.0.0.2ip dhcp pool client

network 20.0.0.0 255.255.255.0default-router 20.0.0.2import all

interface fastethernet0/0ip address dhcp

37


DHCP Client

ip dhcp-excluded address 20.0.0.2ip dhcp pool client

network 20.0.0.0 255.255.255.0default-router 20.0.0.2import all

interface fastethernet0/0ip address dhcp

Router (config-if)#

ip address dhcp

Enables an IOS device to obtain an IP address

dynamically from a DHCP server.


IP helper address

38


Relay Agent Option Support

Router (config)# ip dhcp relay information option


Q and A

39


Route Optimization - La Salleusers.salleurl.edu/~zaballos/CCNP/5.pdf · Route Optimization BSCI...

Documents

Transcript of Route Optimization - La Salleusers.salleurl.edu/~zaballos/CCNP/5.pdf · Route Optimization BSCI...