Route Optimization - La Salleusers.salleurl.edu/~zaballos/CCNP/5.pdf · Route Optimization BSCI...
Transcript of Route Optimization - La Salleusers.salleurl.edu/~zaballos/CCNP/5.pdf · Route Optimization BSCI...
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 1
Route Optimization
BSCI Module 5
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 3 2
Seed Metrics and Route Redistribution
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 3
Using Multiple IP Routing Protocols
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 4
Redistribution with Seed Metric
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 5
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
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 3 6
Configuring and Verifying Route Redistribution
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 7
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>
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 8
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.
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� 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.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 10
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
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 11
Redistributing into RIP
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 12
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.
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 13
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>
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 14
Redistributing into OSPF
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 15
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]
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 16
� Bandwidth in kilobytes = 10000
� Delay in tens of microseconds = 100
� Reliability = 255 (maximum)
� Load = 1 (minimum)
� MTU = 1,500 bytes
Redistributing into EIGRP
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 17
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]
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 18
Redistributing into IS-IS
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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>
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 3 20
Route Redistribution Example
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Example: Before Redistribution
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Example: Before Redistribution (Cont.)
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 23
Example: Configuring Redistribution at Router B
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Example: Routing Tables After Route Redistribution
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 25
Example: Routing Tables After Summarizing Routes and Redistributions
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Modifying Administrative Distance
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 27
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.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 28
Good CCNP
Routing
Exam
Knowledge!
Administrative Distance
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 29
� 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
Administrative Distance
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 30
� 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
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 31
� 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
Changing Administrative Distance
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 32
� 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 rip
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
Changing Administrative Distance
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 3 33
Controlling Routing Update Traffic
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 34
Using the passive-interface Command
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 35
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.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 36
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.
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 37
Route FiltersLet’s take a look on how keep subnet 10.1.1.0 from
entering RTZ!
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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.
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 39
RTZ(config)#router rip
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
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 40
Inbound Route Filters (interface)
RTZ(config)#router rip
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
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 41
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]
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 42
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.
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 43
Outbound Route Filters (interface)
RTA(config)#router rip
RTA(config-router)#network 10.0.0.0
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
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 44
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 rip
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
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 45
“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)#network 10.0.0.0
RTA(config-router)#distribute-list 5 out s0
RTA(config-router)#exit
RTA(config)#access-list 5 deny any
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 46
Policy Based Routing
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 47
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.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 48
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
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 49
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.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 50
� 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.)
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 51
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.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 52
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
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 53
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.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 54
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
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 55
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
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 56
Examples
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Example: Redistribution Using Administrative Distance
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 58
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.)
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 59
Example: Redistribution Using Administrative Distance (Cont.)
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Example: Redistribution Using Administrative Distance
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Example: Redistribution Using Administrative Distance (Cont.)
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
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 62
Example: Redistribution Using Administrative Distance (Cont.)
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
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 63
Example: Redistribution Using Administrative Distance (Cont.)
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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
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 3 65
Configuring DHCP
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DHCP in an Enterprise Network
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DHCP protocol
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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.
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� 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.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 70
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.
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 71
Importing and Autoconfiguration
RemoteRouter(config-dhcp)#import all
� Used to import DHCP option parameters from a
centralized DHCP server. Used for remote DHCP pools.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 72
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
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 73
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.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 74
IP helper address
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 75
Relay Agent Option Support
Router (config)# ip dhcp relay information option
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 76
Q and A
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© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 5 77