- About Cisco IOS Documentation
- Chapter 1, Overview
- Chapter 2, CTC Operations
- Chapter 3, Initial Configuration
- Chapter 4, Configuring Interfaces
- Chapter 5, Configuring POS
- Chapter 6, Configuring Bridges
- Chapter 7, Configuring STP and RSTP
- Chapter 8, Configuring VLANs
- Chapter 9, Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling
- Chapter 10, Configuring Link Aggregation
- Chapter 11, Configuring Networking Protocols
- Chapter 12, Configuring IRB
- Chapter 13, Configuring VRF Lite
- Chapter 14, Configuring Quality of Service
- Chapter 15, Configuring the Switching Database Manager
- Chapter 16, Configuring Access Control Lists
- Chapter 17, Configuring Resilient Packet Ring
- Chapter 18, Configuring Ethernet over MLPS
- Chapter 19, POS on ONS Ethernet Cards
- Chapter 20, E-Series and G-Series Ethernet Operation
- Chapter 21, CE-100T-8 Ethernet Operation
- Chapter 22, Configuring RMON
- Chapter 23, Configuring SNMP
- Appendix A, Command Reference
- Appendix B, Unsupported CLI Commands
- Appendix C, Using Technical Support
- Basic IP Routing Protocol Configuration
- Configuring IP Routing
- Configuring Static Routes
- Monitoring Static Routes
- Monitoring and Maintaining the IP Network
- Understanding IP Multicast Routing
Configuring Networking Protocols
This chapter describes how to configure the ML-Series card for supported IP routing protocols. It is intended to provide enough information for a network administrator to get the protocols up and running. However, this section does not provide in-depth configuration detail for each protocol. For detailed information, refer to the Cisco IOS IP and IP Routing Configuration Guide and the Cisco IOS IP and IP Routing Command Reference publications.
This chapter contains the following major sections:
•
Basic IP Routing Protocol Configuration
•Monitoring and Maintaining the IP Network
•Understanding IP Multicast Routing
•Configuring IP Multicast Routing
•Monitoring and Verifying IP Multicast Operation
Basic IP Routing Protocol Configuration
IP routing is enabled by default on the ML-Series card.
For IP routing, you need the following to configure your interface:
•IP address
•IP subnet mask
You also need to do the following:
•Select a routing protocol.
•Assign IP network numbers to be advertised.
The ML Series supports the routing protocols listed and described in the following sections.
To configure IP routing protocols to run on a Fast Ethernet, Gigabit Ethernet, or Packet-over-SONET/SDH (POS) interface, perform one of the following procedures, depending on the protocol you are configuring.
RIP
To configure the Routing Information Protocol (RIP), perform the following procedure, beginning in global configuration mode:
EIGRP
To configure the Enhanced Interior Gateway Routing Protocol (EIGRP), perform the following procedure, beginning in global configuration mode:
OSPF
To configure the Open Shortest Path First (OSPF) protocol, perform the following procedure, beginning in global configuration mode:
BGP
To configure the Border Gateway Protocol (BGP), perform the following procedure, beginning in global configuration mode:
Enabling IP Routing
Beginning in privileged EXEC mode, follow this procedure to enable IP routing:
Note By default, IP routing is already enabled.
Use the no ip routing global configuration command (Example 11-1) to disable routing.
Example 11-1 Enabling IP Routing Using RIP as the Routing Protocol
Router# configure terminal
Router(config)# ip routing
Router(config)# router rip
Router(config-router)# network 10.0.0.0
Router(config-router)# end
Configuring IP Routing
You can now set up parameters for the selected routing protocols as described in these sections:
Configuring RIP
The Routing Information Protocol (RIP) is an Interior Gateway Protocol (IGP) created for use in small, homogeneous networks. It is a distance-vector routing protocol that uses broadcast User Datagram Protocol (UDP) data packets to exchange routing information. The protocol is documented in RFC 1058. You can find detailed information about RIP in IP Routing Fundamentals, published by Cisco Press.
Using RIP, the switch sends routing information updates (advertisements) every 30 seconds. If a router does not receive an update from another router for 180 seconds or more, it marks the routes served by that router as unusable. If there is still no update after 240 seconds, the router removes all routing table entries for the nonupdating router.
RIP uses hop counts to rate the value of different routes. The hop count is the number of routers that can be traversed in a route. A directly connected network has a hop count of zero; a network with a hop count of 16 is unreachable. This small range (0 to 15) makes RIP unsuitable for large networks.
If the router has a default network path, RIP advertises a route that links the router to the pseudo network 0.0.0.0. The 0.0.0.0 network does not exist; it is treated by RIP as a network to implement the default routing feature. The switch advertises the default network if a default was learned by RIP or if the router has a gateway of last resort and RIP is configured with a default metric. RIP sends updates to the interfaces in specified networks. If an interface's network is not specified, it is not advertised in any RIP update.
Table 11-1 shows the default RIP configuration.
To configure RIP, enable RIP routing for a network and optionally configure other parameters.
Beginning in privileged EXEC mode, follow this procedure to enable and configure RIP:
To turn off the RIP routing process, use the no router rip global configuration command.
To display the parameters and current state of the active routing protocol process, use the show ip protocols privileged EXEC command (Example 11-2).
Example 11-2 show ip protocols Command Output (Showing RIP Processes)
Router# show ip protocols
Routing Protocol is "rip"
Sending updates every 30 seconds, next due in 15 seconds
Invalid after 180 seconds, hold down 180, flushed after 240
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
Redistributing: rip
Default version control: send version 1, receive any version
Interface Send Recv Triggered RIP Key-chain
FastEthernet0 1 1 2
POS0 1 1 2
Automatic network summarization is in effect
Maximum path: 4
Routing for Networks:
192.168.2.0
192.168.3.0
Routing Information Sources:
Gateway Distance Last Update
192.168.2.1 120 00:00:23
Distance: (default is 120)
Use the show ip rip database privileged EXEC command to display summary address entries in the RIP database (Example 11-3).
Example 11-3 show ip rip database Command Output
Router# show ip rip database
192.168.1.0/24 auto-summary
192.168.1.0/24
[1] via 192.168.2.1, 00:00:24, POS0
192.168.2.0/24 auto-summary
192.168.2.0/24 directly connected, POS0
192.168.3.0/24 auto-summary
192.168.3.0/24 directly connected, FastEthernet0
RIP Authentication
RIP Version 1 does not support authentication. If you are sending and receiving RIP Version 2 packets, you can enable RIP authentication on an interface. The key chain determines the set of keys that can be used on the interface. If a key chain is not configured, no authentication is performed, not even the default.
The switch supports two modes of authentication on interfaces for which RIP authentication is enabled: plain text and message-digest key (MD5). The default is plain text.
Beginning in privileged EXEC mode, follow this procedure to configure RIP authentication on an interface:
To restore clear text authentication, use the no ip rip authentication mode interface configuration command. To prevent authentication, use the no ip rip authentication key-chain interface configuration command.
Summary Addresses and Split Horizon
Routers connected to broadcast-type IP networks and using distance-vector routing protocols normally use the split-horizon mechanism to reduce the possibility of routing loops. Split horizon blocks information about routes from being advertised by a router on any interface from which that information originated. This feature usually optimizes communication among multiple routers, especially when links are broken.
Note In general, disabling split horizon is not recommended unless you are certain that your application requires it to properly advertise routes.
If you want to configure an interface running RIP to advertise a summarized local IP address pool on a network access server for dial-up clients, use the ip summary-address rip interface configuration command.
Beginning in privileged EXEC mode, follow these steps to set an interface to advertise a summarized local IP address pool and to disable split horizon on the interface:
To disable IP summarization, use the no ip summary-address rip router configuration command.
Note If split horizon is enabled, neither autosummary nor interface summary addresses (those configured with the ip summary-address rip router configuration command) are advertised.
Configuring OSPF
This section briefly describes how to configure the Open Shortest Path First (OSPF) protocol. For a complete description of the OSPF commands, refer to the "OSPF Commands" chapter of the Cisco IOS IP and IP Routing Command Reference publication.
OSPF is an IGP designed expressly for IP networks, supporting IP subnetting and tagging of externally derived routing information. OSPF also allows packet authentication and uses IP multicast when sending and receiving packets. The Cisco implementation supports RFC 1253, the OSPF MIB.
The Cisco implementation conforms to the OSPF Version 2 specifications with these key features:
•Stub areas—Definition of stub areas is supported.
•Route redistribution—Routes learned through any IP routing protocol can be redistributed into another IP routing protocol. At the intradomain level, this means that OSPF can import and export routes learned through protocols such as EIGRP and RIP.
•Authentication—Plain text and MD5 authentication among neighboring routers within an area are supported.
•Routing interface parameter—Configurable parameters supported include interface output cost, retransmission interval, interface transmit delay, router priority, router dead and hello intervals, and authentication key.
•Virtual links—Virtual links are supported.
•Not-so-stubby-area (NSSA)—RFC 1587.
OSPF typically requires coordination among many internal routers, area border routers (ABRs) connected to multiple areas, and autonomous system boundary routers (ASBRs). The minimum configuration would use all default parameter values, no authentication, and interfaces assigned to areas. If you customize your environment, you must ensure coordinated configuration of all routers.
Table 11-2 shows the default OSPF configuration.
Figure 11-1 shows an example of an IP routing protocol using OSPF.
Figure 11-1 IP Routing Protocol Example Using OSPF
Enabling OSPF requires that you create an OSPF routing process, specify the range of IP addresses to be associated with the routing process, and assign area IDs to be associated with that range.
Beginning in privileged EXEC mode, follow this procedure to enable OSPF:
To terminate an OSPF routing process, use the no router ospf process-id global configuration command.
Example 11-4 shows an example of configuring an OSPF routing process. In the example, a process number of 1 is assigned. Example 11-5 shows the output of the command used to verify the OSPF process ID.
Example 11-4 Configuring an OSPF Routing Process
Router(config)# router ospf 1
Router(config-router)# network 192.168.1.0 0.0.0.255 area 0
Example 11-5 show ip protocols Privileged EXEC Command Output
Router# show ip protocols
Routing Protocol is "ospf 1"
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
Router ID 192.168.3.1
Number of areas in this router is 1. 1 normal 0 stub 0 nssa
Maximum path: 4
Routing for Networks:
192.168.2.0 0.0.0.255 area 0
192.168.3.0 0.0.0.255 area 0
Routing Information Sources:
Gateway Distance Last Update
192.168.3.1 110 00:03:34
192.168.2.1 110 00:03:34
Distance: (default is 110)
OSPF Interface Parameters
You can use the ip ospf interface configuration commands to modify interface-specific OSPF parameters. You are not required to modify any of these parameters, but some interface parameters (hello interval, dead interval, and authentication key) must be consistent across all routers in an attached network. If you modify these parameters, be sure all routers in the network have compatible values.
Note The ip ospf interface configuration commands are all optional.
Beginning in privileged EXEC mode, follow these steps to modify OSPF interface parameters:
Use the no form of these commands to remove the configured parameter value or return to the default value. Example 11-6 shows the output of the show ip ospf interface privileged EXEC command.
Example 11-6 show ip ospf interface Privileged EXEC Command Output
Router# show ip ospf interface
FastEthernet0 is up, line protocol is up
Internet Address 192.168.3.1/24, Area 0
Process ID 1, Router ID 192.168.3.1, Network Type BROADCAST, Cost: 1
Transmit Delay is 1 sec, State DR, Priority 1
Designated Router (ID) 192.168.3.1, Interface address 192.168.3.1
No backup designated router on this network
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 00:00:01
Index 2/2, flood queue length 0
Next 0x0(0)/0x0(0)
Last flood scan length is 0, maximum is 0
Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 0, Adjacent neighbor count is 0
Suppress hello for 0 neighbor(s)
POS0 is up, line protocol is up
Internet Address 192.168.2.2/24, Area 0
Process ID 1, Router ID 192.168.3.1, Network Type BROADCAST, Cost: 1
Transmit Delay is 1 sec, State DR, Priority 1
Designated Router (ID) 192.168.3.1, Interface address 192.168.2.2
Backup Designated router (ID) 192.168.2.1, Interface address 192.168.2.1
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 00:00:05
Index 1/1, flood queue length 0
Next 0x0(0)/0x0(0)
Last flood scan length is 2, maximum is 2
Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 1, Adjacent neighbor count is 1
Adjacent with neighbor 192.168.2.1 (Backup Designated Router)
Suppress hello for 0 neighbor(s)
OSPF Area Parameters
You can optionally configure several OSPF area parameters. These parameters include authentication for password-based protection against unauthorized access to an area, stub areas, and NSSAs. Stub areas are areas into which information about external routes is not sent. Instead, the ABR generates a default external route into the stub area for destinations outside the autonomous system (AS). An NSSA does not flood all LSAs from the core into the area, but can import AS external routes within the area by redistribution.
Route summarization is the consolidation of advertised addresses into a single summary route to be advertised by other areas. If network numbers are contiguous, you can use the area range router configuration command to configure the ABR to advertise a summary route that covers all networks in the range.
Note The OSPF area router configuration commands are all optional.
Beginning in privileged EXEC mode, follow these steps to configure area parameters:
Use the no form of these commands to remove the configured parameter value or to return to the default value. Example 11-7 shows the output of the show ip ospf database and the show ip ospf privileged EXEC commands.
Example 11-7 show ip ospf database and show ip ospf Privileged EXEC Command Ouputs
Router# show ip ospf database
OSPF Router with ID (192.168.3.1) (Process ID 1)
Router Link States (Area 0)
Link ID ADV Router Age Seq# Checksum Link count
192.168.2.1 192.168.2.1 428 0x80000003 0x004AB8 2
192.168.3.1 192.168.3.1 428 0x80000003 0x006499 2
Net Link States (Area 0)
Link ID ADV Router Age Seq# Checksum
192.168.2.2 192.168.3.1 428 0x80000001 0x00A4E0
Router# show ip ospf
Routing Process "ospf 1" with ID 192.168.3.1
Supports only single TOS(TOS0) routes
Supports opaque LSA
SPF schedule delay 5 secs, Hold time between two SPFs 10 secs
Minimum LSA interval 5 secs. Minimum LSA arrival 1 secs
Number of external LSA 0. Checksum Sum 0x000000
Number of opaque AS LSA 0. Checksum Sum 0x000000
Number of DCbitless external and opaque AS LSA 0
Number of DoNotAge external and opaque AS LSA 0
Number of areas in this router is 1. 1 normal 0 stub 0 nssa
External flood list length 0
Area BACKBONE(0)
Number of interfaces in this area is 2
Area has no authentication
SPF algorithm executed 4 times
Area ranges are
Number of LSA 3. Checksum Sum 0x015431
Number of opaque link LSA 0. Checksum Sum 0x000000
Number of DCbitless LSA 0
Number of indication LSA 0
Number of DoNotAge LSA 0
Flood list length 0
Other OSPF Behavior Parameters
You can optionally configure other OSPF parameters in router configuration mode:
•Route summarization—When redistributing routes from other protocols, each route is advertised individually in an external LSA. To help decrease the size of the OSPF link state database, you can use the summary-address router configuration command to advertise a single router for all the redistributed routes included in a specified network address and mask.
•Virtual links—In OSPF, all areas must be connected to a backbone area. You can establish a virtual link in case of a backbone-continuity break by configuring two ABRs as endpoints of a virtual link. Configuration information includes the identity of the other virtual endpoint (the other ABR) and the nonbackbone link that the two routers have in common (the transit area). Virtual links cannot be configured through a stub area.
•Default route—When you specifically configure redistribution of routes into an OSPF routing domain, the route automatically becomes an ASBR. You can force the ASBR to generate a default route into the OSPF routing domain.
•Domain Name Server (DNS) names for use in all OSPF show privileged EXEC command displays make it easier to identify a router than displaying it by router ID or neighbor ID.
•Default metrics—OSPF calculates the OSPF metric for an interface according to the bandwidth of the interface. The metric is calculated as ref-bw divided by bandwidth, where ref is 10 by default, and bandwidth (bw) is determined by the bandwidth interface configuration command. For multiple links with high bandwidth, you can specify a larger number to differentiate the cost on those links.
•Administrative distance—This is a rating of the trustworthiness of a routing information source, an integer between 0 and 255, with a higher value meaning a lower trust rating. An administrative distance of 255 means that the routing information source cannot be trusted at all and should be ignored. OSPF uses three different administrative distances: routes within an area (intra-area), routes to another area (interarea), and routes from another routing domain learned through redistribution (external). You can change any of the distance values.
•Passive interfaces—Because interfaces between two devices on an Ethernet represent only one network segment, to prevent OSPF from sending hello packets for the sending interface, you must configure the sending device to be a passive interface. Both devices can identify each other through the hello packet for the receiving interface.
•Route calculation timers—You can configure the delay time between when OSPF receives a topology change and when it starts the shortest path first (SPF) calculation. You can also configure the hold time between two SPF calculations.
•Log neighbor changes—You can configure the router to send a syslog message when an OSPF neighbor state changes, providing a high-level view of changes in the router.
Beginning in privileged EXEC mode, follow this procedure to configure these OSPF parameters:
|
|
|
|
|---|---|---|
Step 1 |
Router# configure terminal |
Enters global configuration mode. |
Step 2 |
Router(config)# router ospf process-id
|
Enables OSPF routing, and enters router configuration mode. |
Step 3 |
Router(config)# summary-address
address-mask
|
(Optional) Specifies an address and IP subnet mask for redistributed routes so that only one summary route is advertised. |
Step 4 |
Router(config)# area area-id virtual-link router-id [hello-interval seconds] [retransmit-interval seconds] [trans] {[authentication-key key] | [message-digest-key key-id md5 key]} |
(Optional) Establishes a virtual link and set its parameters. See the "OSPF Interface Parameters" section for parameter definitions and Table 11-2 for virtual link defaults. |
Step 5 |
Router(config)# default-information originate [always] [metric metric-value] [metric-type type-value] [route-map map-name] |
(Optional) Forces the ASBR to generate a default route into the OSPF routing domain. Parameters are all optional. |
Step 6 |
Router(config)# ip ospf name-lookup |
(Optional) Configures DNS name lookup. The default is disabled. |
Step 7 |
Router(config)# ip auto-cost
reference-bandwidth ref-bw
|
(Optional) Specifies an address range for which a single route will be advertised. Use this command only with area border routers. |
Step 8 |
Router(config)# distance ospf
{[inter-area dist1] | [inter-area
dist2] | [external dist3]}
|
(Optional) Changes the OSPF distance values. The default distance for each type of route is 110. The range is 1 to 255. |
Step 9 |
Router(config)# passive-interface type number |
(Optional) Suppresses the sending of hello packets through the specified interface. |
Step 10 |
Router(config)# timers spf spf-delay
spf-holdtime
|
(Optional) Configures route calculation timers. • • |
Step 11 |
Router(config)# ospf log-adj-changes |
(Optional) Sends syslog message when a neighbor state changes. |
Step 12 |
Router(config)# end |
Returns to privileged EXEC mode. |
Step 13 |
Router# show ip ospf [process-id [area-id]] database |
Displays lists of information related to the OSPF database for a specific router. For some of the keyword options, see to the "Monitoring OSPF" section. |
Step 14 |
Router# copy running-config startup-config |
(Optional) Saves your entries in the configuration file. |
Change LSA Group Pacing
The OSPF LSA group pacing feature allows the router to group OSPF LSAs and pace the refreshing, check-summing, and aging functions for more efficient router use. This feature is enabled by default with a four-minute default pacing interval, and you do not usually need to modify this parameter. The optimum group pacing interval is inversely proportional to the number of LSAs the router is refreshing, check-summing, and aging. For example, if you have approximately 10,000 LSAs in the database, decreasing the pacing interval would benefit you. If you have a very small database (40 to 100 LSAs), increasing the pacing interval to 10 to 20 minutes might benefit you slightly.
Beginning in privileged EXEC mode, follow this procedure to configure OSPF LSA pacing:
To return to the default value, use the no timers lsa-group-pacing router configuration command.
Loopback Interface
OSPF uses the highest IP address configured on the interfaces as its router ID. If this interface is down or removed, the OSPF process must recalculate a new router ID and resend all its routing information out of its interfaces. If a loopback interface is configured with an IP address, OSPF uses this IP address as its router ID, even if other interfaces have higher IP addresses. Because loopback interfaces never fail, this provides greater stability. OSPF automatically prefers a loopback interface over other interfaces, and it chooses the highest IP address among all loopback interfaces.
Beginning in privileged EXEC mode, follow this procedure to configure a loopback interface:
Use the no interface loopback 0 global configuration command to disable the loopback interface.
Monitoring OSPF
You can display specific statistics such as the contents of IP routing tables, caches, and databases.
Table 11-3 lists some of the privileged EXEC commands for displaying statistics. For more show ip ospf database privileged EXEC command options and for explanations of fields in the resulting display, refer to the Cisco IOS IP and IP Routing Command Reference.
Configuring EIGRP
Enhanced IGRP (EIGRP) is a Cisco proprietary enhanced version of the Interior Gateway Routing Protocol (IGRP). Enhanced IGRP uses the same distance vector algorithm and distance information as IGRP; however, the convergence properties and the operating efficiency of Enhanced IGRP are significantly improved.
The convergence technology employs an algorithm referred to as the Diffusing Update Algorithm (DUAL), which guarantees loop-free operation at every instant throughout a route computation and allows all devices involved in a topology change to synchronize at the same time. Routers that are not affected by topology changes are not involved in recomputations.
IP EIGRP provides increased network width. With RIP, the largest possible width of your network is 15 hops. When IGRP is enabled, the largest possible width is 224 hops. Because the EIGRP metric is large enough to support thousands of hops, the only barrier to expanding the network is the transport-layer hop counter. EIGRP increments the transport control field only when an IP packet has traversed 15 routers and the next hop to the destination was learned through EIGRP. When a RIP route is used as the next hop to the destination, the transport control field is incremented as usual.
EIGRP offers the following features:
•Fast convergence
•Incremental updates when the state of a destination changes, instead of sending the entire contents of the routing table, minimizing the bandwidth required for EIGRP packets
•Less CPU usage than IGRP because full update packets do not need to be processed each time they are received
•Protocol-independent neighbor discovery mechanism to learn about neighboring routers
•Variable-length subnet masks (VLSMs)
•Arbitrary route summarization
•EIGRP scales to large networks
EIGRP has four basic components:
•Neighbor discovery and recovery is the process that routers use to dynamically learn of other routers on their directly attached networks. Routers must also discover when their neighbors become unreachable or inoperative. Neighbor discovery and recovery is achieved with low overhead by periodically sending small hello packets. As long as hello packets are received, the Cisco IOS software can determine that a neighbor is alive and functioning. When this status is determined, the neighboring routers can exchange routing information.
•The reliable transport protocol is responsible for guaranteed, ordered delivery of EIGRP packets to all neighbors. It supports intermixed transmission of multicast and unicast packets. Some EIGRP packets must be sent reliably, and others need not be. For efficiency, reliability is provided only when necessary. For example, on a multiaccess network that has multicast capabilities (such as Ethernet), it is not necessary to send hellos reliably to all neighbors individually. Therefore, EIGRP sends a single multicast hello with an indication in the packet informing the receivers that the packet need not be acknowledged. Other types of packets (such as updates) require acknowledgment, which is shown in the packet. The reliable transport has a provision to send multicast packets quickly when there are unacknowledged packets pending. Doing so helps ensure that convergence time remains low in the presence of varying speed links.
•The DUAL finite state machine embodies the decision process for all route computations. It tracks all routes advertised by all neighbors. DUAL uses the distance information (known as a metric) to select efficient, loop-free paths. DUAL selects routes to be inserted into a routing table based on feasible successors. A successor is a neighboring router used for packet forwarding that has a least-cost path to a destination that is guaranteed not to be part of a routing loop. When there are no feasible successors, but there are neighbors advertising the destination, a recomputation must occur. This is the process whereby a new successor is determined. The amount of time it takes to recompute the route affects the convergence time. Recomputation is processor-intensive; it is advantageous to avoid recomputation if it is not necessary. When a topology change occurs, DUAL tests for feasible successors. If there are feasible successors, it uses any it finds to avoid unnecessary recomputation.
•The protocol-dependent modules are responsible for network layer protocol-specific tasks. An example is the IP EIGRP module, which is responsible for sending and receiving EIGRP packets that are encapsulated in IP. It is also responsible for parsing EIGRP packets and informing DUAL of the new information received. EIGRP asks DUAL to make routing decisions, but the results are stored in the IP routing table. EIGRP is also responsible for redistributing routes learned by other IP routing protocols.
Table 11-4 shows the default EIGRP configuration.
To create an EIGRP routing process, you must enable EIGRP and associate networks. EIGRP sends updates to the interfaces in the specified networks. If you do not specify an interface network, it is not advertised in any EIGRP update.
EIGRP Router Mode Commands
Beginning in privileged EXEC mode, follow these steps to configure EIGRP. Configuring the routing process is required; other steps are optional.
Use the no forms of these commands to disable the feature or return the setting to the default value. Example 11-8 shows the output for the show ip protocols privileged EXEC command.
Example 11-8 show ip protocols privileged EXEC Command Output (for EIGRP)
Router# show ip protocols
Routing Protocol is "eigrp 1"
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
Default networks flagged in outgoing updates
Default networks accepted from incoming updates
EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0
EIGRP maximum hopcount 100
EIGRP maximum metric variance 1
Redistributing: eigrp 1
Automatic network summarization is in effect
Automatic address summarization:
192.168.3.0/24 for POS0
192.168.2.0/24 for FastEthernet0
Maximum path: 4
Routing for Networks:
192.168.2.0
192.168.3.0
Routing Information Sources:
Gateway Distance Last Update
192.168.2.1 90 00:03:16
Distance: internal 90 external 170
EIGRP Interface Mode Commands
Other optional EIGRP parameters can be configured on an interface basis.
Beginning in privileged EXEC mode, follow these steps:
Use the no forms of these commands to disable the feature or return the setting to the default value. Example 11-9 shows the output of the show ip eigrp interface privileged EXEC command.
Example 11-9 show ip eigrp interface Privileged EXEC Command Output
Router# show ip eigrp interface
IP-EIGRP interfaces for process 1
Xmit Queue Mean Pacing Time Multicast Pending
Interface Peers Un/Reliable SRTT Un/Reliable Flow Timer Routes
PO0 1 0/0 20 0/10 50 0
Fa0 0 0/0 0 0/10 0 0
Configure EIGRP Route Authentication
EIGRP route authentication provides MD5 authentication of routing updates from the EIGRP routing protocol to prevent the introduction of unauthorized or false routing messages from unapproved sources.
Beginning in privileged EXEC mode, follow these steps to enable authentication:
Use the no forms of these commands to disable the feature or to return the setting to the default value.
Monitoring and Maintaining EIGRP
You can delete neighbors from the neighbor table. You can also display various EIGRP routing statistics. Table 11-5 lists the privileged EXEC commands for deleting neighbors and displaying statistics. For explanations of fields in the resulting display, refer to the Cisco IOS IP and IP Routing Command Reference publication.
Example 11-10 shows the output of the show ip eigrp interface privileged EXEC command. Example 11-11 shows the output of the show ip eigrp neighbors privileged EXEC command. Example 11-12 shows the output of the show ip eigrp topology privileged EXEC command. Example 11-13 shows the output of the show ip eigrp traffic privileged EXEC command.
Example 11-10 show ip eigrp interface Privileged EXEC Command Output
Router# show ip eigrp interface
IP-EIGRP interfaces for process 1
Xmit Queue Mean Pacing Time Multicast Pending
Interface Peers Un/Reliable SRTT Un/Reliable Flow Timer Routes
PO0 1 0/0 20 0/10 50 0
Fa0 0 0/0 0 0/10 0 0
Example 11-11 show ip eigrp neighbors Privileged EXEC Command Output
Router# show ip eigrp neighbors
IP-EIGRP neighbors for process 1
H Address Interface Hold Uptime SRTT RTO Q Seq Type
(sec) (ms) Cnt Num
0 192.168.2.1 PO0 13 00:08:15 20 200 0 2
Example 11-12 show ip eigrp topology Privileged EXEC Command Output
Router# show ip eigrp topology
IP-EIGRP Topology Table for AS(1)/ID(192.168.3.1)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status
P 192.168.1.0/24, 1 successors, FD is 30720
via 192.168.2.1 (30720/28160), POS0
P 192.168.2.0/24, 1 successors, FD is 10752
via Connected, POS0
P 192.168.3.0/24, 1 successors, FD is 28160
via Connected, FastEthernet0
Example 11-13 show ip eigrp traffic Privileged EXEC Command Output
Router# show ip eigrp traffic
IP-EIGRP Traffic Statistics for process 1
Hellos sent/received: 273/136
Updates sent/received: 5/2
Queries sent/received: 0/0
Replies sent/received: 0/0
Acks sent/received: 1/2
Input queue high water mark 1, 0 drops
SIA-Queries sent/received: 0/0
SIA-Replies sent/received: 0/0
Border Gateway Protocol and Classless Interdomain Routing
Border Gateway Protocol (BGP) is an Exterior Gateway Protocol (EGP) that allows you to set up an interdomain routing system to automatically guarantee the loop-free exchange of routing information between autonomous systems. In BGP, each route consists of a network number, a list of autonomous systems that information has passed through (called the autonomous system path), and a list of other path attributes.
Layer 3 switching supports BGP version 4, including CIDR. CIDR lets you reduce the size of your routing tables by creating aggregate routes resulting in supernets. CIDR eliminates the concept of network classes within BGP and supports the advertising of IP prefixes. CIDR routes can be carried by OSPF, EIGRP, and RIP.
Configuring BGP
To configure BGP routing, perform the following steps, beginning in global configuration mode:
Example 11-14 shows and example of configuring BGP routing.
Example 11-14 Configuring BGP Routing
Router(config)# ip routing
Router(config)# router bgp 30
Router(config-router)# network 192.168.1.1
Router(config-router)# neighbor 192.168.2.1
Router(config-router)# end
For more information about configuring BGP routing, refer to the "Configuring BGP" chapter in the Cisco IOS IP and IP Routing Configuration Guide.
Verifying the BGP Configuration
Table 11-6 lists some common EXEC commands used to view the BGP configuration. Example 11-15 shows the output of the commands listed in Table 11-6.
Example 11-15 BGP Configuration Information
Router# show ip protocols
Routing Protocol is "bgp 1"
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
IGP synchronization is enabled
Automatic route summarization is enabled
Redistributing: connected
Neighbor(s):
Address FiltIn FiltOut DistIn DistOut Weight RouteMap
192.168.2.1
Maximum path: 1
Routing for Networks:
Routing Information Sources:
Gateway Distance Last Update
Distance: external 20 internal 200 local 200
Router# show ip bgp neighbor
BGP neighbor is 192.168.2.1, remote AS 1, internal link
BGP version 4, remote router ID 192.168.2.1
BGP state = Established, up for 00:08:46
Last read 00:00:45, hold time is 180, keepalive interval is 60 seconds
Neighbor capabilities:
Route refresh: advertised and received(new)
Address family IPv4 Unicast: advertised and received
Received 13 messages, 0 notifications, 0 in queue
Sent 13 messages, 0 notifications, 0 in queue
Route refresh request: received 0, sent 0
Default minimum time between advertisement runs is 5 seconds
For address family: IPv4 Unicast
BGP table version 3, neighbor version 3
Index 1, Offset 0, Mask 0x2
2 accepted prefixes consume 72 bytes
Prefix advertised 2, suppressed 0, withdrawn 0
Number of NLRIs in the update sent: max 2, min 0
Connections established 1; dropped 0
Last reset never
Connection state is ESTAB, I/O status: 1, unread input bytes: 0
Local host: 192.168.2.2, Local port: 179
Foreign host: 192.168.2.1, Foreign port: 11001
Enqueued packets for retransmit: 0, input: 0 mis-ordered: 0 (0 bytes)
Event Timers (current time is 0x45B7B4):
Timer Starts Wakeups Next
Retrans 13 0 0x0
TimeWait 0 0 0x0
AckHold 13 9 0x0
SendWnd 0 0 0x0
KeepAlive 0 0 0x0
GiveUp 0 0 0x0
PmtuAger 0 0 0x0
DeadWait 0 0 0x0
iss: 3654396253 snduna: 3654396567 sndnxt: 3654396567 sndwnd: 16071
irs: 3037331955 rcvnxt: 3037332269 rcvwnd: 16071 delrcvwnd: 313
SRTT: 247 ms, RTTO: 663 ms, RTV: 416 ms, KRTT: 0 ms
minRTT: 4 ms, maxRTT: 300 ms, ACK hold: 200 ms
Flags: passive open, nagle, gen tcbs
Datagrams (max data segment is 1460 bytes):
Rcvd: 15 (out of order: 0), with data: 13, total data bytes: 313
Sent: 22 (retransmit: 0), with data: 12, total data bytes: 313
Router# show ip bgp summary
BGP router identifier 192.168.3.1, local AS number 1
BGP table version is 3, main routing table version 3
3 network entries and 4 paths using 435 bytes of memory
2 BGP path attribute entries using 120 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP activity 3/6 prefixes, 4/0 paths, scan interval 60 secs
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
192.168.2.1 4 1 14 14 3 0 0 00:09:45 2
Router# show ip bgp
BGP table version is 3, local router ID is 192.168.3.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
* i192.168.1.0 192.168.2.1 0 100 0 ?
* i192.168.2.0 192.168.2.1 0 100 0 ?
*> 0.0.0.0 0 32768 ?
*> 192.168.3.0 0.0.0.0 0 32768 ?
Configuring IS-IS
To configure Intermediate System-to-Intermediate System (IS-IS) routing, perform the following steps, beginning in global configuration mode:
Example 11-16 shows an example of IS-IS routing configuration.
Example 11-16 Configuring IS-IS Routing
Router(config)# router isis
Router(config-router)# net 49.0001.0000.0000.000a.00
Router(config-router)# interface gigabitethernet 0
Router(config-if)# ip router isis
Router(config-if)# end
For more information about configuring IS-IS routing, refer to the "Configuring Integrated IS-IS" chapter in the Cisco IOS IP and IP Routing Configuration Guide.
Verifying the IS-IS Configuration
To verify the IS-IS configuration, use the EXEC commands listed in Table 11-7. Example 11-17 shows examples of the commands in Table 11-7 and their output.
Note The ML Series does not support Connectionless Network Service Protocol (CLNS) routing.
Example 11-17 IS-IS Configuration
Router# show ip protocols
Routing Protocol is "isis"
Invalid after 0 seconds, hold down 0, flushed after 0
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
Redistributing: isis
Address Summarization:
None
Maximum path: 4
Routing for Networks:
FastEthernet0
POS0
Routing Information Sources:
Gateway Distance Last Update
192.168.2.1 115 00:06:48
Distance: (default is 115)
Router# show isis database
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL
Router_A.00-00 0x00000003 0xA72F 581 0/0/0
Router_A.02-00 0x00000001 0xA293 581 0/0/0
Router.00-00 * 0x00000004 0x79F9 582 0/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL
Router_A.00-00 0x00000004 0xF0D6 589 0/0/0
Router_A.02-00 0x00000001 0x328C 581 0/0/0
Router.00-00 * 0x00000004 0x6A09 586 0/0/0
Router# show clns neighbors
System Id Interface SNPA State Holdtime Type Protocol
Router_A PO0 0005.9a39.6790 Up 7 L1L2 IS-IS
Configuring Static Routes
Static routes are user-defined routes that cause packets moving between a source and a destination to take a specified path. Static routes can be important if the router cannot build a route to a particular destination. They are also useful for specifying a gateway of last resort to which all unroutable packets are sent.
Beginning in privileged EXEC mode, follow these steps to configure a static route:
|
|
|
|
|---|---|---|
Step 1 |
Router# configure terminal |
Enters global configuration mode. |
Step 2 |
Router(config)# ip route prefix mask
{ address | interface } [distance]
|
Establishes a static route. Illustrated in Example 11-18. |
Step 3 |
Router(config)# end |
Returns to privileged EXEC mode. |
Step 4 |
Router# copy running-config startup-config |
(Optional) Saves your entries in the configuration file. |
Example 11-18 Static Route
Router(config)# ip route 0.0.0.0 0.0.0.0 192.168.2.1
Use the no ip route prefix mask {address | interface} global configuration command to remove a static route. Use the show ip route privileged EXEC command to view information about the static IP route (Example 11-19).
Example 11-19 show ip route Privileged EXEC Command Output (with a Static Route Configured)
Router# show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is 192.168.2.1 to network 0.0.0.0
C 192.168.2.0/24 is directly connected, POS0
C 192.168.3.0/24 is directly connected, FastEthernet0
S* 0.0.0.0/0 [1/0] via 192.168.2.1
The output from the show ip route privileged EXEC command lists codes for the routing protocols. Table 11-8 shows the default administrative distances for these routing protocols.
Monitoring Static Routes
You can display statistics about static routes with the show ip route command (Example 11-20). For more show ip privileged EXEC command options and for explanations of fields in the resulting display, refer to the Cisco IOS IP and IP Routing Command Reference publication.
Example 11-20 show ip route Command Output (with a Static Route Configured)
Router# show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is 192.168.2.1 to network 0.0.0.0
C 192.168.2.0/24 is directly connected, POS0
C 192.168.3.0/24 is directly connected, FastEthernet0
S* 0.0.0.0/0 [1/0] via 192.168.2.1
Monitoring and Maintaining the IP Network
You can remove all contents of a particular cache, table, or database. You can also display specific statistics. Use the privileged EXEC commands in Table 11-9 to clear routes or display status.
Understanding IP Multicast Routing
As networks increase in size, multicast routing becomes critically important as a means to determine which segments require multicast traffic and which do not. IP multicasting allows IP traffic to be propagated from one source to a number of destinations, or from many sources to many destinations. Rather than sending one packet to each destination, one packet is sent to the multicast group identified by a single IP destination group address.
A principal component of IP multicasting is the Internet Group Management Protocol (IGMP). Hosts identify their multicast group membership by sending IGMP messages to the ML-Series card. Traffic is sent to all members of a multicast group. A host can be a member of more than one group at a time. In addition, a host does not need to be a member of a group to send data to that group. When you enable Protocol Independent Multicast (PIM) on an interface, you will have enabled IGMP operation on that same interface.
The ML-Series cards support the protocol independent multicast (PIM) routing protocol and the Auto-RP configuration.
PIM includes three different modes of behavior for dense and sparse traffic environments. These are referred to as dense mode, sparse mode, and sparse-dense mode.
PIM dense mode assumes that the downstream networks want to receive the datagrams forwarded to them. The ML-Series card forwards all packets on all outgoing interfaces until pruning and truncating occur. Interfaces that have PIM dense mode enabled receive the multicast data stream until it times out. PIM dense mode is most useful under these conditions:
•When senders and receivers are in close proximity to each other
•When the internetwork has fewer senders than receivers
•When the stream of multicast traffic is constant
PIM sparse mode assumes that the downstream networks do not want to forward multicast packets for a group unless there is an explicit request for the traffic. PIM sparse mode defines a rendezvous point, which is used as a registration point to facilitate the proper routing of packets.
When a sender wants to send data, it first sends the data to the rendezvous point. When a ML-Series card is ready to receive data, it registers with the rendezvous point. After the data stream begins to flow from the sender to the rendezvous point and then to the receiver, ML-Series cards in the data path optimize the path by automatically removing any unnecessary hops, including the rendezvous point.
PIM sparse mode is optimized for environments in which there are many multipoint data streams and each multicast stream goes to a relatively small number of LANs in the internetwork. PIM sparse mode is most useful under these conditions:
•When there are few receivers in the group
•When senders and receivers are separated by WAN links
•When the stream of multicast traffic is intermittent
Note The ML-Series card support Reverse Path Forwarding (RPF) multicast, but not RPF unicast.
Configuring IP Multicast Routing
To configure IP multicast routing, perform the following procedure, beginning in global configuration mode:
Monitoring and Verifying IP Multicast Operation
After IP multicast routing is configured, you can monitor and verify its operation by performing the commands listed in Table 11-10, from privileged EXEC mode.
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