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Cisco's implementation of the Internet Protocol (IP) suite provides all major services contained in the TCP/IP specifications.
Use the commands in this chapter to configure and monitor the IP routing protocols. For IP routing protocol configuration information and examples, refer to the "Configuring IP Routing Protocols" chapter of the Router Products Configuration Guide.
To create an aggregate entry in a BGP routing table, use the aggregate-address router configuration command. To disable this feature, use the no form of this command.
aggregate-address address mask [as-set] [summary-only] [suppress-map map-name]| address | Aggregate address. |
| mask | Aggregate mask. |
| as-set | (Optional) Generates autonomous system set path information. |
| summary-only | (Optional) Filters more specific routes from updates. |
| suppress-map map-name | (Optional) Name of route-map to suppress. |
Disabled
Router configuration
You can implement aggregate routing in BGP either by redistributing an aggregate route into BGP or by using this conditional aggregate routing feature.
Using the aggregate-address command with no arguments will create an aggregate entry in the BGP routing table if there are any more-specific routes available that fall in the specified range. The aggregate route will be advertised as coming from your autonomous system and has the atomic aggregate attribute set to show that information might be missing. (By default, the atomic aggregate attribute is set unless you specify the as-set keyword in the aggregate-address command.)
Using the as-set keyword creates an aggregate entry using the same rules that the command follows without this keyword, but the path advertised for this route will be an AS_SET consisting of all elements contained in all paths that are being summarized. Do not use this form of aggregate-address when aggregating many paths, because this route must be continually withdrawn and re-updated as autonomous system path reachability information for the summarized routes changes.
Using the summary-only keyword not only creates the aggregate route (for example, 193.*.*.*) but will also suppress advertisements of more specific routes to all neighbors. If you only want to suppress advertisements to certain neighbors, you may use the neighbor distribute-list command, with caution. If a more-specific route leaks out, all BGP speakers will prefer that route over the less- specific aggregate you are generating (using longest-match routing).
Using the suppress-map keyword creates the aggregate route but suppresses advertisement of specified route maps. You can use the match clauses of route maps to selectively suppress some more specific routes of the aggregate and leave others unsuppressed. IP access lists and AS path access lists match clauses are supported.
In the following example, an aggregate address is created. The path advertised for this route will be an AS_SET consisting of all elements contained in all paths that are being summarized.
router bgp 5aggregate-address 193.0.0.0 255.0.0.0 as-set
match as-path
match ip address
route-map
To enable authentication for an OSPF area, use the area authentication router configuration command. To remove an area's authentication specificationor a specified area from the router's configuration, use the no form of this command.
area area-id authentication| area-id | Identifier of the area for which authentication is to be enabled. The identifier can be specified as either a decimal value or an IP address. |
Type 0 authentication (no authentication)
Router configuration
Specifying authentication for an area sets the authentication to Type 1 (simple password) as specified in RFC 1247. If this command is not included in the configuration file, authentication of Type 0 (no authentication) is assumed.
The authentication type must be the same for all routers in an area. The authentication password for all OSPF routers on a network must be the same if they are to communicate with each other via OSPF. Use the ip ospf authentication-key interface configuration command to specify this password.
To remove the area's authentication specification, use the no form of this command with the authentication keyword. To remove the specified area from the router's configuration, use the command no area area-id (with no other keywords).
The following example mandates authentication for areas 0 and 36.0.0.0 of OSPF routing process 201. Authentication keys are also provided.
interface ethernet 0 ip address 131.119.251.201 255.255.255.0 ip ospf authentication-key adcdefgh ! interface ethernet 1 ip address 36.56.0.201 255.255.0.0 ip ospf authentication-key ijklmnop ! router ospf 201 network 36.0.0.0 0.255.255.255 area 36.0.0.0 network 131.119.0.0 0.0.255.255 area 0 area 36.0.0.0 authentication area 0 authentication
area default-cost
area stub
ip ospf authentication-key
To specify a cost for the default summary route sent into a stub area, use the area default-cost router configuration command. To remove the assigned default route cost, use the no form of this command.
area area-id default-cost cost| area-id | Identifier for the stub area. The identifier can be specified as either a decimal value or as an IP address. |
| cost | Cost for the default summary route used for a stub area. The acceptable value is a 24-bit number. |
Cost of 1
Router configuration
This command is used only on an area border router attached to a stub area.
There are two stub area router configuration commands: the stub and default-cost options of the area command. In all routers attached to the stub area, the area should be configured as a stub area using the stub option of the area command. Use the default-cost option only on an area border router attached to the stub area. The default-cost option provides the metric for the summary default route generated by the area border router into the stub area.
The following example assigns a default-cost of 20 to stub network 36.0.0.0:
interface ethernet 0 ip address 36.56.0.201 255.255.0.0 ! router ospf 201 network 36.0.0.0 0.255.255.255 area 36.0.0.0 area 36.0.0.0 stub area 36.0.0.0 default-cost 20
To consolidate and summarize routes at an area boundary, use the area range router configuration command. To disable this function, use the no form of this command.
area area-id range address mask| area-id | Identifier of the area about which routes are to be summarized. It can be specified as either a decimal value or as an IP address. |
| address | IP address. |
| mask | IP mask. |
Disabled
Router configuration
The area range command is used only with area border routers. It is used to consolidate or summarize routes for an area. The result is that a single summary route is advertised to other areas by the area border router. Routing information is condensed at area boundaries. External to the area, a single route is advertised for each address range. This is called route summarization.
Multiple area router configuration commands specifying the range option can be configured. Thus, OSPF can summarize addresses for many different sets of address ranges.
The following example specifies one summary route to be advertised by the area border router to other areas for all subnets on network 36.0.0.0 and for all hosts on network 192.42.110.0:
interface ethernet 0 ip address 192.42.110.201 255.255.255.0 ! interface ethernet 1 ip address 36.56.0.201 255.255.0.0 ! router ospf 201 network 36.0.0.0 0.255.255.255 area 36.0.0.0 network 192.42.110.0 0.0.0.255 area 0 area 36.0.0.0 range 36.0.0.0 255.0.0.0 area 0 range 192.42.110.0 255.255.255.0
To define an area as a stub area, use the area stub router configuration command. To disable this function, use the no form of this command.
area area-id stub [no-summary]| area-id | Identifier for the stub area. The identifier can be either a decimal value or an IP address. |
| no-summary | (Optional) Prevents an area border router (ABR) from sending summary link advertisements into the stub area. |
No stub area is defined.
Router configuration
You must configure the area stub command on all routers in the stub area. Use the area router configuration command with the default-cost option to specify the cost of a default internal router sent into a stub area by an area border router.
There are two stub area router configuration commands: the stub and default-cost options of the area router configuration command. In all routers attached to the stub area, the area should be configured as a stub area using the stub option of the area command. Use the default-cost option only on an area border router attached to the stub area. The default-cost option provides the metric for the summary default route generated by the area border router into the stub area.
To further reduce the number of link state advertisements (LSA) sent into a stub area, you can configure no-summary on the ABR to prevent it from sending summary LSAs (LSA type 3) into the stub area.
The following example assigns a default cost of 20 to stub network 36.0.0.0:
interface ethernet 0 ip address 36.56.0.201 255.255.0.0 ! router ospf 201 network 36.0.0.0 0.255.255.255 area 36.0.0.0 area 36.0.0.0 stub area 36.0.0.0 default-cost 20
area authentication
area default-cost
To define an OSPF virtual link, use the area virtual-link router configuration command with the optional parameters. To remove a virtual link, use the no form of this command.
area area-id virtual-link router-id [hello-interval seconds] [retransmit-interval seconds]| area-id | Area ID assigned to the transit area for the virtual link. This can be either a decimal value or a valid IP address. There is no default. |
| router-id | Router ID associated with the virtual link neighbor. The router ID appears in the show ip ospf display. It is internally derived by each router from the router's interface IP addresses. This value must be entered in the format of an IP address. There is no default. |
| hello-interval | (Optional) Time in seconds between the Hello packets that the router sends on an interface. |
| seconds | (Optional) Unsigned integer value to be advertised in the router's Hello packets. The value must be the same for all routers attached to a common network. The default is 10 seconds. |
| retransmit-interval | (Optional) Time in seconds between link state advertisement retransmissions for adjacencies belonging to the interface. |
| seconds | (Optional) Expected round-trip delay between any two routers on the attached network. The value must be greater than the expected round-trip delay. The default is 5 seconds. |
| transmit-delay | (Optional) Estimated time in seconds it takes to transmit a link state update packet on the interface. |
| seconds | (Optional) Integer value that must be greater than zero. Link state advertisements in the update packet have their age incremented by this amount before transmission. The default value is 1 second. |
| dead-interval | (Optional) Time in seconds that a router's Hello packets are not seen before its neighbors declare the router down. |
| seconds | (Optional) Unsigned integer value. The default is four times the Hello interval, or 40 seconds. As with the Hello interval, this value must be the same for all routers attached to a common network. |
| authentication-key | (Optional) Password to be used by neighboring routers. |
| password | (Optional) Any continuous string of characters that you can enter from the keyboard up to 8 bytes in length. This string acts as a key that will allow the authentication procedure to generate or verify the authentication field in the OSPF header. This key is inserted directly into the OSPF header when originating routing protocol packets. A separate password can be assigned to each network on a per-interface basis. All neighboring routers on the same network must have the same password to be able to route OSPF traffic. The password is encrypted in the configuration file if the service password-encryption command is enabled. There is no default value. |
area-id: No area ID is predefined.
router-id: No router ID is predefined.
hello-interval seconds: 10 seconds
retransmit-interval seconds: 10 seconds
transmit-delay seconds: 1 second
dead-interval seconds: 40 seconds
authentication-key password: No password is predefined.
Router configuration
In OSPF, all areas must be connected to a backbone area. If the connection to the backbone is lost, it can be repaired by establishing a virtual link.
The smaller the Hello interval, the faster topological changes will be detected, but more routing traffic will ensue.
The setting of the retransmit interval should be conservative, or needless retransmissions will result. The value should be larger for serial lines and virtual links.
The transmit delay value should take into account the transmission and propagation delays for the interface.
A router will use the specified authentication key only when authentication is enabled for the backbone with the area area-id authentication router configuration command.
Any keywords and arguments you specify after the authentication-key password keyword-argument pair are ignored. Therefore, specify any optional arguments before this keyword-argument pair.
The following example establishes a virtual link with default values for all optional parameters:
router ospf 201 network 36.0.0.0 0.255.255.255 area 36.0.0.0 area 36.0.0.0 virtual-link 36.3.4.5
A dagger (+) indicates that the command is documented in another chapter.
area authentication
service password-encryption +
show ip ospf
To configure the IS-IS area authentication password, use the area-password router configuration command. To disable the password, use the no form of this command.
area-password password| password | Password you assign. |
No area password is defined.
Router configuration
This password is inserted in Level 1 (station router level) link state PDUs (LSPs), complete sequence number PDUs (CSNPs), and partial sequence number PDUs (PSNP).
The following example assigns an area authentication password:
router isisarea-password angel
To restore the default dehavior of automatic summarization of subnet routes into network-level routes, use the auto-summary router configuration command. To disable this feature, use the no form of this command.
auto-summaryThis command has no arguments or keywords.
Enabled
Router configuration
By default, BGP does not accept subnets redistributed from IGP. To advertise and carry subnet routes in BGP, use an explicit network command or the no auto-summary command. If you disable auto-summarization and have not entered a network command, you will not advertise network routes for networks with subnet routes unless they contain a summary route.
IP Enhanced IGRP summary routes are given an administrative distance value of 5. You cannot configure this value.
In the following example, network numbers are not summarized automatically:
router bgp 6 no auto-summary
The following example disables automatic summarization for router process eigrp 109:
router eigrp 109 no auto-summary
To specify the local autonomous system that the router resides in for EGP, use the autonomous-system global configuration command . To remove the autonomous system number, use the no form of this command.
autonomous-system local-as| local-as | Local autonomous system number to which the router belongs. |
No local autonomous system is specified.
Global configuration
Before you can set up EGP routing, you must specify an autonomous system number. The local autonomous system number will be included in EGP messages sent by the router.
The following sample configuration specifies an autonomous system number of 110:
autonomous-system 110
To specify which autonomous systems belong to a common administration, use the bgp common-as router configuration command. To .remove an autonomous system from the common administration, use the no form of this command.
bgp common-as autonomous-system [autonomous-system ... ]| autonomous-system | Autonomous system numbers that belong to a common administration. |
No common autonomous system is configured.
Router configuration
BGP requires internal BGP (IBGP) neighbors to be fully meshed, which is a processor-intensive situation. One way to reduce the IBGP mesh is to divide the autonomous system (AS) into multiple autonomous systems and specify that they are under common administration. Each AS is fully meshed and has external BGP (EBGP) sessions with the peers in other autonomous systems. Even though the peers in different autonomous systems have EBGP sessions, they exchange routing information as if they are IBGP peers. Specifically, the next-hop and local preference information is preserved. This enables to you to retain a single Interior Gateway Protocol (IGP) for all of the autonomous systems.
An alternative method to handle a fully meshed, internal BGP network is to use the bgp confederation identifier command.
The following example specifies that autonomous systems 100, 200, and 300 belong to a common administration. Neighbor 1.2.3.4 is in remote AS 200 and will get the same information as an internal BGP peer.
router bgp 100 bgp common-as 200 300 neighbor 1.2.3.4 remote-as 200
Tospecify a BGP confederation identifier, use the bgp confederation identifier router configuration command. To remove the confederation identifier, use the no form of this command.
bgp confederation identifier autonomous-system| autonomous-system | Autonomous system number that internally includes multiple autonomous systems. |
No confederation identifier is configured.
Router configuration
Another way to reduce the IBGP mesh is to divide an AS into multiple autonomous systems and group them into a single confederation. Each autonomous system is fully meshed within itself, and has a few connections to another autonomous system in the same confederation. Even though the peers in different autonomous systems have EBGP sessions, they exchange routing information as if they are IBGP peers. Specifically, the next-hop and local preference information is preserved. This enables to you to retain a single Interior Gateway Protocol (IGP) for all of the autonomous systems. To the outside world, the confederation looks like a single autonomous system.
An alternative method toreduce the IBGP mesh is to use the bgp common-as command.
In the following example, the autonomous system is divided into autonomous systems 4001, 4002, 4003, 4004, 4005, 4006, and 4007 and identified by the confederation identifier 5. Neighbor 1.2.3.4 is someone inside your routing domain confederation. Neighbor 3.4.5.6 is someone outside your routing domain confederation. To the outside world, there appears to be a single autonomous system with the number 5.
router bgp 4001 bgp confederation identifier 5 bgp confederation peers 4002 4003 4004 4005 4006 4007 neighbor 1.2.3.4 remote-as 4002 neighbor 3.4.5.6 remote-as 510
bgp common-as
bgp confederation peers
To configure the autonomous systems that belong to the confederation, use the bgp confederation peers router configuration command. Toremove an autonomous system from the confederation, use the no form of this command.
bgp confederation peers autonomous-system [autonomous-system ... ]| autonomous-system | Autonomous system number. |
No confederation peers are configured.
Router configuration
The autonomous systems specified in this command are visible internally to a confederation. Each autonomous system is fully meshed within itself. Thebgp confederation identifier command specifies the confederation that the autonomous systems belong to.
The following example specifies that autonomous systems 1090, 1091, 1092 and 1093 belong to a single confederation:
router bgp 1090 bgp confederation peers 1091 1092 1093
To change the default local preference value, use the bgp default local-preference command. To return to the default setting, use the no form of this command.
bgp default local-preference value| value | Local preference value. Higher is more preferred. Integer from 0 through 4294967295. |
Local preference value of 100
Router configuration
Generally, the default value of 100 allows you to easily define a particular path as less preferable than paths with no local preference attribute. The preference is sent to all routers in the local autonomous system.
In the following example, the default local preference value is raised from the default of 100 to 200:
router bgp 200 bgp default local-preference 200
To immediately reset the BGP sessions of any directly adjacent external peers if the link used to reach them goes down, use the bgp fast-external-fallover router configuration command. To disable this feature, use the no form of this command.
bgp fast-external-falloverThis command has no arguments or keywords.
Enabled
Router configuration
In the following example, the automatic resetting of BGP sessions is disabled:
router bgp 109 no bgp fast-external-fallover
To remove all dynamic entries from the ARP cache and to clear the fast-switching cache, use the clear arp-cache EXEC command.
clear arp-cacheThis command has no arguments or keywords.
EXEC
The following example removes all dynamic entries from the ARP cache and clears the fast-switching cache:
clear arp-cache
To reset a BGP connection, use the clear ip bgp EXEC command at the system prompt.
clear ip bgp {* | address}| * | Resets all current BGP sessions. |
| address | Resets only the identified BGP neighbor. |
EXEC
Use this command whenever any of the following changes occur:
The following example shows how to reset all current BGP sessions:
clear ip bgp *
To delete entries from the neighbor table, use the clear ip eigrp neighbors EXEC command.
clear ip eigrp neighbors [ip-address | interface]| ip-address | (Optional) Address of the neighbor. |
| interface | (Optional) Interface type and number. Specifying this argument removes from the neighbor table all entries learned via this interface. |
EXEC
The following example removes the neighbor whose address is 160.20.8.3:
clear ip eigrp neighbors 160.20.8.3
To delete entries from the IGMP cache, use the clear ip igmp group EXEC command.
clear ip igmp group [group-name | group-address | interface]| group-name | (Optional) Name of the multicast group, as defined in the DNS hosts table or with the ip host command. |
| group-address | (Optional) Address of the multicast group. This is a multicast IP address in four-part dotted notation. |
| interface | (Optional) Interface type and number. |
EXEC
The IGMP cache contains a list of the multicast groups of which hosts on the directly connected LAN are members. If the router has joined a group, it is also listed in the cache.
To delete all entries from the IGMP cache, specify the clear ip igmp group command with no arguments.
The following example clears entries for the multicast group 224.0.255.1 from the IGMP cache:
clear ip igmp group 224.0.255.1
A dagger (+) indicates that the command is documented in another chapter.
ip host +
show ip igmp groups
show ip igmp interface
To delete entries from the IP multicast routing table, use the clear ip mroute EXEC command.
clear ip mroute * | {group-name [source-address] | group-address [source-address]}| * | Deletes all entries from the IP multicast routing table. |
| group-name | Name of the multicast group, as defined in the DNS hosts table or with the ip host command. |
| group-address | Address of the multicast group. This is a multicast IP address in four-part dotted notation. |
| source-address | (Optional) Address of a multicast source that is transmitting to the group. A source does not need to be a member of the group. If you specify source-address, you must specify either group-name or group-address. |
EXEC
The following example deletes all entries from the IP multicast routing table:
clear ip mroute *
The following example deletes from the IP multicast routing table all sources on the 10.3.0.0 subnet that are transmitting to the multicast group 224.2.205.42. Note that this example deletes all sources on network 10.3, not individual sources.
clear ip mroute 224.2.205.42 10.3.0.0
A dagger (+) indicates that the command is documented in another chapter.
ip host +
show ip mroute
To remove one or more routes from the IP routing table, use the clear ip route EXEC command.
clear ip route {network [mask] | *}| network | Network or subnet address to remove. |
| mask | (Optional) Network mask associated with the IP address you wish to remove. |
| * | Removes all entries. |
EXEC
The following example removes a route to network 132.5.0.0 from the IP routing table:
clear ip route 132.5.0.0
show ip route
To control the candidate default routing information between IGRP or Enhanced IGRP processes, use the default-information allowed router configuration command. To suppress IGRP or Enhanced IGRP candidate information in incoming updates, use the no default-information allowed in command. To suppress IGRP or Enhanced IGRP candidate information in outbound updates, use the no default-information allowed out command.
default-information allowed {in | out} [route-map map-tag]| in | Allows IGRP or Enhanced IGRP exterior or default routes to be received by an IGRP process. |
| out | Allows IGRP or Enhanced IGRP exterior routes to be advertised in updates. |
| route-map map-tag | (Optional) Indicates that the route map should be interrogated to filter the importation of routes from this source routing protocol to the current routing protocol. The argument map-tag is the identifier of a configured route map. If you specify route-map without specifying map-tag, no routes are imported. If you omit route-map, all routes are redistributed. |
Normally, exterior routes are always accepted and default information is passed between IGRP or Enhanced IGRP processes when doing redistribution.
Router configuration
The default network of 0.0.0.0 used by RIP cannot be redistributed by IGRP or Enhanced IGRP.
The following example allows IGRP exterior or default routes to be received by the IGRP process in autonomous system 23:
router igrp 23 default-information allowed in
To allow the redistribution of network 0.0.0.0 into BGP, use the default-information originate router configuration command. To disable this feature, use the no form of this command.
default-information originateThis command has no arguments or keywords.
Disabled
Router configuration
The same functionality will result from the network 0.0.0.0 command, using the network router configuration command.
The following example configures BGP to redistribute network 0.0.0.0 into BGP:
router bgp 164 default-information originate
To explicitly configure EGP to generate a default route, use the default-information originate router configuration command. To disable this feature, use the no form of this command.
default-information originateThis command has no arguments or keywords.
Disabled
Router configuration
Because EGP can use network 0.0.0.0 as a default route, EGP must be explicitly configured to generate a default route. If the next hop for the default route can be advertised as a third party, it will be included as a third party.
The following example configures EGP to generate a default route:
autonomous system 109 router egp 164 network 131.108.0.0 network 192.31.7.0 neighbor 10.2.0.2 default-information originate
To generate a default route into an IS-IS routing domain, use the default-information originate router configuration command. To disable this feature, use the no form of this command.
default-information originate [route-map map-name]| originate | Originates the default route regardless of whether it resides in the routing table. |
| route-map map-name | (Optional) Routing process will generate the default route if the route-map is satisfied. |
Disabled
Router configuration
If a router configured with this command has a route to 0.0.0.0 in the routing table, IS-IS will originate an advertisement for 0.0.0.0 in its LSPs.
In the following configuration, the router is forced to generate a default external route into an IS-IS domain:
router isis ! BGP routes will be distributed into IS-IS redistribute bgp 120 ! access list 2 is applied to outgoing routing updates distribute-list 2 out ! metric of 60 is specified for default router redistributed into IS-IS ! routing domain. default-information originate metric 60 ! access list 2 defined as giving access to network 100.105.0.0 access-list 2 permit 100.105.0.0 0.0.255.255
To generate a default route into an OSPF routing domain, use the default-information originate router configuration command. To disable this feature, use the no form of this command.
default-information originate [always] [metric metric-value] [metric-type type-value]| originate | Causes the router to generate a default external route into an OSPF domain if the router already has a default route and you want to propagate to other routers. |
| always | (Optional) Always advertises the default route regardless of whether the router has a default route. |
| metric metric-value | (Optional) Metric used for generating the default route. If you omit a value and do not specify a value using the default-metric router configuration command, the default metric value is 10. The value used is specific to the protocol. |
| metric-type type-value | (Optional) External link type associated with the default route advertised into the OSPF routing domain. It can be one of the following values:
1--Type 1 external route 2--Type 2 external route The default is Type 2 external route. |
| level-1 | Level 1 routes are redistributed into other IP routing protocols independently. It specifies if IS-IS advertises network 0.0.0.0 into the Level 1 area. |
| level-1-2 | Both Level 1 and Level 2 routes are redistributed into other IP routing protocols. It specifies if IS-IS advertises network 0.0.0.0 into both levels in a single command. |
| level-2 | Level 2 routes are redistributed into other IP routing protocols independently. It specifies if IS-IS advertises network 0.0.0.0 into the Level 2 subdomain. |
| route-map map-name | (Optional) Routing process will generate the default route if the route-map is satisfied. |
Disabled
Router configuration
Whenever you use the redistribute or the default-information router configuration commands to redistribute routes into an OSPF routing domain, the router automatically becomes an autonomous system boundary router. However, an autonomous system boundary router does not, by default, generate a default route into the OSPF routing domain. The router still needs to have a default route for itself before it generates one, except when you have specified the always keyword.
When you use this command for the OSPF process, the default network must reside in the routing table and you must satisfy the route-map map-name keyword. Use the default-information originate always route-map map-name form of the command when you do not want the dependency on the default network in the routing table.
The following example specifies a metric of 100 for the default route redistributed into the OSPF routing domain and an external metric type of Type 1:
router ospf 109 redistribute igrp 108 metric 100 subnets default-information originate metric 100 metric-type 1
To set default metric values for the BGP, EGP, OSPF, and RIP routing protocols, use this form of the default-metric router configuration command. To return to the default state, use the no form of this command.
default-metric number| number | Default metric value appropriate for the specified routing protocol |
Built-in, automatic metric translations, as appropriate for each routing protocol
Router configuration
The default-metric command is used in conjunction with the redistribute router configuration command to cause the current routing protocol to use the same metric value for all redistributed routes. A default metric helps solve the problem of redistributing routes with incompatible metrics. Whenever metrics do not convert, using a default metric provides a reasonable substitute and enables the redistribution to proceed.
In BGP, this sets the MULTI_EXIT_DISC metric. (The name of this metric for BGP Versions 2 and 3 is INTER_AS.)
The following example shows a router in autonomous system 109 using both the RIP and the OSPF routing protocols. The example advertises OSPF-derived routes using the RIP protocol and assigns the IGRP-derived routes a RIP metric of 10.
router rip default-metric 10 redistribute ospf 109
To set metrics for IGRP or Enhanced IGRP, use this form of the default-metric router configuration command. To remove the metric value and return to the default state, use the no form of this command.
default-metric bandwidth delay reliability loading mtu| bandwidth | Minimum bandwidth of the route in kilobits per second. It can be 0 or any positive integer. |
| delay | Route delay in tens of microseconds. It can be 0 or any positive number that is a multiple of 39.1 nanoseconds. |
| reliability | Likelihood of successful packet transmission expressed as a number between 0 and 255. The value 255 means 100 percent reliability, and the value 0 means no reliability. |
| loading | Effective bandwidth of the route expressed as a number from 0 to 255 (255 is 100 percent loading). |
| mtu | Minimum maximum transmission unit (MTU) size of the route in bytes. It can be 0 or any positive integer. |
Disabled
Router configuration
Metric defaults have been carefully set to work for a wide variety of networks. Take great care in changing these values.
Keeping the same metrics is supported only when redistributing from IGRP, Enhanced IGRP, or static routes.
The following example takes redistributed RIP metrics and translates them into IGRP metrics with values as follows: bandwidth = 1000, delay = 100, reliability = 250, loading = 100, and mtu =1500.
router igrp 109 network 131.108.0.0 redistribute rip default-metric 1000 100 250 100 1500
To define an administrative distance, use the distance router configuration command. To remove a distance definition, use the no form of this command.
distance weight [address mask [access-list-number]] [ip]| weight | Administrative distance. This can be an integer from 10 to 255. (The values 0 through 9 are reserved for internal use.) Used alone, the argument weight specifies a default administrative distance that the router uses when no other specification exists for a routing information source. Routes with a distance of 255 are not installed in the routing table. |
| address | (Optional) IP address in four-part dotted notation. |
| mask | (Optional) IP address mask in four-part dotted-decimal format. A bit set to 1 in the mask argument instructs the router to ignore the corresponding bit in the address value. |
| access-list-number | (Optional) Number of a standard IP access list to be applied to incoming routing updates. |
| ip | (Optional) IP-derived routes for IS-IS. It can be applied independently for IP routes and ISO CLNS routes. |
Table 18-1 lists default administrative distances.
| Route Source | Default Distance |
|---|---|
| Connected interface | 0 |
| Static route | 1 |
| External BGP | 20 |
| IGRP | 100 |
| OSPF | 110 |
| IS-IS | 115 |
| RIP | 120 |
| EGP | 140 |
| Internal BGP | 200 |
| Unknown | 255 |
Router configuration
Numerically, an administrative distance is an integer between 0 and 255. In general, the higher the value, the lower the trust rating. An administrative distance of 255 means the routing information source cannot be trusted at all and should be ignored.
When the optional access list number is used with this command, it is applied when a network is being inserted into the routing table. This behavior allows filtering of networks according to the IP address of the router supplying the routing information. This could be used, as an example, to filter out possibly incorrect routing information from routers not under your administrative control.
The order in which you enter distance commands can affect the assigned administrative distances in unexpected ways (see "Example" for further clarification).
Weight values are also subjective; there is no quantitative method for choosing weight values.
For BGP, the distance command sets the administrative distance of the External BGP route.
The show ip protocols EXEC command displays the default administrative distance for a specified routing process.
In the following example, the router igrp global configuration command sets up IGRP routing in autonomous system number 109. The network router configuration commands specify IGRP routing on networks 192.31.7.0 and 128.88.0.0. The first distance router configuration command sets the default administrative distance to 255, which instructs the router to ignore all routing updates from routers for which an explicit distance has not been set. The second distance command sets the administrative distance for all routers on the Class C network 192.31.7.0 to 90. The third distance command sets the administrative distance for the router with the address 128.88.1.3 to 120.
router igrp 109 network 192.31.7.0 network 128.88.0.0 distance 255 distance 90 192.31.7.0 0.0.0.255 distance 120 128.88.1.3 0.0.0.0
To allow the use of external, internal, and local administrative distances that could be a better route to a node, use the distance bgp router configuration command. To return to the default values, use the no form of this command.
distance bgp external-distance internal-distance local-distance| external-distance | Administrative distance for BGP external routes. External routes are routes for which the best path is learned from a neighbor external to the autonomous system. Acceptable values are from 1 to 255. The default is 20. Routes with a distance of 255 are not installed in the routing table. |
| internal-distance | Administrative distance for BGP internal routes. Internal routes are those routes that are learned from another BGP entity within the same autonomous system. Acceptable values are from 1 to 255. The default is 200. Routes with a distance of 255 are not installed in the routing table. |
| local-distance | Administrative distance for BGP local routes. Local routes are those networks listed with a network router configuration command, often as back doors, for that router or for networks that are being redistributed from another process. Acceptable values are from 1 to 255. The default is 200. Routes with a distance of 255 are not installed in the routing table. |
external-distance: 20
internal-distance: 200
local-distance: 200
Router configuration
An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. Numerically, an administrative distance is an integer between 0 and 255. In general, the higher the value, the lower the trust rating. An administrative distance of 255 means the routing information source cannot be trusted at all and should be ignored.
Use this command if another protocol is known to be able to provide a better route to a node than was actually learned via external BGP, or if some internal routes should really be preferred by BGP.
In the following example, internal routes are known to be preferable to those learned through the IGP, so the administrative distance values are set accordingly:
router bgp 109 network 131.108.0.0 neighbor 129.140.6.6 remote-as 123 neighbor 128.125.1.1 remote-as 47 distance bgp 20 20 200
To allow the use of two administrative distances--internal and external--that could be a better route to a node, use the distance eigrp router configuration command. To reset these values to their defaults, use the no form of this command.
distance eigrp internal-distance external-distance| internal-distance | Administrative distance for Enhanced IGRP internal routes. Internal routes are those that are learned from another entity within the same autonomous system. It can be a value from 1 to 255. |
| external-distance | Administrative distance for Enhanced IGRP external routes. External routes are those for which the best path is learned from a neighbor external to the autonomous system. It can be a value from 1 to 255. |
internal-distance: 90
external-distance: 170
Router configuration
An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. Numerically, an administrative distance is an integer between 0 and 255. In general, the higher the value, the lower the trust rating. An administrative distance of 255 means the routing information source cannot be trusted at all and should be ignored.
Use the distance eigrp command if another protocol is known to be able to provide a better route to a node than was actually learned via external Enhanced IGRP or if some internal routes should really be preferred by Enhanced IGRP.
Table 18-2 lists the default administrative distances.
| Route Source | Default Distance |
|---|---|
| Connected interface | 0 |
| Static route | 1 |
| Enhanced IGRP summary route | 5 |
| External BGP | 20 |
| Internal enhanced IGRP | 90 |
| IGRP | 100 |
| OSPF | 110 |
| IS-IS | 115 |
| RIP | 120 |
| EGP | 140 |
| External enhanced IGRP | 170 |
| Internal BGP | 200 |
| Unknown | 255 |
To display the default administrative distance for a specified routing process, use the show ip protocols EXEC command.
In the following example, the router eigrp global configuration command sets up Enhanced IGRP routing in autonomous system number 109. The network router configuration commands specify Enhanced IGRP routing on networks 192.31.7.0 and 128.88.0.0. The first distance router configuration command sets the default administrative distance to 255, which instructs the router to ignore all routing updates from routers for which an explicit distance has not been set. The second distance router configuration command sets the administrative distance for all routers on the Class C network 192.31.7.0 to 90. The third distance router configuration command sets the administrative distance for the router with the address 128.88.1.3 to 120.
router eigrp 109 network 192.31.7.0 network 128.88.0.0 distance 255 ! ! use caution when executing the next two commands! ! distance 90 192.31.7.0 0.0.0.255 distance 120 128.88.1.3 0.0.0.0
To filter networks received in updates, use the distribute-list in router configuration command. To change or cancel the filter, use the no form of this command.
distribute-list access-list-number in [interface-name]| access-list-number | Standard IP access list number. The list defines which networks are to be received and which are to be suppressed in routing updates. |
| in | Applies the access list to incoming routing updates. |
| interface-name | (Optional) Interface on which the access list should be applied to incoming updates. If no interface is specified, the access list will be applied to all incoming updates. |
Disabled
Router configuration
This command is not supported in IS-IS.
In the following example, the Enhanced IGRP routing process accepts only two networks--network 0.0.0.0 and network 131.108.0.0:
access-list 1 permit 0.0.0.0 access-list 1 permit 131.108.0.0 access-list 1 deny 0.0.0.0 255.255.255.255 router eigrp network 131.108.0.0 distribute-list 1 in
A dagger (+) indicates that the command is documented in another chapter.
access-list (standard)+
access-list (extended)
distribute-list out
redistribute
To suppress networks from being advertised in updates, use the distribute-list out router configuration command. To cancel this function, use the no form of this command.
distribute-list access-list-number out [interface-name | routing-process || access-list-number | Standard IP access list number. The list defines which networks are to be sent and which are to be suppressed in routing updates. |
| out | Applies the access list to outgoing routing updates. |
| interface-name | (Optional) Name of a particular interface. |
| routing-process | (Optional) Name of a particular routing process, or the keyword static or connected. |
| autonomous-system-number | (Optional) Autonomous system number. |
Disabled
Router configuration
When redistributing networks, a routing process name can be specified as an optional trailing argument to the distribute-list command. This causes the access list to be applied to only those routes derived from the specified routing process. After the process-specific access list is applied, any access list specified by a distribute-list command without a process name argument will be applied. Addresses not specified in the distribute-list command will not be advertised in outgoing routing updates.
The following example would cause only one network to be advertised by a RIP routing process: network 131.108.0.0.
access-list 1 permit 131.108.0.0 access-list 1 deny 0.0.0.0 255.255.255.255 router rip network 131.108.0.0 distribute-list 1 out
In the following example, access list 1 is applied to outgoing routing updates and IS-IS is enabled on interface Ethernet 0. Only network 131.131.101.0 will be advertised in outgoing IS-IS routing updates.
router isis redistribute ospf 109 distribute-list 1 out interface Ethernet 0 ip router isis access-list 1 permit 131.131.101.0 0.0.0.255
A dagger (+) indicates that the command is documented in another chapter.
access-list (standard) +
access-list (extended)+
distribute-list in
redistribute
To configure the IS-IS routing domain authentication password, use the domain-password router configuration command. To disable a password, use the no form of this command.
domain-password password| password | Password you assign. |
No password is specified.
Router configuration
This password is inserted in Level 2 (area router level) link state PDUs (LSPs), complete sequence number PDUs (CSNPs), and partial sequence number PDUs (PSNP).
The following example assigns an authentication password to the routing domain:
router isis domain-password flower
To specify the IP address on an interface, use the ip address interface configuration command. To remove an address, use the no form of this command.
ip address address mask [secondary]| address | IP address. |
| mask | IP address mask. |
| secondary | (Optional) Address to be added as a secondary address. |
Disabled
Interface configuration
The optional keyword secondary allows an unlimited number of secondary addresses to be specified. Secondary addresses are treated like primary addresses, except that the system never generates datagrams other than routing updates with secondary source addresses. IP broadcasts and ARP requests are handled properly, as are interface routes in the IP routing table.
Secondary IP addresses can be used in a variety of situations. The following are the most common applications:
The following example specifies 131.108.1.27 as the primary address and 192.31.7.17 as a secondary address for interface Ethernet 0:
interface ethernet 0 ip address 131.108.1.27 255.255.255.0 ip address 192.31.7.17 255.255.255.0 secondary
To define a BGP-related access list, use the ip as-path access-list global configuration command. To disable use of the access list, use the no form of this command.
ip as-path access-list access-list-number {permit | deny} as-regular-expression| access-list-number | Integer from 1 to 199 that indicates the regular expression access list number. |
| permit | Permits access for matching conditions. |
| deny | Denies access to matching conditions. |
| as-regular-expression | Autonomous system in the access list using a regular expression. See the "Regular Expressions" appendix for information about forming regular expressions. |
No access lists are defined.
Global configuration
You can specify an access list filter on both inbound and outbound BGP routes. In addition, you can assign weights based on a set of filters. Each filter is an access list based on regular expressions. If the regular expression matches the representation of the autonomous system path of the route as an ASCII string, then the permit or deny condition applies. The autonomous system path does not contain the local autonomous system number. Use the ip as-path access-list global configuration command to define an BGP access list, and the neighbor router configuration command to apply a specific access list.
See the "Regular Expressions" appendix for information on forming regular expressions.
The following example specifies that the BGP neighbor with IP address 128.125.1.1 is not sent advertisements about any path through or from the adjacent autonomous system 123.
ip as-path access-list 1 deny _123_ ip as-path access-list 1 deny ^123 .* ! The space in the above expression (^123.*) is required. router bgp 109 network 131.108.0.0 neighbor 129.140.6.6 remote-as 123 neighbor 128.125.1.1 remote-as 47 neighbor 128.125.1.1 filter-list 1 out
neighbor distribute-list
neighbor filter-list
To create a community list for BGP and control access to it, use the ip community-list global configuration command. To delete the community list, use the no form of this command.
ip community-list community-list-number {permit | deny} community-number| community-list-number | Integer 1 through 99 that identifies one or more permit or deny groups of communities. |
| permit | Permits access for a matching condition. |
| deny | Denies access for a matching condition. |
| community-number | Community number configured by a set community command. Valid value is one of the following:
· 1 through 4294967200. You can specify a single number or multiple numbers separated by a space. · internet--The Internet community. · no-export--Do not advertise this route to an EBGP peer. · no-advertise--Do not advertise this route to any peer (internal or external). |
Once you permit a value for the community number, the community list defaults to an implicit deny for everything else that has not been permitted.
Global configuration
In the following example, the router permits all routes except the routes with the communities 5 and 10 or 10 and 15:
ip community-list 1 deny 5 10 ip community-list 1 deny 10 15 ip community-list 1 permit internet
To select a network as a candidate route for computing the gateway of last resort, use the ip default-network global configuration command. To remove a route, use the no form of this command.
ip default-network network-number| network-number | Number of the network. |
If the router has a directly connected interface onto the specified network, the dynamic routing protocols running on that router will generate (or source) a default route. For RIP, this is flagged as the pseudonetwork 0.0.0.0; for IGRP, it is the network itself, flagged as an exterior route.
Global configuration
The router uses both administrative distance and metric information to determine the default route. Multiple ip default-network commands can be given. All candidate default routes, both static (that is, flagged by ip default-network) and dynamic, appear in the routing table preceded by an asterisk.
If the IP routing table indicates that the specified network number is subnetted and a non-zero subnet number is specified, then the system will automatically configure a static summary route. This static summary route is configured instead of a default network. The effect of the static summary route is to cause traffic destined for subnets that are not explicitly listed in the IP routing table to be routed using the specifed subnet.
The following example defines a static route to network 10.0.0.0 as the static default route:
ip route 10.0.0.0 255.0.0.0 131.108.3.4 ip default-network 10.0.0.0
If the following command was issued on a router not connected to network 129.140.0.0, the router might choose the path to that network as a default route when the network appeared in the routing table:
ip default-network 129.140.0.0
To configure an acceptance filter for incoming DVMRP reports, use the ip dvmrp accept-filter interface configuration command. To disable this feature, use the no form of this command.
ip dvmrp accept-filter access-list-number [distance]| access-list-number | Number of a standard IP access list. This can be a number from 0 to 99. A value of 0 means that all sources are accepted with the configured distance. |
| distance | (Optional) Administrative distance to the destination. |
All destinations are accepted with a distance of 0.
Interface configuration
Any sources that match the access list are stored in the DVMRP routing table.
The route with the lower distance (either the route in the unicast routing table or that in the DVMRP routing table) takes precedence when computing the Reverse Path Forwarding (RPF) interface for a source of a multicast packet.
By default, the administrative distance for DVMRP routes is 0. This means that they always take precedence over unicast routing table routes. If you have two paths to a source, one through unicast routing (using PIM as the multicast routing protocol) and another path using DVMRP (unicast and multicast routing), and if you want to use the PIM path, use the ip dvmrp accept-filter command to increase the administrative distance for DVMRP routes. For example, if the unicast routing protocol is Enhanced IGRP, which has a default administrative distance of 90, you could define and apply the following access list so the RPF interface used to accept multicast packets will be through the Enhanced IGRP/PIM path:
ip dvmrp accept-filter 1 100 access-list 1 permit 0.0.0.0 255.255.255.255
The following example applies access list 57 to the interface and sets a distance of 4:
access-list 57 permit 131.108.0.0 0.0.255.255 access-list 57 permit 198.92.37.0 0.0.0.255 access-list 57 deny 0.0.0.0 255.255.255.255 ip dvmrp accept-filter 57 4
A dagger (+) indicates that the command is documented in another chapter.
distance
ip dvmrp metric
show ip dvmrp route
tunnel mode +
To advertise network 0.0.0.0 to DVMRP neighbors on an interface, use the ip dvmrp default-information interface configuration command. To prevent the advertisement, use the no form of this command.
ip dvmrp default-information {originate | only}| originate | Other routes more specific than 0.0.0.0 can also be advertised. |
| only | No DVMRP routes other than 0.0.0.0 are advertised. |
Disabled
Interface configuration
This command should only be used when the router is a neighbor to mrouted version 3.4 machines. The mrouted protocol is a public domain implementation of DVMRP.
You can use the ip dvmrp metric command with the ip dvmrp default-information command to tailor the metric used when advertising the default route 0.0.0.0. By default, metric 1 is used.
The following example configures the router to advertise network 0.0.0.0, in addition to other networks, to DVMRP neighbors:
ip dvmrp default-information originate
To configure the metric associated with a set of destinations for DVMRP reports, use the ip dvmrp metric interface configuration command. To disable this function, use the no form of this command.
ip dvmrp metric metric [access-list-number] [protocol process-id]| metric | Metric associated with a set of destinations for DVMRP reports. It can be a value from 0 to 32. A value of 0 means that the route is not advertised. A value of 32 is equivalent to infinity (unreachable). |
| access-list-number | (Optional) Number of an access list. If you specify this argument, only the multicast destinations that match the access list are reported with the configured metric. Any destinations not advertised because of split horizon do not use the configured metric. |
| protocol | (Optional) Name of unicast routing protocol. It can be bgp, egp, eigrp, igrp, isis, ospf, rip, or static. (Note that these are the protocol names you can specify with a router protocol command.)
If you specify these arguments, only routes learned by the specified routing protocol are advertised in DVMRP report messages. |
| process-id | (Optional) Process ID number of the unicast routing protocol. |
No metric is preconfigured. Only directly connected subnets and networks are advertised to neighboring DVMRP routers.
Interface configuration
When PIM is configured on an interface and DVMRP neighbors are discovered, the router sends DVMRP report messages for directly connected networks. The ip dvmrp metric command enables DVMRP report messages for multicast destinations that match the access list. Usually, the metric for these routes is 1. Under certain circumstances, it may be desirable to tailor the metric used for various unicast routes.
Use the access-list-number argument in conjunction with the protocol process-id arguments to selectively list the destinations learned from a given routing protocol.
To display DVMRP activity, use the debug ip dvmrp command.
The following example connects a PIM cloud to a DVMRP cloud. Access list 1 permits the sending of DVMRP reports to the DVMRP routers advertising all sources in the 198.92.35.0 network with a metric of 1. Access list 2 permits all other destinations, but the metric of 0 means that no DVMRP reports are sent for these destinations.
access-list 1 permit 198.92.35.0 0.0.0.255 access-list 1 deny 0.0.0.0 255.255.255.255 access-list 2 permit 0.0.0.0 255.255.255.255 interface tunnel 0 ip dvmrp metric 1 1 ip dvmrp metric 0 2
Two daggers (++) indicate that the command is documented in the Debug Command Reference publication.
debug ip dvmrp ++
ip dvmrp accept-filter
To enable GDP routing on an interface, use the ip gdp interface configuration command. To disable GDP routing, use the no form of this command.
ip gdp [priority number | reporttime seconds | holdtime seconds]| priority number | (Optional) Alters the GDP priority; default is a priority of 100. A larger number indicates a higher priority. |
| reporttime seconds | (Optional) Alters the GDP reporting interval; the default is 5 seconds for broadcast media such as Ethernets, and never for nonbroadcast media such as X.25. |
| holdtime seconds | (Optional) Alters the GDP default hold time of 15 seconds. |
priority: 100
reporttime: 5 seconds for broadcast media; 0 for nonbroadcast media
holdtime: 15 seconds
Interface configuration
When enabled on an interface, GDP updates report the primary and secondary IP addresses of that interface.
In the following example, GDP is enabled on interface Ethernet 1 with a report time of 10 seconds, and priority and hold time set to their defaults (because none are specified):
ip gdp reporttime 10
To configure the hello interval for the Enhanced IGRP routing process designated by an autonomous system number, use the ip hello-interval eigrp interface configuration command. To restore the default value, use the no form of this command.
ip hello-interval eigrp autonomous-system-number seconds| autonomous-system-number | Autonomous system number. |
| seconds | Hello interval, in seconds. |
5 seconds
Interface configuration
The following example sets the hello interval for interface Ethernet 0 to 10 seconds:
interface ethernet 0 ip hello-interval eigrp 109 10
To configure the hold time for the Enhanced IGRP routing process designated by the autonomous system number, use the ip hold-time eigrp interface configuration command. To restore the default value, use the no form of this command.
ip hold-time eigrp autonomous-system-number seconds| autonomous-system-number | Autonomous system number. |
| seconds | Hold time, in seconds. |
15 seconds
Interface configuration
The hold time is three times the hello interval. If the current value for the hold time is less than two times the hello interval, the hold time is reset.
If a router does not receive a hello packet within the specified hold time, routes through the router are considered unavailable.
Increasing the hold time delays route convergence across the network.
The following example sets the hold time for Ethernet interface 0 to 40 seconds:
interface ethernet 0 ip hold-time eigrp 109 40
To control the multicast groups that hosts on the subnet serviced by an interface can join, use the ip igmp access-group interface configuration command. To disable groups on an interface, use the no form of this command.
ip igmp access-group access-list-number| access-list-number | Number of a standard IP access list. This can be a number from 1 to 99. |
All groups are allowed on an interface.
Interface configuration
In the following example, hosts serviced by Ethernet interface 0 can join the group 225.2.2.2 only:
access-list 1 225.2.2.2 0.0.0.0 interface ethernet 0 ip igmp access-group 1
To have the router join a multicast group, use the ip igmp join-group interface configuration command. To cancel membership in a multicast group, use the no form of this command.
ip igmp join-group group-address| group-address | Address of the multicast group. This is a multicast IP address in four-part dotted notation. |
No multicast group memberships are predefined.
Interface configuration
IP packets that are addressed to the group address are passed to the IP client process in the router.
If all the multicast-capable routers that you administer are members of a multicast group, pinging that group causes all routers to respond. This can be a useful administrative and debugging tool.
Another reason to have a router join a multicast group is when other hosts on the network have a bug in IGRP that prevents them from correctly answering IGMP queries. Having the router join the multicast group causes upstream routers to maintain multicast routing table information for that group and keep the paths for that group active.
In the following example, the router joins multicast group 225.2.2.2:
ip igmp join-group 225.2.2.2
A dagger (+) indicates that the command is documented in another chapter.
ip igmp access-group
ping (user) +
ping (privileged)+
To configure the frequency at which the router sends IGMP host-query messages, use the ip igmp query-interval interface configuration command. To return to the default frequency, use the no form of this command.
ip igmp query-interval seconds| seconds | Frequency, in seconds, at which to transmit IGMP host-query messages. The can be a number from 0 to 65535. The default is 60 seconds. |
60 seconds
Interface configuration
Multicast routers send host membership query messages (referred to as host-query messages) to discover which multicast groups have members on the router's attached networks. Hosts respond with IGMP report messages indicating that they wish to receive multicast packets for specific groups (that is, indicating that the host wants to become a member of the group). Host-query messages are addresses to the all-hosts multicast group, which has the address 224.0.0.1, and have an IP TTL value of 1.
The designated router for a LAN is the only router that sends IGMP host-query messages. The designated router is elected according to the multicast routing protocol that runs on the LAN.
The following example changes the frequency at which the designated router sends IGMP host-query messages to 2 minutes:
interface tunnel 0 ip igmp query-interval 120
ip pim query-interval
show ip igmp groups
To enable ICMP Router Discovery Protocol (IRDP) processing on an interface, use the ip irdp interface configuration command. To disable IRDP routing, use the no form of this command.
ip irdp [multicast | holdtime seconds | maxadvertinterval seconds | minadvertinterval| multicast | (Optional) Use the multicast address (224.0.0.1) instead of IP broadcasts. |
| holdtime seconds | (Optional) Length of time in seconds advertisements are held valid. Default is three times the maxadvertinterval value. Must be greater than maxadvertinterval and cannot be greater than 9000 seconds. |
| maxadvertinterval seconds | (Optional) Maximum interval in seconds between advertisements. The default is 600 seconds. |
| minadvertinterval seconds | (Optional) Minimum interval in seconds between advertisements. The default is 0.75 times the maxadvertinterval. If you change the maxadvertinterval value, this value defaults to three-quarters of the new value. |
| preference number | (Optional) Router's preference value. The allowed range is -231 to 231. The default is 0. A higher value increases the router's preference level. You can modify a particular router so that it will be the preferred router to which others home. |
| address address [number] | (Optional) IP address (address) to proxy-advertise, and optionally, its preference value (number). |
Disabled.
When enabled, IRDP uses these defaults:
Interface configuration
If you change maxadvertinterval, the other two values also change, so it is important to change maxadvertinterval first before changing either holdtime or minadvertinterval.
The ip irdp multicast command allows for compatibility with Sun Microsystems Solaris, which requires IRDP packets to be sent out as multicasts. Many implementations cannot receive these multicasts; ensure end host ability before using this command.
The following example illustrates how to set the various IRDP processes:
! enable irdp on interface Ethernet 0 interface ethernet 0 ip irdp ! send IRDP advertisements to the multicast address ip irdp multicast ! increase router preference from 100 to 50 ip irdp preference 50 ! set maximum time between advertisements to 400 secs ip irdp maxadvertinterval 400 ! set minimum time between advertisements to 100 secs ip irdp minadvertinterval 100 ! advertisements are good for 6000 seconds ip irdp holdtime 6000 ! proxy-advertise 131.108.14.5 with default router preference ip irdp address 131.108.14.5 ! proxy-advertise 131.108.14.6 with preference of 50 ip irdp address 131.108.14.6 50
To enable IP multicast routing on the router, use the ip multicast-routing global configuration command. To disable IP multicast routing, use the no form of this command.
ip multicast-routingThis command has no arguments or keywords.
IP multicast routing is disabled.
Global configuration
When IP multicast routing is disabled, the router does not forward any multicast packets.
The following example enables IP multicast routing on the router:
ip multicast-routing
To configure the time-to-live (TTL) threshold of packets being forwarded out an interface, use the ip multicast-threshold interface configuration command. To return to the default TTL threshold, use the no form of this command.
ip multicast-threshold ttl| ttl | Time-to-live value, in hops. It can be a value from 0 to 255. The default value is 0, which means that all multicast packets are forwarded out the interface. |
0, which means that all multicast packets are forwarded out the interface.
Interface configuration
Any multicast packets with a TTL value less than the threshold are not forwarded out the interface.
You should configure the TTL threshold only on border routers. Conversely, routers on which you configure a TTL threshold value automatically become border routers.
In the following example, you set the TTL threshold on a border router to 200, which is a very high value. This means that multicast packets must have a TTL greater than 200 in order to be forwarded out this interface. Multicast applications generally set this value well below 200. Therefore, setting a value of 200 means that no packets will be forwarded out the interface.
interface tunnel 0 ip multicast-threshold 200
To assign a password to be used by neighboring routers that are using OSPF's simple password authentication, use the ip ospf authentication-key interface configuration command. To remove a previously assigned OSPF password, use the no ip form of this command.
ip ospf authentication-key password| password | Any continuous string of characters that can be entered from the keyboard up to 8 bytes in length. |
No password is specified.
Interface configuration
The password created by this command is used as a "key" that is inserted directly into the OSPF header when the router originates routing protocol packets. A separate password can be assigned to each network on a per-interface basis. All neighboring routers on the same network must have the same password to be able to exchange OSPF information.
In the following example, the authentication key is enabled with the string yourpass:
ip ospf authentication-key yourpass
To explicitly specify the cost of sending a packet on an interface, use the ip ospf cost interface configuration command. To reset the path cost to the default value, use the no form of this command.
ip ospf cost cost| cost | Unsigned integer value expressed as the link state metric. It can be a value in the range 1 to 65535. |
No defa