IP Routing Protocols Commands

Syntax Description

Default

Disabled

Command Mode

Router configuration

Usage Guidelines

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 Do not use this form of aggregate-address when aggregating many paths, because this route must be continually withdrawn and re-updated as autonomous system path reachability information for the summarized routes changes.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 autonomous system path access lists match clauses are supported.

Example

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 5

aggregate-address 193.0.0.0 255.0.0.0 as-set

Related Commands

match as-path
match ip address
route-map

Syntax Description

Default

Type 0 authentication (no authentication)

Command Mode

Router configuration

Usage Guidelines

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 communication servers in an area. The authentication password for all OSPF communication servers 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.

Example

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

Related Commands

area default-cost
area stub
ip ospf authentication-key

Syntax Description

Default

Cost of 1

Command Mode

Router configuration

Usage Guidelines

This command is used only on an Area Border Router (ABR) 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 communication servers 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 ABR attached to the stub area. The default-cost option provides the metric for the summary default route generated by the ABR into the stub area.

Example

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

Related Commands

area authentication
area stub

Default

Disabled

Command Mode

Router configuration

Usage Guidelines

Multiple area router configuration commands specifying the range option can be configured. Thus, OSPF can summarize addresses for many different sets of address ranges.

Example

The following example specifies one summary route to be advertised by the communication server acting as an ABR 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

Syntax Description

Default

No stub area is defined.

Command Mode

Router configuration

Usage Guidelines

This command must be configured on all communication servers in the stub area. Use the area router configuration command with the default-cost option to specify the cost of a default internal communication server sent into a stub area by a communication server acting as an Area Border Router (ABR).

There are two stub area router configuration commands: the stub and default-cost options of the area router configuration command. In all communication servers 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 ABR attached to the stub area. The default-cost option provides the metric for the summary default route generated by the ABR into the stub area.

Example

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

Related Commands

area authentication
area default-cost

Syntax Description

Default

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.

Command Mode

Router configuration

Usage Guidelines

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 communication server 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.

Example

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

Related Command

A dagger (†) indicates that the command is documented in another chapter.

area authentication
service password-encryption ^†
show ip ospf

Syntax Description

Default

No local autonomous system is specified.

Command Mode

Global configuration

Usage Guidelines

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 communication server.

Example

The following sample configuration specifies an autonomous system number of 110:

autonomous-system 110

Related Command

router egp

Syntax Description

This command has no arguments or keywords.

Default

Enabled

Command Mode

Router configuration

Usage Guidelines

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.

Example

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

Related Command

ip summary-address eigrp

Syntax Description

This command has no arguments or keywords.

Default

Enabled

Command Mode

Router configuration

Example

In the following example, the automatic resetting of BGP sessions is disabled:

router bgp 109
no bgp fast-external-fallover

Syntax Description

This command has no arguments or keywords.

Command Mode

EXEC

Example

The following example removes all dynamic entries from the ARP cache and clears the fast-switching cache:

clear arp-cache

Syntax Description

Command Mode

EXEC

Usage Guidelines

Use this command whenever any of the following changes occur:

• Additions or changes to the BGP-related access lists
  
  
• Changes to BGP-related weights
  
  
• Changes to BGP-related distribution lists
  
  
• Changes in the BGP timer's specifications
  
  
• Changes to the BGP administrative distance
  
  

Example

The following example resets all current BGP sessions:

clear ip bgp *

Related Commands

show ip bgp
timers bgp

Syntax Description

Command Mode

EXEC

Example

The following example removes the neighbor whose address is 160.20.8.3:

clear ip eigrp neighbors 160.20.8.3

Related Command

show ip eigrp neighbors

Syntax Description

Command Mode

EXEC

Usage Guidelines

The IGMP cache contains a list of the multicast groups of which hosts on the directly connected LAN are members. If the communication server 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.

Example

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

Related Commands

A dagger (†) indicates that the command is documented in another chapter.

ip host ^†
show ip igmp groups
show ip igmp interface

Syntax Description

Command Mode

EXEC

Examples

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

Related Commands

A dagger (†) indicates that the command is documented in another chapter.

ip host ^†
show ip mroute

Syntax Description

Command Mode

EXEC

Example

The following example removes a route to network 132.5.0.0 from the IP routing table:

clear ip route 132.5.0.0

Related Command

show ip route

Syntax Description

Default

Normally, exterior routes are always accepted and default information is passed between IGRP processes when doing redistribution.

Command Mode

Router configuration

Usage Guidelines

The default network of 0.0.0.0 used by RIP cannot be redistributed by IGRP or IP Enhanced IGRP.

Example

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
 

The following example allows IP Enhanced IGRP exterior or default routes to be received by the IP Enhanced IGRP process in autonomous system 23:

router eigrp 23
default-information allowed in

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Router configuration

Usage Guidelines

The same functionality will result from the network 0.0.0.0 command, using the network router configuration command.

Example

The following example configures BGP to redistribute network 0.0.0.0 into BGP:

router bgp 164
default-information originate
 

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Router configuration

Usage Guidelines

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.

Example

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

Syntax Description

Default

Disabled

Command Mode

Router configuration

Usage Guidelines

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.

Examples

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

Related Command

redistribute

Syntax Description

Default

Built-in, automatic metric translations, as appropriate for each routing protocol

Command Mode

Router configuration

Usage Guidelines

This 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.)

Example

The following example shows a communication server in autonomous system 109 using both the RIP and the IGRP routing protocols. The example advertises IGRP-derived routes using the RIP protocol and assigns the IGRP-derived routes a RIP metric of 10.

router rip
default-metric 10
redistribute igrp 109

Related Command

redistribute

Syntax Description

Default

Built-in, automatic metric translations

Command Mode

Router configuration

Usage Guidelines

IGRP metric defaults have been carefully set to work for a wide variety of networks. Take great care in changing these values.

Automatic metric translations for IGRP are only supported when redistributing from IGRP or static.

Example

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

Related Command

redistribute

Syntax Description

Default

Command Mode

Router configuration

Usage Guidelines

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 communication server supplying the routing information. This could be used, as an example, to filter out possibly incorrect routing information from communication servers 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.

Example

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 communication server to ignore all routing updates from communication servers for which an explicit distance has not been set. The second distance command sets the administrative distance for all communication servers on the Class C network 192.31.7.0 to 90. The third distance command sets the administrative distance for the communication server 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

Related Command

distance bgp

Syntax Description

Default

external-distance: 20
internal-distance: 200
local-distance: 200

Command Mode

Router configuration

Usage Guidelines

An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual communication server or a group of communication servers. 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.

Example

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

Related Command

distance

Syntax Description

Default

internal-distance: 90
external-distance: 170

Command Mode

Router configuration

Usage Guidelines

An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual communication server or a group of communication servers. 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 IP Enhanced IGRP or if some internal routes should really be preferred by IP Enhanced IGRP.

To display the default administrative distance for a specified routing process, use the show ip protocols EXEC command.

Example

In the following example, the router eigrp global configuration command sets up IP Enhanced IGRP routing in autonomous system number 109. The network router configuration commands specify IP 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 communication server to ignore all routing updates from communication servers for which an explicit distance has not been set. The second distance router configuration command sets the administrative distance for all communication servers on the Class C network 192.31.7.0 to 90. The third distance router configuration command sets the administrative distance for the communication server 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

Related Command

show ip protocols

Syntax Description

Default

Disabled

Command Mode

Router configuration

Usage Guidelines

If no interface is specified, the access list will be applied to all incoming updates.

Example

The following example causes only two networks to be accepted by a RIP routing process: network 0.0.0.0 (the RIP default) 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 rip
network 131.108.0.0
distribute-list 1 in

Related Commands

A dagger (†) indicates that the command is documented in another chapter.

access-list †
distribute-list out
redistribute

Syntax Description

Default

Disabled

Command Mode

Router configuration

Usage Guidelines

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.

Examples

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

Related Commands

A dagger (†) indicates that the command is documented in another chapter.

access-list †
distribute-list in
redistribute

Syntax Description

Default

Disabled

Command Mode

Interface configuration

Usage Guidelines

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.

Example

The following example specifies 131.108.1.27 as the primary address and 192.31.7.17 as a secondary address for Ethernet interface 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

Syntax Description

Default

No access lists are defined.

Command Mode

Global configuration

Usage Guidelines

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.

Example

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

Related Commands

neighbor distribute-list
neighbor filter-list

Syntax Description

Default

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.

Command Mode

Global configuration

Example

In the following example, the communication server 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

Related Command

set community

Syntax Description

Default

If the communication server has a directly connected interface onto the specified network, the dynamic routing protocols running on that communication server 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.

Command Mode

Global configuration

Usage Guidelines

The communication server 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 specified subnet.

Examples

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 communication server not connected to network 129.140.0.0, the communication server 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

Related Command

show ip route

Syntax Description

Default

All destinations are accepted with a distance of 0.

Command Mode

Interface configuration

Usage Guidelines

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

Example

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

Related Commands

A dagger (†) indicates that the command is documented in another chapter.

distance
ip dvmrp metric
show ip dvmrp route
tunnel mode ^†

Syntax Description

Default

Disabled

Command Mode

Interface configuration

Usage Guidelines

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.

Example

The following example configures the communication server to advertise network 0.0.0.0, in addition to other networks, to DVMRP neighbors:

ip dvmrp default-information originate

Related Command

ip dvmrp metric

Syntax Description

Default

No metric is preconfigured. Only directly connected subnets and networks are advertised to neighboring DVMRP communication servers.

Command Mode

Interface configuration

Usage Guidelines

When PIM is configured on an interface and DVMRP neighbors are discovered, the communication server 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.

If you do not specify this command, only directly connected subnets are advertised via DVMRP.

To display DVMRP activity, use the debug ip dvmrp command.

Example

The following example connects a PIM cloud to a DVMRP cloud. Access list 1 permits the sending of DVMRP reports to the DVMRP communication servers 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

Related Commands

A dagger (†) indicates that the command is documented in the Debug Command Reference publication.

debug ip dvmrp ^†
ip dvmrp accept-filter

Syntax Description

Default

priority = 100
reporttime = 5 seconds for broadcast media; 0 for nonbroadcast media
holdtime = 15 seconds

Command Mode

Interface configuration

Usage Guidelines

When enabled on an interface, GDP updates report the primary and secondary IP addresses of that interface.

Example

In the following example, GDP is enabled on Ethernet interface 1 with a report time of 10 seconds, and priority and hold time set to their defaults (because none are specified):

interface ethernet 1
ip gdp reporttime 10

Syntax Description

Default

5 seconds

Command Mode

Interface configuration

Example

The following example sets the hello interval for Ethernet interface 0 to 10 seconds:

interface ethernet 0
ip hello-interval eigrp 109 10

Related Command

ip hold-time eigrp

Syntax Description

Default

15 seconds

Command Mode

Interface configuration

Usage Guidelines

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 communication server does not receive a hello packet within the specified hold time, routes through the communication server are considered available.

Increasing the hold time delays route convergence across the network.

Example

The following example sets the hold time for Ethernet interface 0 to 40 seconds:

interface ethernet 0
ip hold-time eigrp 109 40

Related Command

ip hello-interval eigrp

Syntax Description

Default

All groups are allowed on an interface.

Command Mode

Interface configuration

Example

In the following example, host services 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

Related Command

ip igmp join-group

Syntax Description

Default

No multicast group memberships are predefined.

Command Mode

Interface configuration

Usage Guidelines

IP packets that are addressed to the group address are passed to the IP client process in the communication server.

If all the multicast-capable communication servers that you administer are members of a multicast group, pinging that group causes all communication servers to respond. This can be a useful administrative and debugging tool.

Another reason to have a communication server 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 communication server join the multicast group causes upstream communication servers to maintain multicast routing table information for that group and keeps the paths for that group active.

Example

In the following example, the communication server joins multicast group 225.2.2.2:

ip igmp join-group 225.2.2.2

Related Commands

A dagger (†) indicates that the command is documented in another chapter.

ip igmp access-group
ping ^†

Syntax Description

Default

60 seconds

Command Mode

Interface configuration

Usage Guidelines

Multicast communication servers send host membership query messages (referred to as host-query messages) to discover which multicast groups have members on the communication server'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 communication server that sends IGMP host-query messages. The designated router is elected according to the multicast routing protocol that runs on the LAN.

Example

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

Related Commands

ip pim query-interval
show ip igmp groups

Syntax Description

Default

Disabled

When enabled, IRDP uses these defaults:

• Broadcast IRDP advertisements
  
  
• Maximum interval between advertisements: 600 seconds
  
  
• Minimum interval between advertisements: 0.75 times maxadvertinterval
  
  
• Preference: 0
  
  

Command Mode

Interface configuration

Usage Guidelines

If you change maxadvertinterval, the other two values also change, so it is important to change maxadvertinterval first before changing either holdtime or minadvertinterval.

Example

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 communication server 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 communication server 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

Syntax Description

This command has no keywords or arguments.

Default

IP multicast routing is disabled.

Command Mode

Global configuration

Usage Guidelines

When IP multicast routing is disabled, the communication server does not forward any multicast packets.

Example

The following example enables IP multicast routing on the communication server:

ip multicast-routing

Related Command

ip pim

Syntax Description

Default

0, which means that all multicast packets are forwarded on the interface.

Command Mode

Interface configuration

Usage Guidelines

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, communication servers on which you configure a TTL threshold value automatically become border routers.

Example

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
 

Syntax Description

Default

No password is specified.

Command Mode

Interface configuration

Usage Guidelines

The password created by this command is used as a "key" that is inserted directly into the OSPF header when the communication server originates routing protocol packets. A separate password can be assigned to each network on a per-interface basis. All neighboring communication servers on the same network must have the same password to be able to exchange OSPF information.

Example

In the following example, the authentication key is enabled with the string yourpass:

ip ospf authentication-key yourpass

Related Command

area authentication

Syntax Description

Default

No default cost is predefined.

Command Mode

Interface configuration

Usage Guidelines

Unlike IGRP, you must set this metric manually using this command, if you need to change the default. Changing the bandwidth does not change the link cost.

The link state metric is advertised as the link cost in the communication server's router link advertisement. We do not support Type of Service (TOS), so you can assign only one cost per interface.

In general, the path cost is calculated as follows:

     10⁸ ÷ Bandwidth

Using the above formula, the default path costs were calculated as noted in the following list. If these values do not suit your network, you can use your own method of calculating path costs.

• 56-kbps Serial Link—Default cost is 1785
  
  
• 64-kbps Serial Link—Default cost is 1562
  
  
• T1 (1.544-Mbps Serial Link)—Default cost is 65
  
  
• E1 (2.048-Mbps Serial Link)—Default cost is 48
  
  
• 4-Mbps Token Ring—Default cost is 25
  
  
• Ethernet—Default cost is 10
  
  
• 16-Mbps Token Ring—Default cost is 6
  
  
• FDDI—Default cost is 1
  
  

Example

The following example sets the interface cost value to 65:

ip ospf cost 65

Syntax Description

Default

Four times the interval set for the ip ospf hello-interval command

Command Mode

Interface configuration

Usage Guidelines

The interval is advertised in the communication server's Hello packets. This value must be the same for all communication servers on a specific network.

Example

The following example sets the OSPF dead interval to 60 seconds:

interface ethernet 1

ip ospf dead-interval 60

Related Command

ip ospf hello-interval

Syntax Description

Default

10 seconds

Command Mode

Interface configuration

Usage Guidelines

This value is advertised in the communication server's Hello packets. The smaller the Hello interval, the faster topological changes will be detected, but more routing traffic will ensue. This value must be the same for all communication servers on a specific network.

Example

The following example sets the interval between Hello packets to 15 seconds:

interface ethernet 1
ip ospf hello-interval 15

Related Command

ip ospf dead-interval

Syntax Description

Default

Depends on the network type

Command Mode

Interface configuration

Usage Guidelines

Using this feature, you can configure broadcast networks as nonbroadcast multiaccess networks when, for example, you have communication servers in your network that do not support multicast addressing. You can also configure nonbroadcast multiaccess networks, such as X.25, Frame Relay, and SMDS, as broadcast networks. This feature saves you from having to configure neighbors.

If this command is issued on an interface that does not allow it, it will be ignored.

Example

The following example sets your OSPF network as a broadcast network:

interface serial 0

ip address 160.89.77.17 255.255.255.0
ip ospf network broadcast
encapsulation frame-relay

Related Commands

A dagger (†) indicates that the command is documented in another chapter.

frame-relay map ^†
neighbor (OSPF)
x25-map ^†

Syntax Description

Default

Priority of 1

Command Mode

Interface configuration

Usage Guidelines

When two communication servers attached to a network both attempt to become the designated communication server; the one with the higher priority takes precedence. If there is a tie, the communication server with the higher ID takes precedence. A communication server with a priority set to zero is ineligible to become the designated communication server or backup designated communication server. Communication server priority is only configured for interfaces to multiaccess networks (in other words, not point-to-point networks).

This priority value is used when you configure OSPF for nonbroadcast networks using the neighbor router configuration command for OSPF.

Example

The following example sets the communication server priority value to 4:

interface ethernet 0

ip ospf priority 4

Related Commands

ip ospf network
neighbor (OSPF)

Syntax Description

Default

5 seconds

Command Mode

Interface configuration

Usage Guidelines

When a communication server sends a link state advertisement (LSA) to its neighbor, it keeps the LSA until it receives back the acknowledgment. If it receives no acknowledgment in seconds, it will retransmit the LSA.

The setting of this parameter should be conservative, or needless retransmission will result. The value should be larger for serial lines and virtual links.

Example

The following example sets the retransmit-interval value to 8 seconds:

interface ethernet 2

ip ospf retransmit-interval 8

Syntax Description

Default

1 second

Command Mode

Interface configuration

Usage Guidelines

Link state advertisements in the update packet must have their age incremented by the amount specified in the seconds argument before transmission. The value assigned should take into account the transmission and propagation delays for the interface.

If the delay is not added before transmission over a link, the time in which the LSA propagates over the link is not considered. This setting has more significance on very low speed links.

Example

The following example sets the retransmit-delay value to 3 seconds:

interface ethernet 0

ip ospf transmit-delay 3

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Global configuration

Usage Guidelines

This feature makes it easier to identify a communication server because it is displayed by name rather than by its communication server ID or neighbor ID.

Example

The following example configures OSPF to look up DNS names for use in all OSPF show EXEC command displays:

ip ospf-name-lookup

Sample Display

The following is sample output of the show ip osp