
Chapter 24
| Multicast Filtering Commands
IGMP Snooping
– 644 –
ip igmp snooping
router-alert-option-
check
This command discards any IGMPv2/v3 packets that do not include the Router
Alert option. Use the
no
form to ignore the Router Alert Option when receiving
IGMP messages.
Syntax
[
no
]
ip igmp snooping router-alert-option-check
Default Setting
Disabled
Command Mode
Global Configuration
Command Usage
As described in Section 9.1 of RFC 3376 for IGMP Version 3, the Router Alert Option
can be used to protect against DOS attacks. One common method of attack is
launched by an intruder who takes over the role of querier, and starts overloading
multicast hosts by sending a large number of group-and-source-specific queries,
each with a large source list and the Maximum Response Time set to a large value.
To protect against this kind of attack, (1) routers should not forward queries. This is
easier to accomplish if the query carries the Router Alert option. (2) Also, when the
switch is acting in the role of a multicast host (such as when using proxy routing), it
should ignore version 2 or 3 queries that do not contain the Router Alert option.
Example
Console(config)#ip igmp snooping router-alert-option-check
Console(config)#
ip igmp snooping
router-port-expire-
time
This command configures the querier timeout. Use the
no
form to restore the
default.
Syntax
ip igmp snooping router-port-expire-time
seconds
no ip igmp snooping router-port-expire-time
seconds
- The time the switch waits after the previous querier stops before
it considers it to have expired. (Range: 1-65535;
Recommended Range: 300-500)
Default Setting
300 seconds
Command Mode
Global Configuration
Содержание ECS4120-28F
Страница 36: ...Contents 36...
Страница 38: ...Figures 38...
Страница 46: ...Section I Getting Started 46...
Страница 70: ...Chapter 1 Initial Switch Configuration Setting the System Clock 70...
Страница 86: ...Chapter 2 Using the Command Line Interface CLI Command Groups 86...
Страница 202: ...Chapter 5 SNMP Commands Additional Trap Commands 202...
Страница 210: ...Chapter 6 Remote Monitoring Commands 210...
Страница 216: ...Chapter 7 Flow Sampling Commands 216...
Страница 278: ...Chapter 8 Authentication Commands PPPoE Intermediate Agent 278...
Страница 360: ...Chapter 9 General Security Measures Port based Traffic Segmentation 360...
Страница 384: ...Chapter 10 Access Control Lists ACL Information 384...
Страница 424: ...Chapter 11 Interface Commands Power Savings 424...
Страница 446: ...Chapter 13 Power over Ethernet Commands 446...
Страница 456: ...Chapter 14 Port Mirroring Commands RSPAN Mirroring Commands 456...
Страница 488: ...Chapter 17 UniDirectional Link Detection Commands 488...
Страница 494: ...Chapter 18 Address Table Commands 494...
Страница 554: ...Chapter 20 ERPS Commands 554...
Страница 620: ...Chapter 22 Class of Service Commands Priority Commands Layer 3 and 4 620...
Страница 638: ...Chapter 23 Quality of Service Commands 638...
Страница 772: ...Chapter 25 LLDP Commands 772...
Страница 814: ...Chapter 26 CFM Commands Delay Measure Operations 814...
Страница 826: ...Chapter 27 OAM Commands 826 1 1 00 12 CF 6A 07 F6 000084 Enabled Disabled Enabled Disabled Console...
Страница 836: ...Chapter 28 Domain Name Service Commands 836...
Страница 848: ...Chapter 29 DHCP Commands DHCP Relay Option 82 848...
Страница 902: ...Section III Appendices 902...
Страница 916: ...Glossary 916...
Страница 926: ...CLI Commands 926...
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Страница 938: ...E092017 CS R02...