- Finding Feature Information
- Restrictions for ACL IP Options Selective Drop
- Information About ACL IP Options Selective Drop
- How to Configure ACL IP Options Selective Drop
- Configuration Examples for ACL IP Options Selective Drop
- Additional References
- Feature Information for ACL IP Options Selective Drop
ACL IP Options Selective Drop
The ACL IP Options Selective Drop feature allows Cisco routers to filter packets containing IP options or to mitigate the effects of IP options on a router or downstream routers by dropping these packets or ignoring the processing of the IP options.
- Finding Feature Information
- Restrictions for ACL IP Options Selective Drop
- Information About ACL IP Options Selective Drop
- How to Configure ACL IP Options Selective Drop
- Configuration Examples for ACL IP Options Selective Drop
- Additional References
- Feature Information for ACL IP Options Selective Drop
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Restrictions for ACL IP Options Selective Drop
Resource Reservation Protocol (RSVP) (Multiprotocol Label Switching traffic engineering [MPLS TE]), Internet Group Management Protocol Version 2 (IGMPv2), and other protocols that use IP options packets may not function in drop or ignore modes.
Information About ACL IP Options Selective Drop
Using ACL IP Options Selective Drop
The ACL IP Options Selective Drop feature allows a router to filter IP options packets, thereby mitigating the effects of these packets on a router and downstream routers, and perform the following actions:
- Drop all IP options packets that it receives and prevent options from going deeper into the network.
- Ignore IP options packets destined for the router and treat them as if they had no IP options.
For many users, dropping the packets is the best solution. However, in environments in which some IP options may be legitimate, reducing the load that the packets present on the routers is sufficient. Therefore, users may prefer to skip options processing on the router and forward the packet as though it were pure IP.
Benefits of Using ACL IP Options Selective Drop
- Drop mode filters packets from the network and relieves downstream routers and hosts of the load from options packets.
- Drop mode minimizes loads to the Route Processor (RP) for options that require RP processing on distributed systems. Previously, the packets were always routed to or processed by the RP CPU. Now, the ignore and drop forms prevent the packets from impacting the RP performance.
How to Configure ACL IP Options Selective Drop
Configuring ACL IP Options Selective Drop
This section describes how to configure the ACL IP Options Selective Drop feature.
DETAILED STEPS
Configuration Examples for ACL IP Options Selective Drop
Example Configuring ACL IP Options Selective Drop
The following example shows how to configure the router (and downstream routers) to drop all options packets that enter the network:
Router(config)# ip options drop
% Warning:RSVP and other protocols that use IP Options packets may not function in drop or ignore modes.
end
Example Verifying ACL IP Options Selective Drop
The following sample output is displayed after using the ip options drop command:
Router# show ip traffic
IP statistics:
Rcvd: 428 total, 323 local destination
0 format errors, 0 checksum errors, 0 bad hop count
0 unknown protocol, 0 not a gateway
0 security failures, 0 bad options, 0 with options
Opts: 0 end, 0 nop, 0 basic security, 0 loose source route
0 timestamp, 0 extended security, 0 record route
0 stream ID, 0 strict source route, 0 alert, 0 cipso, 0 ump
0 other, 30 ignored
Frags: 0 reassembled, 0 timeouts, 0 couldn't reassemble
0 fragmented, 0 fragments, 0 couldn't fragment
Bcast: 0 received, 0 sent
Mcast: 323 received, 809 sent
Sent: 809 generated, 591 forwarded
Drop: 0 encapsulation failed, 0 unresolved, 0 no adjacency
0 no route, 0 unicast RPF, 0 forced drop, 0 unsupported-addr
0 options denied, 0 source IP address zero
Additional References
The following sections provide references related to ACL IP Options Selective Drop.
Related Documents
| Related Topic |
Document Title |
|---|---|
| Cisco IOS commands |
|
| IP access list commands |
Cisco IOS Security Command Reference |
| Using access lists for filtering IP options |
"Creating an IP Access List to Filter IP Options, TCP Flags, or Noncontiguous Ports" |
Standards
| Standards |
Title |
|---|---|
| No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature. |
-- |
MIBs
| MIBs |
MIBs Link |
|---|---|
| No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature. |
To locate and download MIBs for selected platforms, Cisco IOS XE software releases, and feature sets, use Cisco MIB Locator found at the following URL: |
RFCs
| RFCs |
Title |
|---|---|
| No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature. |
-- |
Technical Assistance
| Description |
Link |
|---|---|
| The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password. |
Feature Information for ACL IP Options Selective Drop
The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
| Table 1 | Feature Information for ACL IP Options Selective Drop |
| Feature Name |
Releases |
Feature Information |
|---|---|---|
| ACL IP Options Selective Drop |
Cisco IOS XE Release 2.1 |
The ACL IP Options Selective Drop feature allows Cisco routers to filter packets containing IP options or to mitigate the effects of IP options on a router or downstream routers by dropping these packets or ignoring the processing of the IP options. This feature was introduced on Cisco ASR 1000 Series Aggregation Services Routers. The following command was introduced: ip options. |
Cisco and the Cisco logo are trademarks or registered trademarks of Cisco and/or its affiliates in the U.S. and other countries. To view a list of Cisco trademarks, go to this URL: www.cisco.com/go/trademarks. Third-party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1110R)
Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.
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