Cisco 1721 ios image download

These images are automatically verified for image file integrity. The following example shows how to configure the file verify auto Cisco IOS feature:.

This argument must be used each time an image is copied to or reloaded on a Cisco IOS device if the global configuration command file verify auto is not present. Network administrators can also use the verify privileged EXEC command, originally introduced for the "MD5 File Validation" feature and updated by the "Image Verification" feature, to verify the integrity of image files that are stored locally on a device.

The following example demonstrates how to use the updated verify command on a Cisco IOS device:. In the preceding output, three MD5 hash values are displayed by the verify command. The following is an explanation of each MD5 hash value:. In certain circumstances, network administrators may consider moving an existing Cisco IOS software image file from a Cisco IOS device to an administrative workstation. Once on the administrative workstation, independent tools can be used to calculate the MD5 hash of the file.

Two options are available for administrators to perform this task. One option allows the administrator to use the Cisco IOS software in use on the device to copy the stored Cisco IOS software image file to an administrative workstation. If this process is being carried out for security reasons, administrators are advised to use a secure protocol such as SCP to transfer the file.

This process is accomplished using the copy command as illustrated in the following example:. A second and recommended option, one that provides an additional level of security, is to restart a Cisco IOS device using a known-good version of Cisco IOS software from a trusted location.

Administrators can accomplish this task using the boot system global configuration command as illustrated in the following example:. Once the network device has been restarted with a known-good Cisco IOS image, a network administrator can verify the locally stored image using the verify command or by copying the Cisco IOS software image to a remote file server for offline verification.

For additional information about copying, loading, and maintaining system images, reference the Cisco IOS Configuration Fundamentals Configuration Guide. Once a file is stored on an administrative workstation, a network administrator can verify the MD5 hash for that Cisco IOS image file using an MD5 hashing utility.

The following example demonstrates the MD5 calculation and file size display for Linux-based systems:. The following example shows the use of the fsum utility and the dir command on a Windows system:. Note: The use of the fsum utility is for illustrative purposes only and should not be interpreted as an endorsement of the tool.

Once the MD5 hash and file size for a Cisco IOS software image has been collected, network administrators can verify authenticity of the image using information provided by the Cisco IOS Upgrade Planner tool during the download process.

Network administrators must identify their Cisco IOS software release this can be done by using information obtained from output provided by the show version command and navigate through the Cisco IOS Upgrade Planner tool to locate the image in use on the Cisco IOS device.

Best practices require that network administrators know and trust the tools that can be used to verify the authenticity of a Cisco IOS software image.

This document explains those tools and highlights methods to minimize risk. Additional content produced by Security Intelligence Engineering is located in the Tactical Resources section of the Cisco Security portal.

This document is part of the Cisco Security portal. Cisco provides the official information contained on the Cisco Security portal in English only. Your use of the information in the document or materials linked from the document is at your own risk. Cisco reserves the right to change or update this document without notice at any time. Security Best Practices Cisco recommends that the following security best practices be implemented to improve the security posture of the network.

Supply Chain Integrity To minimize the risk associated with malicious code, it is important that network administrators develop and consistently apply a secure methodology for Cisco IOS software image management. When downloading a Cisco IOS software image from www. Once the image has been downloaded to an administrative workstation, the MD5 hash of the local file should be verified against the hash presented by the Cisco IOS Upgrade Planner.

Once the Cisco IOS software image file has been verified as authentic and unaltered, copy it to write-once media or media that can be rendered as read-only after the image has been written. Verify the MD5 hash of the file written to the read-only media to detect corruption during the copy process. Remove the local file on the administrative workstation. Transfer the Cisco IOS software image from the file server to the Cisco IOS device using a secure protocol that provides both authentication and encryption.

The following sample output from the show version command indicates the version number. The Cisco IOS software is packaged in feature sets consisting of software images, depending on the platform. Each feature set contains a specific set of Cisco IOS features.

Release For example, " If a cell in this column is empty, the feature was included in a previous release or in the initial base release. Note These feature set tables contain only a selected list of features, which are cumulative for Release The following sections list the new hardware and software features supported by the Cisco series routers for Release The following sections describe the new hardware features supported by the Cisco series routers for Release This two port Foreign Exchange Station FXS voice interface card VIC is a newer version of the existing card that can be used for connecting directly to a standard telephone, fax machine, or similar device, and supplies ring, voltage, and dial tone.

Ports on this VIC are color-coded gray. This module also provides V phantom power to PBXs and key switches that require it. The typical application of BRI-NT allows enterprise customers with a large installed base of legacy telephony equipment to bypass the public telephone network.

This card gives users the flexibility to configure the BRI port to either the user side or the network side. When configured as the network side, the router provides ISDN network-side services. Users with all types of PBXs can send calls through a Cisco router and deliver those calls across the customer network. However, note that the older card does not provide phantom power. The customer's connection can take a clock source from one port on any of these interfaces applies to both the original and new hardware and source that clock to any of the other interfaces.

It is possible to support NT and TE on the same module. The consideration is to ensure that clocking is configured correctly. The only consideration is to ensure that clocking is configured correctly so that no clock collision occurs.

Even though the router is acting as the network side, an ISDN phone is not supported and thus should not be connected directly to the BRI ports on the router. Other switch types will only be supported as user side. The PBX is usually is the trunk circuit side and the telco, CO, or Cisco voice enabled platform is the signaling unit side. This is the interface a standard telephone provides. The FXO is on the switch end of the connection. It plugs directly into the line side of the switch so the switch thinks the FXO interface is a telephone.

Ports on this VIC are color-coded pink. The FXO sits on the switch end of the connection. The following sections describe the new software features supported by the Cisco series routers for Release The internationalization and localization enhancements in Cisco CallManager 3.

This will enable users to invoke network-specific services and facilities on a call-by-call basis when a user dials the route pattern. B2b mode is working okay. Workaround Use b2b mode. Symptom CME does not send a 3xx message during call fwd if there was a call-transfer invoked before the call-forward happens. Therefore, when a transfer is done before a forward to voicemail happens, the CME does not send a 3xx.

Conditions The call goes through fine, and the caller can leave a message for B, but DTMF fails even if signaling shows that payload was negotiated for the SIP trunk. So if the caller wants to re-record or mark the message urgent, it does not work, although the message gets recorded. Symptom : Ephone DNs gets stuck in seize state under certain conditions, particularly under the following sequence:. Conditions : The rootcause of the issue was narrowed down to trunkdial flag that is part of the skinnyCB structure which is maintained per-phone.

So, when DN2 goes offhook this trunkdial flag is set. So, all state transitions are ignored for DN1 when the call is being cleared because the trunkdial flag is set for the entire phone rather than the specific DN. Make the trunkdial flag per-DN specific rather than per-phone.

Workaround A workaround is to ensure that the ip rtp priority or ip rtp reserve command is removed before deleting the interface. Symptom Cisco IOS router running The symptom is: show proc mem 1 output seeing the first allocator's memory count is keep growing, and never decrease.

Specifically when the router is doing decryption, then send the decrypted packet to BVI interface. Symptom NAT overloading from inside source address to an outside interface may fail. Conditions The symptom was seen when translation ports were specified in an access-list associated to a route map and a second static NAT translation condition. Traffic which should have been NATed via the primary NAT overload statement failed because of the specified translation ports being used in second NAT translation condition.

This occurred even though the traffic to be NATed did not meet the conditions of the second static NAT translation condition. Workaround Remove the ip nat inside source interface X overload statement and then re-add it. The AT translations will then worked correctly until the next router reload. Conditions If another call is dropped during trunk dialing, the DN for this terminated call would move to seized state.

To work around the one-way audio issue, the call needs to be transferred out and then transferred back. This causes them to be dropped. Conditions Symptom is observed in IOS version It only affects packets which are not multilink encapsulated due to the bundle only having a single link. Workaround Either disable multilink PPP, or use the ppp multilink fragment delay interface command to force multilink headers to be applied to all outbound packets. Symptom A Cisco router may reload unexpectedly with a bus error exception.

Symptom A serial link goes down. The CEM interface will not come up. Symptom IP address removal from a physical interface. Workaround Use cryptomaps, wit vtis, to configure the ip address on the physical interface and re attempt connection. Conditions This problem occurs when the router has IPS Intrusion Prevention Systems configured, and one or more attack signatures has the denyFlowInline action enabled. Symptom The bandwidth of a multilink group interface that is down does not reflect the actual bandwidths of the links that are configured as members of the multilink group.

In earlier versions, the bandwidth is restored to Kbps. Conditions This symptom is observed when the multilink interface is down. The bandwidth is correct when the multilink bundle is up. Symptom Default route withdrawn message is send from BR immediately after successful control of default roue.

The bug is limited to default route prefix only. Workaround Use non-default route prefix. Symptom System may crash during bootup. Workaround Reduce IO memory in the configuration. Workaround The workaround of this issue is configuring timers lsa arrival and timers throttle lsa all or timers lsa-interval.

Symptom A few inconsistent error message. Symptom Under some conditions redistributed static routes are sent out with metric The rip update is sent out to a subnet within the same major network that the prefix of the static is about.

Workaround Enable the next-hop network under rip. Configure distribute-list to filter the update. Conditions The router must be configured with crpyto PKI trustpoints. Workaround Because this is a 1 byte redzone overrun, the following will prevent the crashes, and will display error messages instead. First, to prevent the usage of chunks, configure no memory lite. Second, configure exception memory ignore overflow processor to correct the redzone overrun.

Symptom Pickup will result in alerting from the pickup target instead of connected. Conditions Two calls come into a trunk monitor dn. The first one to come in is answered. The second one is then answered on the same phone using the line button. Another phone uses the pickup softkey to dial the first incoming call, which is now on hold. Workaround This issue only appears to occur on the second scenario of the above after a router reload.

This can be performed by configuring the maximum number of transcoding sessions to a value such that it would require a multiple of DSP credits.