![]()
The new global command ip device tracking probe auto-source fallback 0.0.0.x 255.255.255.0 override allows the user to use the host address of 0.0.0.x in the subnet in order to avoid any duplicate IP address problems. It was added in order to allow a user-defined ARP request source IP address instead of the requirement to use the default source IP address of 0.0.0.0. This latest CLI command was introduced through Cisco bug ID CSCtn27420 in Cisco IOS Version 15.2(2)E. CHANGE MAC ADDRESS WINDOWS 7 REGISTRY KEY CODEHere is the command format for newer code versions: ip device tracking probe auto-source fallback CHANGE MAC ADDRESS WINDOWS 7 REGISTRY KEY SERIESThis command was implemented in Cisco IOS Version 12.2(55)SE on 2900, 3500, and 3700 Series Switch platforms, and in Version 15.1(1)SG on the 4500 Series Switch platform. SVI is not currently available on the 6500 Series Switch platform. This method is difficult to scale, so Cisco recommends that you use the IP device-tracking probe delay as the primary method. The caveat to this method is that an SVI must exist on every switch in every VLAN where Microsoft Windows clients who run DHCP reside. This configuration currently does not trigger the duplicate address detection error message in Microsoft Windows. Here is the command format for older code versions: ip device tracking probe use-svi Thus, it is certain that the duplicate IP address error will not occur. If an SVI is configured for the VLAN and either of the two commands that follow are used, then the sender IP address in the IPDT probes will never be 0.0.0.0. ![]() CHANGE MAC ADDRESS WINDOWS 7 REGISTRY KEY PCThe most effective method that is used in order to prevent this issue is to configure the switch so that it sends a non-RFC compliant ARP Probe to source the probe from the Switch Virtual Interface (SVI) in the VLAN where the PC resides. There are multiple methods that are used in order to work around this issue. Here is an example of the failed packet sequence: See also Check if network connectivity for Azure Arc Connected Machine Agent is blocked The PC does not obtain an address, and the user must either manually release/renew the address, disconnect and reconnect to the network, or reboot the PC in order to gain network access. If the switch sends out an ARP Probe for the client while the Microsoft Windows PC is in its duplicate-address detection phase, then Microsoft Windows detects the probe as a duplicate IP address and presents a message that a duplicate IP address was found on the network for 0.0.0.0. This function is critical whenever access lists are used with 802.1x or any other Flex-Auth function on Cisco switches. This IP address is then used when an Access Control List (ACL) is applied to the interface in order to substitute the source address in the ACL with the client IP address. It is used in order to activate and maintain the entry in the table after it is learned. The probe does not populate the tracking entry. The purpose of IP device tracking is for the switch to obtain and maintain a list of devices that are connected to the switch via an IP address. This can occur if two (or more) hosts have, for whatever reason, been inadvertently configured with the same address, and both are simultaneously in the process of probing that address to see if it can safely be used.Ĭisco IOS® uses the Address Resolution Protocol (ARP) Probe that is sourced from an address of 0.0.0.0 in order to maintain the IP device-tracking cache during IP device tracking, and a feature that uses it is enabled (such as 802.1x) on a Cisco IOS switch. In addition, if during this period the host receives any ARP Probe where the packet’s ‘target IP address’ is the address being probed for, and the packet’s ‘sender hardware address’ is not the hardware address of any of the host’s interfaces, then the host SHOULD similarly treat this as an address conflict and signal an error to the configuring agent as above. One of the triggers for this detection flow is defined in section 2.1.1: This new detection flow is described in RFC 5227. With Microsoft Windows Vista and later versions, Microsoft introduced a new mechanism that is used in order to detect duplicate addresses on the network when the DHCP process occurs.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |