Show mac address table cisco catos

Support for jumbo and baby giants on Catalyst switches varies by switch platform, sometimes even by modules within the switch.

Thursday, March 29, 2007

The software version is also a factor. Check the end device by pinging from the directly connected switch first, then work your way back port by port, interface by interface, trunk by trunk until you find the source of the connectivity issue. If the end device is on a different VLAN from where you are trying to ping, a L3 switch or router must be configured to allow the devices to communicate.


  • Solved: Mac Address Table in Catalyst - Cisco Community.
  • Looking for MAC-address table in CATOS - Cisco Community.
  • Thursday, March 29, 2007.
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Check the IP address, subnet mask, default gateway, dynamic routing protocol configuration, static routes, etc. If stations are not able to talk to their primary servers when connecting through a switch, the problem can involve delays on the switch port becoming active after the physical layer link comes up. In some cases, these delays can be up to 50 seconds.

Some workstations simply cannot wait this long before finding their server without giving up. All of these protocols can be disabled for access ports where they are not needed, so the switch port or interface starts forwarding packets a few seconds after it establishes a link with its neighbor device. This command sets the trunking and channel modes to off and puts the port in a STP forwarding state.

Warning : Spantree port fast start should only be enabled on ports connected.

Gratuitous ARP and Basics of Connecting a Cisco IOS Switch with a Cisco CatOS Switch

Connecting hubs, concentrators, switches, bridges, etc. In current versions of CatOS, you still have the option to use only this command, but this requires that you turn off trunking and etherchannel separately to help fix workstation startup delays.


  • Mac address table command.
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Check the Command Reference for your release of software to verify the availability of this command. If you have a large amount of alignment errors, FCS errors, or late collisions, this can indicate one of these:. Duplex Mismatch. Bad or Damaged Cable. NIC Card Issues. This can occur when manually hardcoding the speed and duplex or from autonegotiation issues between the two devices. CDP is useful to detect errors, as well as port and system statistics on nearby Cisco devices. The example shows the log messages that result from a duplex mismatch between two Catalyst series switches: one that runs CatOS, and the other that runs Cisco IOS.

These messages generally tell you what the mismatch is and where it occurs. If the switch port receives a lot of late collisions, this usually indicates a duplex mismatch problem and can result in the port being placed in an errdisable status. The half duplex side only expects packets at certain times, not at any time, and therefore counts packets received at the wrong time as collisions. There are other causes for late collisions besides duplex mismatch but this is one of the most common reasons. Hardware is C6k Mb So, for example, a file with the name "catsup.

A file with the name "catsup2. The Download Software Area registered customers only now incorporates these images. For the user, there is only one image to load into Flash. The image categories in the Download Software Area registered customers only are:.

Solved: Locating MAC addresses on a switch - Cisco Community

Note : In Hybrid mode, issue the show version command on the respective modules to determine the current image they are running. The default interface configuration for an L2 switch port is different than in CatOS. For example, when a port has an L2 port configuration, the trunk mode is desirable instead of auto. The show interface interface switchport command provides details on the current configuration of an L2 switch port. Here is an example:.

Find the IP Address of a Device connected to a Cisco Switch

Dynamic : Sets the interface to dynamically negotiate for access or trunk mode. Two options for this setting are:. Desirable : This configuration allows the port to become trunk if the neighbor device has a trunk configuration in the desirable or auto mode. Desirable mode is the default mode when a port has a switch port configuration. Auto : This configuration allows the port to become trunk if the other neighbor has a trunk configuration in the desirable mode. Even when a switch runs Cisco IOS Software, there is still the potential to have a large number of interfaces.

Therefore, to aid in the quick configuration of multiple ports, Cisco IOS Software allows you to configure a range of interfaces simultaneously as in CatOS. If you issue the range command, you can configure many interfaces with the same configuration quickly.

Mac address table command

Syntax is important and must be absolutely accurate. If a space is not in place, the command-line interface CLI returns a syntax error. The show interfaces trunk command displays all the interfaces that currently trunk. This command does not display ports that have a configuration to trunk but do not actively trunk:. The show interfaces trunk module number command shows all the interfaces on the specified module, regardless of trunk status.

The show interfaces status command provides a one-line display for each interface with the status and trunking state. If all conditions are valid for the group of ports, they form a port channel.

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We can quickly confirm this as shown below. As you can see below, the MAC address entry immediately shows up on both switches. So exactly what is going on here? Why did the MAC address of the host device update on the switches on its own this time? Here, ARP is used as a simple announcement protocol. The intention of an ARP announcement is not to solicit a reply; the intent is to update any cached entries in the ARP tables of other hosts that receive the packet. However, the operation code may indicate a request or a reply because the ARP standard specifies that the opcode is only processed after the ARP table has been updated from the address fields.

As was the case in this lab with the Windows XP host, many operating systems perform gratuitous ARP when connecting to a network. This helps to resolve problems which could otherwise occur; for example, if a network card is changed changing the IP to MAC address mapping and other hosts still have the old mapping in their ARP caches, communication will fail until the old ARP entry in their respective cache times-out. Interestingly, gratuitous ARP is also used by some interface drivers to provide load balancing for incoming traffic. In a team of network cards, it is used to announce a different MAC address within the team that should receive incoming packets.

You can see the gratuitous ARP packet details below.