This indicate the the device is connected to port GigabitEthernet2/0/5. Total Mac Addresses for this criterion: 1 TB-CS-4506# sh mac address-table address # Step 3 This will show the interface (or IP) to which it is connected to a port or through which it is learned. Then, do the show mac-address command on the switch. Protocol Address Age (min) Hardware Addr Type Interface Success rate is 100 percent (5/5), round-trip min/avg/max = 1/4/9 ms Sending 5, 100-byte ICMP Echos to 142.30.15.254, timeout is 2 seconds: This command will show the MAC address of the device. If the device is pingable, then do a simple sh ip arp command. If you know the IP address of the device then try to ping it from within the switch. These commands will help you to work faster. If you see the IP and a MAC, odds are you're good.Trick and tip for network admin you should know when you work on enterprice switch. If you ping the gateway, and it doesn't answer, how can you tell it's connected? Look the arp cache, arp -a. In this case, an obvious answer exists to verify connectivity - although it had to be pointed out to me. In my environment, we use Checkpoints as the default gateways for many subnets - so to get the MAC address is a little more of a PITA - to have to shell or gui into the firewall and look at the arp table - but the concept is the same.Īs far as using ICMP to verify connectivity - again, the firewalls cause some concern to the server admins - who can't ping their gateway, because it might not respond, even though it's connected. Many enterprise network management systems include tools to help automate this process, but it's handy to remember in a pinch.Ī problem with this approach I've recently run into is using firewalls as routers. We can see that FastEthernet0/6 is an access port, which means it is most likely our host port: Next, we telnet to the neighboring switch's IP address and repeat our MAC table lookup: Interface: FastEthernet0/13, Port ID (outgoing port): FastEthernet0/13Ĭisco IOS Software, C3550 Software (C3550-IPSERVICESK9-M), Version 12.2(44)SE2, RELEASE SOFTWARE (fc2)Ĭopyright (c) 1986-2008 by Cisco Systems, Inc. Platform: Cisco WS-C3550-24, Capabilities: Switch IGMP The neighboring switch's management address is advertised via CDP: The configuration of this interface indicates that this port connects to another switch: Rather, all Ethernet packets come to the DA-MP by way of the IPFE. However, this may not necessarily be a direct connection. Switch MAC Address Cache and Ping Feature In certain deployments where all traffic passes through the IPFE, no Ethernet packets go directly to the DA-MP from the gateway (or remote peer, for the case that a remote peer is on the local network segment). Now we know that the host is reachable via interface FastEthernet0/13. port number), we need to query the MAC table: To resolve this layer two address to a layer one "address" (i.e. This tells us that the host's default router is reachable at 10.0.39.9, so we telnet or SSH to that address and perform an ARP table lookup for the host's IP address. To locate a host port by its IP address, start with a traceroute from some point inside the network, perhaps at your local workstation or a core router: A much more convenient approach, if the machine has functional connectivity, is to query the ARP and MAC tables of various infrastructure devices to find its switch port. When you need to locate the physical switch port to which a workstation or other end device is attached, one way is to physically trace and/or tone out the cable path. Early in my career I learned a troubleshooting approach to save me quite a bit of potentially painful cable tracing.
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