Switch# show mac-address-table | include 0009.aabb.06e9 Or if you know the mac address and want to know which port the mac address is coming from, use the following command Switch# show mac-address-table | include Fa0/5 If you know the switch port you can use the following command Only ports which have the device connected and active will show the mac address detail. mac address of the connected device) and port number. The mac address or CAM table shows the Vlan associated with the port, MAC being learned on the port (i.e. With the command, you can figure out which MAC address is on which port. The bogus static ARP entry is removed, and the firewall relearns an ARP entry based on dynamic information from the host.Total Mac Addresses for this criterion: 5 After that is done, remove the command that was just used. If you decide to clear the ARP cache, you should do so only during a maintenance time when the network is not busy otherwise, there might be a pause in network traffic passing through the firewall while the ARP cache is being rebuilt.Īlthough you cannot clear individual ARP cache entries, you can configure a static ARP entry for the IP address in question so that it is paired with a bogus MAC address. If this happens, you can clear the entire ARP cache contents by using the clear arp EXEC command. If a host's IP address changes or its network interface is replaced, an existing ARP entry can become stale and will be stuck in the firewall's ARP table until it expires. Interface collision ARPs Received: 0 ARP-defense Gratuitous ARPS sent: 0 Total ARP retries: 70 Unresolved hosts: 0 Maximum Unresolved hosts: 2 Firewall# Consider the following output:įirewall# show arp statistics Number of ARP entries: PIX : 11ĭropped blocks in ARP: 10 Maximum Queued blocks: 17 Queued blocks: 0 You can add the statistics keyword to display counters for various ARP activities. You can set the persistence timer to seconds (1 to 1,215,752 seconds for PIX 6.3 or 60 to 4,294,967 seconds for ASA and FWSM). By default, ARP entries are held for 14,400 seconds (4 hours). During this time, no new ARP information is added or changed for a specific cached host address. Its MAC address and IP address are 841 and 192.168.1.199, respectively:įirewall(config)# arp inside 841 192.168.1.199ĪRP entries dynamically collected are held in the firewall's cache for a fixed length of time. Use the alias keyword to create a static proxy ARP entry, where the firewall responds to ARP requests on behalf of the configured host IP address-whether or not it actually exists.įor example, you can use the following command to configure a static ARP entry for a machine that can be found on the inside interface.
The host's IP address and MAC address (in dotted-triplet format) must also be given. Specify the firewall interface name if_name (inside or outside, for example) where the host can be found. Static ARP entries do not age out over time. There might be times when you need to configure a static entry for hosts that do not answer ARP requests on their interfaces. Define a static ARP entry:įirewall(config)# arp if name ip address mac address ĪRP entries normally are created as the firewall hears responses to ARP requests on each interface. You can use the following commands to configure ARP operations: 1. ARP is used to resolve a host's MAC address based on its IP address, and vice versa.
A firewall maintains a cache of Address Resolution Protocol (ARP) entries that are learned when it overhears ARP requests or ARP reply packets on its interfaces.
0 kommentar(er)
