2010.11.22 Cisco 6500 boot system 策略

Operational Best Practices for the Cisco Catalyst 6500 Series

2.6 Backup Cisco IOS Software and Configuration
Normal operation of the switch requires an image to boot the system. Bootable images are typically stored on the supervisor bootflash located on the supervisor module. The switch can load an OS image from local flash memory (for example, compact flash), or from a device reachable through the network such as a TFTP/FTP server. It is a good practice to have a backup copy of the current OS image located either on the supervisor flash or on a separate compact flash. Both Cisco Catalyst 6500 Series Supervisor Engine 720 and Cisco Catalyst 6500 Supervisor Engine 32 support a compact flash slot on the front panel. Should the image on bootflash be deleted accidentally or become inaccessible, locating a backup image on the flash card will save time in getting the switch back up and running.

2010.11.22 gratuitous arp

gratuitous arp的功能及影響

影響:
某一carrier isp在他的設備上,每30s送一次gratuitous arp packet, 結果呢

Gratuitous ARP could mean both gratuitous ARP request or gratuitous ARP reply. Gratuitous in this case means a request/reply that is not normally needed according to the ARP specification (RFC 826) but could be used in some cases. A gratuitous ARP request is an AddressResolutionProtocol request packet where the source and destination IP are both set to the IP of the machine issuing the packet and the destination MAC is the broadcast address ff:ff:ff:ff:ff:ff. Ordinarily, no reply packet will occur. A gratuitous ARP reply is a reply to which no request has been made.