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Function Description

4/1553-HSC 901 101/2 Uen B 2009-02-27

address. Note that the Reset-on-LAN frame has a proprietary format and

that a standard Wake-on-LAN frame will not restart the IP DSLAM.

3.2.6 DHCP Lease Time Issues

If the DHCP Server is down for a long time, the lease time of the IP

DSLAM’s IP address might expire, without the IP DSLAM being able to

renew it. In such a case, the IP DSLAM will reboot, and start with the same

scenario described in previously, that is start from Flash without an IP

address after four minutes timeout, and then keep on searching afterwards

for a DHCP Server.

Therefore it is recommended to configure the lease time of the DHCP

Server to long periods. The IP DSLAM will start to renew the lease time

after half of the lease time has passed. For example, if the lease time is set

for eight days, then the DHCP Server will have to be down for a period of

four days before the IP DSLAM will reboot.

3.2.7 Remote Storage

If an IP DSLAM reboots while the customer equipment (for example a PC)

is connected, the customer will not be able to continue the session without

requesting a new IP address (rebooting the PC or releasing the old IP

address). To address this problem, remote storage is used.

The remote storage is used for saving data that cannot be stored in Flash

and should survive a reboot.

The remote storage is used for saving the IP addresses of the Customer

Premises Equipment (CPE) and if PPPoE is used as the access method,

the MAC address of the CPE as well.

The IP DSLAM filter blocks any traffic to an IP address or MAC address it

does not know. The known IP addresses are obtained either from PEM

(static IP address) or from the DHCP traffic. After a reboot, the list will be

empty, but since the CPE already has an IP address, the CPE will not

make a new DHCP request. All traffic to and from the End-user will

therefore be blocked, until the lease time expires, or by releasing the old IP

address in the CPE, which will result in a new DHCP request issued by the

CPE. If PPPoE is used, the MAC address of the CPE is restored after a

reboot, in order to continue the PPPoE session.

The IP DSLAM uses the Domain File Server as remote storage media and

utilizes an FTP session to upload and download data from the Domain File

server, see Figure 8 on page 17.

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Ericsson EDN312 Guía de usuario Pagina 31