Cisco IP Phone 6851

IP addresses to devices. Because IP addresses are a limited resource, the DHCP server periodically
renews the device lease on the IP address. If a phone loses the IP address for any reason, or if some other
device on the network is assigned the same IP address, the communication between the SIP proxy and
the phone is either severed or degraded. Whenever an expected SIP response is not received within a
programmable amount of time after the corresponding SIP command is sent, the DHCP Timeout on
Renewal parameter causes the device to request a renewal of its IP address. If the DHCP server returns
the IP address that it originally assigned to the phone, the DHCP assignment is presumed to be operating
correctly. Otherwise, the phone resets to try to fix the issue.
• Static IP—A static IP address for the phone.
Procedure
Step 1
In the phone web page, select Admin Login > advanced > Voice > System.
Step 2
In the IPv4 Settings section, use the Connection Type drop-down list box to choose the connection type:
•
Dynamic Host Configuration Protocol (DHCP)
•
Static IP
Step 3
In the IPv6 Settings section, use the Connection Type drop-down list box to choose the connection type:
•
Dynamic Host Configuration Protocol (DHCP)
•
Static IP
Step 4
If you choose Static IP, configure these settings in the Static IP Settings section:
• Static IP—Static IP address of the phone
• NetMask—Netmask of the phone
• Gateway—Gateway IP address
Step 5
Click Submit All Changes.
DHCP Option Support
The following table lists the DHCP options that are supported on the Cisco IP Phone.
DescriptionNetwork Standard
Subnet maskDHCP option 1
Time offsetDHCP option 2
RouterDHCP option 3
Domain name serverDHCP option 6
Cisco IP Phone 6800 Series Multiplatform Phones Administration Guide
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Security Features