Cisco 8851 Administration Guide

https://www.cisco.com/en/US/tech/tk648/tk361/technologies_tech_note09186a00800f0804.shtml
Verify DNS Settings
Procedure
Step 1 Select Admin Settings > Network Setup > Ethernet Setup > IPv4 Setup
Step 2 Check that the DNS Server 1 field is set correctly.
Additional Troubleshooting Information
If you have additional questions about troubleshooting your phone, go to the following Cisco website and
navigate to the desired phone model:
https://www.cisco.com/cisco/web/psa/troubleshoot.html
Cisco IP Phone 8800 Series Multiplatform Phones Administration Guide
361
Cisco IP Phone Troubleshooting
Verify DNS Settings

Cisco 8851 Specifications

General

Resolution	800 x 480 pixels
Network Interfaces	Dual Gigabit Ethernet ports
Headset Port	Yes
Audio	Wideband audio
Ethernet	10/100/1000 Mbps
USB	Yes, USB 2.0
Power	IEEE 802.3af/at Power over Ethernet (PoE)
Protocols	SIP
PoE	Yes
Codec Support	G.711, G.722, G.729, iLBC
Headset Connector	RJ9
Lines	Up to 5 lines
Dimensions	229 x 256 x 41 mm (excluding foot stand)
Weight	1.2 kg