Ethernet not able to get dhcpoffer

Router gives the IP but Ethernet adapter not able to set automatically. I manually set the IP address or else it wont connect

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: linux-image-4.15.0-43-generic 4.15.0-43.46
ProcVersionSignature: Ubuntu 4.15.0-43.46-generic 4.15.18
Uname: Linux 4.15.0-43-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.5
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC1: gdm 1884 F.... pulseaudio
                      dove-buha 2431 F.... pulseaudio
 /dev/snd/controlC0: gdm 1884 F.... pulseaudio
                      dove-buha 2431 F.... pulseaudio
Date: Mon Dec 31 16:34:45 2018
InstallationDate: Installed on 2017-07-01 (547 days ago)
InstallationMedia: Ubuntu 17.04 "Zesty Zapus" - Release amd64 (20170412)
IwConfig:
 lo no wireless extensions.

 eth0 no wireless extensions.
MachineType: Dell Inc. Precision Tower 7810
ProcEnviron:
 LANGUAGE=en_IN:en
 TERM=xterm-256color
 PATH=(custom, no user)
 LANG=en_IN
 SHELL=/bin/bash
ProcFB: 0 radeondrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.15.0-43-generic root=UUID=b6b9f1f1-0be8-440c-ae54-a882a00b91d0 ro net.ifnames=0 biosdevname=0 quiet splash vt.handoff=7
PulseList:
 Error: command ['pacmd', 'list'] failed with exit code 1: Home directory not accessible: Permission denied
 No PulseAudio daemon running, or not running as session daemon.
RelatedPackageVersions:
 linux-restricted-modules-4.15.0-43-generic N/A
 linux-backports-modules-4.15.0-43-generic N/A
 linux-firmware 1.173.2
RfKill:

SourcePackage: linux
UpgradeStatus: Upgraded to bionic on 2018-05-29 (215 days ago)
dmi.bios.date: 05/20/2016
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A13
dmi.board.name: 0GWHMW
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 7
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA13:bd05/20/2016:svnDellInc.:pnPrecisionTower7810:pvr:rvnDellInc.:rn0GWHMW:rvrA00:cvnDellInc.:ct7:cvr:
dmi.product.name: Precision Tower 7810
dmi.sys.vendor: Dell Inc.