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Knowledge Base

Physical sub interface cannot get IP address automatic because the problem of version

Publication Date:  2019-07-09  |   Views:  739  |   Downloads:  0  |   Author:  c00222574  |   Document ID:  EKB1000014231


Issue Description

DHCP-SERVER----router----SW--- private line-----USG---

1. It cannot get IP address after configuring DHCP CLIENT ENABLE in Physical sub interface, It can get the IP address normally when PC with VLAN label encapsulation replace USG. It is found that USG sends DHCP DICOVER packets, The other side does not send OFER packets.
 Obtaining packet analysis


TTL of USG is 1, TTL of PC is 64, there is a router among users’ DHCP SERVER and USG, make DHCP RELAY on the router, the router will reduce the value of TTL, that make USG cannot receive DISCOVERY sent by USG after the DHCP SERVER sending.

Alarm Information


Handling Process

It is normal after upgrading to V100R005C00SPC600.

Root Cause

1. Check the configuration of packet filtering, normal.
2. Check the configuration of DHCP, normal.
3. Doubt the version problem.


This failure appears before the V100R005C00SPC500 version, it suggested that upgrading to V100R005C00SPC600 if this demand was required.