This issue occurs because both DHCP Relay Agents responds to the DHCP requests and they don't work as fail over.
- The client sends a DHCP request and both Relay Agent send the requests to the DHCP server
- DHCP server responds to the request with restricted IP address
- The client get the response from one of the DHCP relay agent and it then send a request with SOH
- Now the response from the second DHCP relay agent comes and the client assume the IP address with restricted IP and discard the response from the both relay agent with full access IP
In the network trace, you will see:
16754 0.0000000 <Time><Date> 0.0.0.0 255.255.255.255 DHCP DHCP:Request, MsgType = REQUEST, TransactionID = 0x401B504D
16784 0.0085968 <Time><Date> 192.168.100.3 DS-CLIENTDHCP DHCP:Reply, MsgType = ACK, TransactionID = 0x401B504D
16793 0.0003589 <Time><Date> 0.0.0.0 255.255.255.255 DHCP DHCP:Request, MsgType = REQUEST, TransactionID = 0x401B504D, SOH:Vendor = Microsoft, Version 2, Request
16804 0.0004382 <Time><Date> 192.168.100.2 DS-CLIENTDHCP DHCP:Reply, MsgType = ACK, TransactionID = 0x401B504D - The client gets response from second DHCP relay agent after it sends the request with SOH and the client assumes that IP address and discard the following acknowledge.
16985 0.0201080 <Time><Date> 192.168.100.2 DS-CLIENTDHCP DHCP:Reply, MsgType = ACK, TransactionID = 0x401B504D, SOH:Vendor = Microsoft, Version 2, Response
16994 0.0153142 <Time><Date> 192.168.100.3 DS-CLIENTDHCP DHCP:Reply, MsgType = ACK, TransactionID = 0x401B504D, SOH:Vendor = Microsoft, Version 2, Response.